MI

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Type I hypersensitivity

"A": Allergic/anaphylactic/immediate IgE mediated tissue damage; Ab against allergen; mast cells; Th2 First exposure: sensitization; trigger a strong Th2 response. Mast cells coated w/ allergen-specific IgE via high affinity FceR1; subsequent exposure results in crosslinking of FceR1-IgE molecules to stimulate mast cell activation via ITAMs

Type II hypersensitivity

"C": Cell-mediated/antibody-mediate IgM, IgG mediated tissue damage; ab binds to tissue antigen (complement and FcR mediate inflamm); ab binds cell antigens (complement activation, phagocytosis); ab binds to cell antigens (abnormal physiological response w/out substantial inflam response) OFTEN AGAINST SELF-ANTIGENS; LESS COMMONLY MICROBIAL MOLECULAR MIMICRY; USUALLY NOT SYSTEMIC; DAMAGED TISSUE WHERE ANTIGEN IS FOUND

Type IV hypersensitivity

"D": delayed/T-cell mediated CD4 Th1/8 CTL mediated tissue damage; self or microbial chromic inflamm poison ivy; positive Tb test; granuloma

Type III hypersensitivity

"I": Immune complex mediated IgM, IgG mediated damage to tissue; Ig:Ag immune complexes tend to be systemic, with no specificity for a particular tissue or organ

Depending on the allele, terminal sugars on the RBC will be one of three types:

(1) N-Acetylgalactosamine (A antigen) (2)Galactose (B Antigen) (3) Neither of the above; instead abbreviated as Fructose (O antigen)

Complement regulation

DAF (decay accelerating factor): binds C3 convertase and dissociates it Soluble regulators: Factor 1 cleaves C3b into smaller fragments; C1 inhibitor

alarmins

DAMPS. *Molecules that appear or that form when normal cells are damaged by trauma or inflammatory activity.

antigen capture and processing

DCs and macrophages capture protein antigens in the tissues at the site of infection or vaccination by phagocytosis, endocytosis, or pinocytosis; viruses deliver protein antigens into the cell by infection. Antigens taken up from the extracellular environment are proteolytically degraded into antigenic peptides in phagolysosomes, and the peptides are loaded onto MHC Class II molecules (extracellular pathway of antigen presentation). Antigens that arise from inside the cells (viral proteins, self-proteins) are proteolytically degraded into antigenic peptides by proteosomes, and the peptides are loaded onto MHC Class I molecules (intracellular pathway of antigen presentation.

what has to happen to increase the odds of successful antigen presentation?

DCs must acquire a mature phenotype!

Drug interactions caused by penicillin being attached to carrier molecule and eliciting an immune response, _____.

DIHA

Identify the steps of antigen processing that are affected by Herpes simplex virus (HSV)

DNA virus is sequestered inside neurons where it maintains a life long infection. Neurons express little cell surface class I molecules providing a safe haven for viruses. Produces protein which binds to cytosolic portion of TAP. This inhibits TAP-mediated translocation of peptides from cytsol into the ER. In the absence of peptide transport to ER antigenic peptide/Class I MHC complexes do not form and infection remains undetected

Which molecules define a double positive thymocyte? (Thymic Cortex Process)

DPs are characterized by the cell surface expression of both CD4 and CD8 as well as the expression of the preTCR complex (signalling via these molecules trigger somatic recombination of the TCRa chain leading to subsequent expression of a TCR)

Define death by neglect and negative selection

Death By Neglect: When there is insignificant interactive avidity of the thymocyte with thymic epithelial cells Negative Selection: Occurs if recognition exceeds a pre-determined threshold (high avidity interaction) resulting in thymocytes being clonally eliminated or functionally inactivated. (initial elimination of potentially self reactive T cells occurs in the thymic cortex, involving TCR mediated contact with self antigen/MHC presented by thymic epithelial cells.

____ cleaves a subunit of the IL-2 receptor, interfering with the maintenance of TH1 cells and leads to TH2 cell bias

Der p1

_____ destroys intercellular tight-junction by cleaving occludin and is taken up by dendritic cells for antigen presenting

Der p1

dendritic cells

(DCs)- "professional antigen presenting cells"; are critical for stimulating primary adaptive responses.

pepsin digestion of IgG

(Fab)2 -Fc lots of segs that degrade -cleaves below disulfide bonds

Interactions that contribute to interactive avidity

(i) the intrinsic affinity of the TCR for self antigen/MHC complex (ii) the number of TCRs on T Cell (iii) the number of self antigen/MHC complexes on the thymic epithelium (APC) (iv) the number of antagonistic peptide complexes (i.e. cell/cell molecular interactions that repel one another) (v) The number of adhesion molecules

Three distinct lineages of hematopoiesis

(lymphoid, myeloid, and erythroid).

what are phagocytes and how do they work

(monocytes, macrophages, neutrophils)- destroy microbes by the process of phagocytosis and/or by production of antimicrobial substances.

What is the first step toward the activation of the Lectin Pathway?

* Lectins are proteins that recognize and bind carbs. * pathway does not depend on antibody for activation Initiated by binding of mannose-binding lectin (MBL) to mannose residues on surface of bacteria, fungi, and viruses (binds to two enzymes: MBL-associated serine protease 1 and 2 (MASP-1 and MASP-2)) (activator of pathway is MBL)

where are naive cells activated?

*****NAÏVE CELLS ACTIVATED IN SECONDARY MYPH TISSUES (SPLEEN AND LYMPH NODES)

Scavenger receptors.

*A class of receptors expressed by phagocytes that can bind many types of substances associated with microbes. Includes many receptor classes that bind a wide variety of microbial products and DAMPs, resulting in endocytosis or phagocytosis.

Neutrophil Extracellular Traps (NETS)

*A network of chromatin fibers formed from dead neutrophils that binds microbes inhibiting colonization. NETS are chromatin fibers derived from dead neutrophils that adsorb antimicrobial proteins such as defensins. NETS bind and destroy microbes to contribute to protection of the oral environment

complement system

*A system of blood proteins that carry out innate antimicrobial responses. a system of blood proteins and cell-surface receptors that cause microbial lysis, facilitates phagocytosis, and promotes inflammation.

innate immune responses

*An antimicrobial response mediated by cells and molecules present in significant numbers at birth. are not antigen-specific, occur immediately, and are carried out by phagocytes, barrier epithelial cells, and complement proteins; there is no immunological memory.

adaptive immune responses

*An antimicrobial response that develops gradually after lymphocytes are stimulated by antigens. Adaptive responses are carried out by lymphocytes (B and T cells). Two types: humoral immune responses and cell-mediated immune responses Adaptive responses are antigen-specific and tailored to the type of microbe causing the infection. adaptive responses result in immunological memory.

Defensins and cathelicidins

*Antimicrobial peptides produced by innate cells such as neutrophils and epithelial cells. Antimicrobial molecules produced by innate cells contribute to destruction of bacteria, fungi, and some viruses. small antimicrobial proteins secreted by epithelial cells and neutrophils in response to PAMPs. Bind to microbes and disrupt their cell membrane, forming pores that allow water to flow in causing lysis. Stimulate the production of reactive oxygen species (ROS) and nitric oxide (NO) by neutrophils. Contribute to inflammation by stimulating chemotaxis of macrophages and neutrophils into the site of infection.

Effector lymphocytes

*B or T cells that amass in great numbers after activation by antigen and which serve to mount destructive responses against microbes. Effector cells destroy the antigen or microbe

memory cells

*B or T cells that develop after a primary adaptive response and which remain to provide long-lasting protective immunity against repeat infection. memory cells are long-lived cells that are converted into effector cells in a secondary adaptive response. they develop more rapidly than primary responses, are more robust, and may last indefinitely

Components of Acquired immunity

*B- lymphocytes* which differentiate into plasma cells that produce antibodies. *T-lymphocytes: T-helper cells* which activate macrophages and other lymphocytes, *Cytotoxic T-cells *which kill infected or tumor targets, *Regulatory T-cells* which down-regulate, suppress or tolerize other lymphocytes.

Phagocytic and Endocytic barriers

*Blood monocytes, tissue macrophages, PMNs*. Bacteria are ingested into phagocytic vessicles and *fuse with lysosomes creating phagolysosomes* which degrade entrapped microorganisms. *Interferons Alpha and Beta* are found within nucleated cells which* inhibit viral expansion*.

TCR-CD3 Complex

*CD3 surrounds TCR chains *that allows *signal transduction* to be effective for activation of T cell once an antigen binds to the antigen-binding site.

CD8+ Cytotoxic T-lymphocytes

*CD8+* *MHC-I restricted* Mediates cell mediated immunity to: - *Viral infection, intracellular pathogens* - *Tumor cells* *Upregulated by TH1 activity* IL-2 receptors on CTLs are activated by TH-cells secretion of IL-2.

*Exogenous* Antigen Processing

*CLIP is the protein* that mediates the loading of the peptides to the MHC II molecules.

Monocytes

*Circulate in blood after leaving bone marrow for approximately 1-3 days* before entering tissues to mature into macrophages. Involved in phagocytosis and intracellular killing of microorganisms. *Generation of toxic metabolites* through *respiratory burst*. Production of *nitric oxide, hydrogen peroxide, superoxide anion*.

PMNs or polymorphic neutrophils

*First to arrive at inflammation site* and most numerous leukocyte that is a major cell type involved in the initiation of immune response, inflammation, *phagocytosis* of foreign molecules. PMNs produce *myeloperoxidases* for enhancing *oxidated antimicrobial effects*, *lactoferrin and lyzosyme* for direct antimicrobial activity, and *leukotrines and prostogalndins* to mediate vascular changes. Attracted by *chemotactic factors* stimulated by tissue damage esp *IL-8* (complement proteins, chemokines, clotting proteins).

Big 3 proinflammatory signalling molecules

*IL-1Beta* *TNF-alpha* *IL-6*

Mast Cells

*Important in allergic reactions* like basophils, BUT ONLY FOUND IN TISSUES. Contains granules with *histamine, prostaglandins, leukotrienes*.

What is the first step of the activation of complement via the Alternative Pathway?

*Like Classical Pathway, generates C5b but without the need for antigen-antibody complexes to initiate. - Initiated by cell-surface components that are foreign to the host

PAMPS (what is it, what do they do, and what are some examples of specific ones?)

*Molecules associated with microbes, usually containing repeated structures, that activate innate cells. Pathogen-associated molecular patterns consist of repeating patterns of nuclei acids, proteins, lipids, or carbohydrates common to microbes but not normal cells. bind to PRRs expressed on leukocytes and epithelial cells. ex. Lipopolysaccharide (LPS, Gram negative bacteria). Lipotechoic Acid- Gram positive bacteria. Peptidoglycan- most bacteria. Single- or double-stranded RNA (viruses)- intracellular recognition as well Mannans, glucans (fungi).

antigens

*Molecules, usually proteins, that stimulate adaptive immune responses. macromolecules that bind to antigen receptors (antibodies or T cell receptors) in a highly specific manner Antigens stimulate adaptive immune responses (T cells and B cells) In nature, antigens are often large proteins and may contain several different antigenic determinants. Protein antigens produced by, or physically associated with microbes are typically very antigenic.

Natural Killer T-Cell

*NK T-cells (different from NK-cells which are innate immune cells that rely on antibody-dependent mechanisms)*. Make up less than 0.2% of peripheral blood T Cells. Have *CD3 and TCR:* These cells recognize *lipid and glycolipid antigen.*

naive lymphocytes

*Naïve lymphocytes B or T cells that have yet to be stimulated by their specific antigen. there a very few of them, the develop slowly and fade quickly

Peyer's Patches

*Non-encapsulated lymphatic tissue.* *Have M-cells (VIP) which are specialized epithelial cells that sample antigen* from the gut. Allow the passage of antigens so that APCs can process and present antigens to T and B cells. Peyer's patches are known for IgA secretion and formation of germinal centers and lymphatic nodules.

Tonsils

*Partially encapsulated with an epithelial covering.* Usually have lots of germinal centers.

Toll-like receptors (TLRs)

*Pattern recognition receptors that regulate cell functions through activation of transcription factors. The binding of PAMPs to TLRs stimulates phagocyte activation and cytokine production regulate innate responses to microbial throughout the body including the gingival sulcus. TLRs are expressed throughout the animal kingdom and there are nine functional TLRs in humans (TLR1-9). TLRs are located on the cell surface or cytosol of many cell types including macrophages, dendritic cells, epithelial cells, and B and T cells. TLR4 binds bacterial lipopolysaccharide (LPS, aka endotoxin), which is a potent activator of macrophages and dendritic cells in response to gram negative bacteria such as E. coli.

Eosinophil

*Pink staining granulocyte* that is active in *parasitic infections and asthmatic reactions*. Eosinophils secrete enzymes that punch holes in parasitic worms. Eosinophils are also capable of phagocytosis but they are not the major phagocytotic cell.

respiratory burst

*Production of reactive oxygen species by phagocytic cells. Respiratory burst leads to oxidative stress- refers to reactice oxygen species- extremely damaging. Short lived reactive and toxic to pathogens, but also wear down our cells and tissues the generation of toxic reactive oxygen species (ROS); is regulated by phagocyte oxidase in the phagocyte cell membrane. Phagocyte oxidase (aka NADPH oxidase) is activated by PAMPs and uses molecular oxygen to generate superoxide anion, inside and outside of the cell Superoxide anion produced within the cell is quickly converted to other ROS by the enzymes superoxide dismutase and myeloperoxidase Mutations in phagocyte oxidase result in chronic granulomatous disease, which is associated with increased risk of bacterial infections. ROS kill by disrupting cell membranes, enzymes, and nucleic acids

antibodies

*Protein molecules that bind antigens in a highly specific manner.

Antigen Receptor

*Receptors expressed by lymphocytes that bind antigens in a highly specific manner. An antimicrobial response mediated by cells and molecules present in significant numbers at birth.

PRRs

*Receptors on most cell types, especially phagocytes and epithelial cells, that bind PAMPs and DAMPs resulting in cellular activation. pattern recognition receptors- expressed on leukocytes and epithelial cells. ex. TLRs, N-formyl peptide receptors, C-type lectin receptors, and Scavenger receptors

Neutrophil reactivity during inflammation

*Respiratory burst, production of reactive oxygen and nitrogen intermediates*, release of primary and secondary granules with *proteases, phospholipases, elastases, and collagenases* to *destroy some host tissues to penetrate deeper* to sites of infection and inflammation. *Myeloperoxidses* to assist oxidated antimicrobial effects. *Lectoferrin and lysozyme* production (direct antimicrobial agents) *Leukotrienes and Prostaglandin* to mediate* vascular function.*

secondary adaptive response

*Response resulting from activation of memory lymphocytes. occurs following a second or third, etc. exposure to the same antigen that elicited the primary response and is carried out by memory B and T cells.

primary adaptive response

*Response resulting from activation of naïve lymphocytes. occurs upon the first exposure to a specific antigen and begins with activation of naïve B and T cells.

Anatomic barriers of innate immunity

*Skin*: thin outer epidermis, and thicker underlying dermis. Impedes entry of foreign material. *Sebaceous glands*: produce* sebum, comprised of lactic acid* and fatty acids which *reduce skin pH* inhibiting microbial growth. *Mucous membranes*: covered by cilla, serve to trap organisms and propels them out of the body.

*T-lymph intracellular pathogen* response

*T-cells have evolved to handle intracellular pathogens* whereas *B cells recognize extracellular pathogens.* T-cells recognize small antigenic determinants expressed on the surface of host cells associated with MHC molecules (major histocompatibility complex)

*Endogenous* Antigen Processing

*TAP (transporter of antigenic peptides)* needed to transport antigens to the cell surface.

TH1 Cells

*TH1 cells helps to promote activation of cell mediated immunity to INTRACELLULAR pathogens.* Secretes: 1. IL-2 2. IFN-gamma 3. TNF-Beta

TH2 Cells

*TH2 Cells promote activation and optimization of humoral mediated immunity *to *EXTRACELLULAR PATHOGENS.* Secretes: IL-4, 5, 10, 13.

Antiviral response

*The innate response to viruses mediated by type I interferons viral replication in healthy cells is inhibited by Type I interferons (IFN-a and IFN-b) produced by virus-infected epithelial cells.

antigenic determinant

*The molecular portion of an antigen recognized by antigen receptors. The specific region of an antigen that binds to an antigen receptor

phagocytosis

*The receptor-mediated process of engulfment of microbes or other large entities.

endocytosis

*The receptor-mediated process of uptake of molecular substances.

Facts about Localized anaphylaxis:

- Allergic rhinitis aka hay fever: from pollens or dust mite feces inhaled and they react with IgE molecules bound to sensitized mast cells in the conjunctivae and nasal mucosa. This cross-linking causes release of histamine and heparin from mast cells. Symptoms are mild. - Bronchial asthma: same as above but in bronchioles. Contraction of smooth muscle, mucous secretion, and constriction of bronchioles. - Wheal and flare: from insect bites or allergy testing (will show in 5-7 min). Cause localized increase in blood flow and vascular permeability from localized release of histamine from activated mast cells.

localized anaphylaxis:

What are the activators involved in the Classical pathway?

- Antibodies: activate complement (IgM and IgG3 are strongest activators) - C reactive protein (CRP) * - must bind to at least two Fc sites on the Ig molecule to be activated ---Circulating IgM has no Fc sites exposed for binding ; but pentameric IgM is bound to a surface and has at least 3 binding sites for C1q ---IgG has only 1 Fc site in the CH2 domain, therefore C1q binding only occurs when two IgG molecules are within 40nm of each other and each bind C1q *IgM is therefore the best activator of complement

Discuss the various steps and the anatomic sites involved in B cell activation, proliferation and differentiation in peripheral lymph nodes

- Antigen-Antibody complexes enter the lymph nodes - B cells and T cells activated in the paracortex - Activated B cells migrate to the primary follicles in the cortex - As cell proliferation continues, a secondary follicle is formed and some activated B cells migrate to the germinal center - In germinal center, B cells differentiate into plasma cells and memory cells - Plasma cells migrate to the medulla and then go into circulation Germinal Center: activated B cell undergoes proliferation in dark zone proliferating B cells are called centroblasts These centroblasts are large in size, diffuse chromatin, and low mIg when cell division stops, they are called centrocytes centrocytes are small, non-dividing, and have mIg they contact the antigen in the light zone

Generalized rxns to circulating immune complexes cause many other effects including:

- Autoimmune diseases: Lupus Rheumatoid arthritis Goodpasture's syndrome - Drug interactions: Allergies to penicillins and sulfonamides - Infectious diseases: post-Strep A glomerulonephritis Hepatitis Meningitis Mononuleosis (Mono) Malaria Trypanosomiasis

B cell internalization and display of foreign antigens

- B cells can take up exogenous antigen via binding through their surface Ig in a receptor mediated endocytotic mechanism. - Proteins are internalized, broken down to peptides. - Peptides are presented on the B cell surface held in the peptide binding grooves of MHC class II.

Progenitor T cells express:

- C-Kit - a receptor for stem cell growth factor - CD44 (adhesion molecule - homing) - CD25 - α chain for IL-2 receptor ** No CD markers (DN)

What are the inhibitors of the Lectin Pathway?

- C3 convertase inhibitors Factor I: cleaves C4b to prevent C3 convertase - Decay accelerating factor (DAF): has ability to dissociate C3 convertase ** Saialic acid residues present on the surface of mammalian cells prevent MBL binding to mannose residues

Describe the composition of the CD3 co-receptor and how it associated with TCR:

- CD3 is a complex of 5 chains organized to form 3 dimers: 5 chains: γ, ε, δ are in Ig superfamily, ζ and η are not Heterodimers of γε, δε, and ζη Homodimer: ζζ (90% of CD3 complexes) --ζη heterodimer accounts for other 10% - Transmembrane(TM) region of all CD3 chains is negatively charged due to aspartic acid residue -> interact with positively charged transmembrane domains of the TCR chains - Cytoplasmic domain of all CD3 chains have an immuno receptor tyrosine-based activation motif (ITAM) --> these motifs are important in signal transduction. γ, ε, δ chains contain 1 ITAM, whereas ζ and η chains have 3 ITAMS.

What may be the bad effect of increased secretion of IFN-γ, and subsequent recruiting and activation of more macrophages?

- Can lead to granuloma formation and multinucleate giant cells, release lots of lytic enzymes destroying surrounding cells - TB induces this from prolonged inflammation

Type IV facts

- Cell mediated - Sensitized Th1 release Cytokines that activate macrophages or Tc that induce direct cellular damage - Th2 and CTLs mediate similar responses - Typically includes dermatitis, tubercular lesions, and graft rejection

Type IV Hypersensitivity Mechanism:

- Delayed type; Cell mediated - induced by a variety of intracellular pathogens such as Mycobacterium tuberculosis (bacteria), Candida albicans (fungus), Leishmania (protozoa), and Herpes virus. - Sensitized TH1 release Cytokines that activate macrophages or Tc that induce direct cellular damage - TH2 and CTLs mediate similar responses Process: 1. The initial phase of antigen contact: - Antigen processed by APCs and presented via MHC class II to TH cells---> TH proliferate and differentiate into TH1 (~1-2 weeks for sensitization to occur) 2. TH1 secrete a variety of cytokines after re-exposure to antigen, factors attract and activate macrophages, which function as primary effector cells in DTH *(~48-72 hrs for effector phase to peak after secondary contact) - Only 5% of cells are antigen specific Th1, the rest are macrophages and non-specific cells - Th1 cells release IL-3 and GM-CSF, induces hematopoiesis and granulocyte-monocyte lineage of cells - IFN-gamma and TNF-beta (and macrophage derived TNF-alpha and IL-1) induce changes in nearby endothelial cells causing them to express adhesion molecules so leukocytes can adhere and move. - Monocytes are attracted to the site by monocyte chemotactic factor (MCP-1/CCL2) at 24-48 hours and become terminally differentiated into macrophages - Cytokine-macrophage inhibitory factor (MIF) secreted by TH1 cells prevent macrophages from migrating beyond the DTH reaction site. - Lytic enzymes released by the macrophages cause erythema and blistering skin lesion formation as the Ag/self-protein complexes are destroyed.

IgE Receptor: 1) High affinity Fc∑R1

- Expressed in high levels on basophils and mast cells - This signaling leads to mast cell and basophil degranulation - CH3 domain of IgE interacts with alpha chain of Fc∑R1

What is negative selection? Do we have experimental proof of negative selection?

- Immature B cells that express auto-Ab against self-reactive Ag are eliminated in the bone marrow (clonal deletion) [Eliminate self-Ag] H2d/k transgenic mouse lacks IgM Ab specific for Hdk because B cell with anti-H2k binds to self-Ag Class I MHC so H2k is present on stromal cell of H2d/k transgenic mice and self-reactive B cell is eliminated Self-reactive B cells can be saved from apoptosis by heavy chain associating with different light chains (light chain editing)

What are the reactants of the Lectin Pathway?

- MBL complex recruits and activates MASP-1 & -2 -- MASP- 1 & -2 are serine proteases, which cleave C2 and C4 like C1s in classical path (= formation of C3 convertase) ** rest of pathway is like classical starting at C3 convertase

Celiac disease:

- Peptides naturally produced from gluten do not bind MHC class II molecules - An enzyme, tissue transglutaminase, modifies the peptides so they can now bind to the MCH Class I molecules - The bound peptide activates gluten-specific CD4 T cells - The activated T cells can kill mucosal epithelial cells by binding Fas, they also secrete IFN gamma, which activates the epithelial cells

Facts about localized type III (Arthus Rxn)

- Site of injections: used to desensitize IgE-mediated antigens (5-12 hours later) - Erythema and hard swelling (induration) of 50 mm or more w/ no well defined edges - Localized reaction induced by injection of an Ag in an individual w/ high levels of Ab for said Ag in circulation - Swelling and bleeding at site, peaks 4-10 hours after injection - Can occur after rapid type I to insect bite - May develop in lungs after inhalation

TCR signaling (steps)

- TCR clustered w/ CD3 and zeta chains - CD4/8 facilitate signaling through Lck (tyrosine kinase) - CD3 and zeta contain ITAMs, become involved in signalling - Lck phosphylates ITAMs to stimluate signaling along PLCgamma, Ras/Rac, and Pi-3-kinase pathways - NFAT, NFkB, and AP-1 are generated

Type IV process recap:

- Th turn into Th1 - Th1 secrete variety of cytokines after exposure to antigen, factors attract macrophages - Only 5% of cells are antigen specific Th1, the rest are macrophages and non-specific cells - Th1 cells release IL-3 and GM-CSF, induces hematopoiesis and granulocyte-monocyte lineage of cells - IFN-gamma and TNF-beta induce changes in nearby endothelial cells causing them to express adhesion molecules so leukocytes can migrate there - Monocytes are attracted to the site by monocyte chemotactic factor (MCP-1/CCL2) at 24-48 hours and become terminally differentiated into macrophages - Cytokine-macrophage inhibitory factor (MIF) secreted by Th1 cells prevent macrophages from migrating beyond the DTH reaction site

Common sources of allergens:

- inhaled include pollen, dander, mold, feces of dust mites - injected include insect venom, vaccines, drugs, proteins (peanuts) - ingested include food and oral drugs - contact material include plants, synthetic materials, metals

What do mast cells do?

- maintain integrity of tissue - alert immune system- (local trauma and infection) - facilitate repair of damaged tissues

CD4+ T-Helper Cells

-CD4+ and CD3+ -MHC class II restricted - assist phagocytes to kill intracellular pathogens (optimizes the innate immune response) - aid antigen-stimulated B cells to become plasma Cells. -Help T cells proliferate/differentiate to effector CTLs

discuss MHC and immune responsiveness 1) Determinant selection model

Determinant selection model - different Class II MHC molecules differ in ability to bind to processed antigens

Differentiation of Progenitors to Mature T cells in the Thymus

Development of thymocytes in the thymus proceeds via a series of sequential processes that ultimately lead to the generation and export of three distinct T cell lineages tolerant to self-antigens. These processes are contingent on progenitor-thymic epithelial cell interaction, the IL-7 cytokine, and various chemokines.

Tuberculin Skin Test (TST) steps:

-Mixture of antigens injected into arm -Measure reaction at 48-72 hours -Measure induration, not erythema -Record reaction in millimeters, not "negative" or "positive" -Detects cell-mediated immunity against M. tuberculosis -TST has its usefulness and also its limitations

Adaptive Immunity

Develops only after exposure to inducing agents such as microbes, abnormal body cells, toxins, or other foreign substances. Acquired defenses are highly specific and can distinguish one inducing agent from another. This recognition is achieved by white blood cells called lymphocytes (T cells and B cells) which produce two general types of immune responses.

Detection of Type I

-Skin tests using small amounts of potential allergens into the skin, stimulating local mast cell degranulation and histamines induce a localized wheal-and-flare inflammatory response usually within 30 minutes. -RIST and RAST tests

What is the thymus?

-T lymphocyte maturation occurs here -bi-lobed organ situated above the heart (primary lymphoid organ)

What are the steps involved in phagocytosis?

-bacterium becomes attached to phagocytes by evaginations due to pseudopodia surrounding the bacterial cell -bacterium is ingested due to pseudopodial engulfment thereby forming a phagosome -phagosome fuses with a lysosome, becoming a phagolysosome -lysosomal enzymes digest captured bacterium -digestion products are released from phagocytic cell

What is the anti-nuclear antibody (ANA) test used for? What testing methods may be used? Why is it useful?

-detection of anti-nuclear antibody in pt's sera. - test can be enzyme immunoassay or indirect IF -is useful as a diagnostic indicator, prognostic indicator or as a means to monitor the effectiveness of therapy

Ag-binding site of Ab

-located in variable region composed of 3 CDRs -T cell epitopes are often internal (hydrophobic) and are linear or continuous

5.4 (2) Discuss the functional and structural differences between the subclasses of Ig.

Different types vary in heavy chain constant region called isotpyes mu - IgM delta - IgD gamma - IgG epsilon - IgE alpha - IgA structure of IgG, IgD, IgA: 2 VL, 2 CL (light chains) 2 VH, 2 CH1, 2 CH2, 2 CH3 (heavy chains) hinge regions structure of IgM, IgE: no hinge region additional domain of CH4 (heavy chains)

What are the properties of inhaled allergens that may cause localized ana.?

-proteins, only they will induce T-cell response -allergens are often proteases -low dose: favors activation of IL-4-producing CD4 T cells - have low molecular weight= diffuse out of particle into mucus - high solubility: readily elude from particle - High stability: can survive in desiccated particle - Contain peptides that bind host MHC class II molecule: required for T-cell priming ** includes dust mite (Dermatophagoides pteronyssimus) - Major allergen in the feces of dust mite is cysteine protease Der p1 - Der p1 is homologous to the protease papain (from the papaya fruit) - Der p1 destroys intercellular junctions by cleaving occludin, a tight junction adhesion molecule, in airway epithelium - Der p1 also cleaves a subunit of the IL-2 receptor and interferes with the maintenance of TH1 cells leading to a TH2 cell bias - Occupational allergies occur - example: some individuals in the meat industry develop an occupational allergy to meat tenderizer - cause of allergy is the papain of papaya origin in the tenderizer

4 signs of inflammation

-redness (rubor) -swelling (tumor) -pain (dolor) -fever (calor) accompanied by acute phase response; vasodilation, increased permeability in local capillaries, migration of phagocytes

Plasma Cells

Differentiated B cells that reside in the medulla and secrete antibodies into circulation

Immunoglobulin G (IgG)

1) 75% of total circulating Igs 2) Circulates between blood and interstitial fluid and has a half life of 3 weeks 3) Can be transported across placenta and enter the fetal circulation (mother's immunity is transferred to fetus) 4) Plays a major role in elimination of microbes by facilitating opsonization by phagocytes, ADCC by NK cells, complement activation and neutralization of viruses and toxins (ADCC- antibody dependent cell mediated cytotoxicity)

MAC Mechanism

1) A pore of around 100A diameter 2) These pores are large enough to allow escape of small molecules and electrolytes down concentration gradients 3) The larger molecules remain within the target cell increasing the osmotic pressure 4) Water enters the cell by osmosis and the cell swells and ruptures (osmotic lysis)

Describe the role of the AIRE protein in mTECs. Explain why this contributes to central tolerance induction.

1) AIRE is a transcription regulator and its presence leads to the expression of tissue-restricted proteins in thymic epithelial cells (TECs), particularly medullary TECs. 2) The number of self-peptide/MHC complexes available for presentation on the surface of mTECs is greatly increased as a result of expression of the autoimmune regulator protein (AIRE) which is encoded by the AIRE gene.

Superantigens

1) Activates subsets of T Cells (mainly bacterial products which act in a nonantigen specific fashion on T cells) 2)Trigger multiple clone activation (2-20%) 3) They bind to the VB region of the TCR and they are not processed by the APC

Describe somatic recombination

1) Activation of recombinases, which are the nucleoprotein products of the RAG-1 and RAG-2 genes (recombination activating genes), triggers the somatic recombination process. 2) Combinational Diversity: combine V,D and J in any combination 3) Junctional Diversity: additional V, D or J gene segments are deleted or inserted via Tdt to maintain downstream open reading frame 4) Random association/assortment of any light chain with any heavy chain (increasing diversity) (constructed variable region and constant region genes are transcribed to hnRNA that is spliced to mRNA. mRNA is translated to a light chain and heavy chain expressing a variable and constant region)

Describe the classical pathway and include the mode of activation and steps leading to the binding of C1

1) Activation requires two adjacent molecules of bound IgG or a single molecule of IgM bound to the antigen via its Fab region 2) Antigen/antibody complex exposes the C1 binding site on the Fc region of the antigen which allows C1 to bind 3) C1 has three components, C1q, 2C1r and 2C1s and this forms a flower like appearance (IgM is more efficient at activating the compliment pathway because its a pentamer that has two adjacent Fc regions which is required for C1 activation)

Generation of memory B Cells

Differentiation of activated B cells to memory cells occurs in germinal centers, one week after antigenic challenge with a T dependent antigen. Because this event occurs within the same time frame as isotype switching and affinity maturation, memory B cells usually express high affinity immunoglobulin, and isotypes other than IgM.

List the molecules on a dendritic cell that are critical for antigen presentation leading to activation of CD4+T cells.

1) All APCs require Class II MHC molecules and co-stimulatory molecules (CD80/B7-1, CD86/B7-2 , and CD40). All of them also express FcγR (especially dendritic cells)) 2) APCs express these molecules in low levels all the time but interaction with antigen or cytokines increase their expression (Immature dendritic cells have a higher level of these cell surface molecules than macrophages and B cells and are the most effective APCs.)

Name the two major pathways of complement activation and the pathway to which both converge.

1) Alternative Pathway (triggered by microbial agents) 2) Classical Pathway (requires Igs) Both pathways converge at a pivotal point where C3 is converted to C3a and C3b followed by the common/terminal pathway

Describe the alternative pathway with respect to the role of C3-tickover.

1) An innate host defense that does not require Ig for activation neither C1, C2 or C4. It is activated following invasion by an infectious agent (dependent on C3b). 2) Tickover: C3b is derived from normal continuous low level break down. It is always circulating in blood 3) In the absence of microbes C3b is inactivated by complement regulatory proteins. But in the presence of microbes especially bacteria, C3b binds to the surface initiating alternative pathway.

Name one cell surface protein to identify all B cells, all T cells and subpopulation of T cells (helper versus cytotoxic).

1) Anti-CD19 antibodies with a fluorescent probe can be used to detect the B cell count in peripheral blood 2) Anti-CD4 antibody with a fluorescent probe can be used to detect the CD4+ T cell count in peripheral blood

Name the 4 soluble mediators of the immune system

1) Antibodies 2) Complement Proteins 3) Cytokines (small peptides) 4) Chemokines

Natural Tregs (nTregs)

1) Are produced in the thymus and are the dominant players in controlling self reactive T cells in the periphery that evaded central tolerance. 2) Tregs down regulate and suppress immune responses to self and/or foreign antigens in the periphery (peripheral tolerance). (These cells play a critical role in peripheral self tolerance and modulating adaptive immune response. When nTregs are depleted to enhance immune response to pathogens the immune response against self antigen cells is also enhanced - balance is key)

Define Autocrine, Paracrine and Endocrine

1) Autocrine: When the cell is affected by its own secretion 2) Paracrine: Cytokines released from the cell act on neighboring cells 3) Endocrine: Cytokines released enter the blood and act on cells further down

What are the principle cell types of adaptive immunity?

1) B Cells (plasma cells) 2) T Cells (CD4+ & CD8+) 3)CD4+ Subsets: Thp, Th0, Th1, Th2, Th17, nTreg, a/iTreg

B Cells

1) B cell receptor for antigen is the mIg (highly specific) 2) B cell acts as APC for T dependent antigens (most antigens) 3)The receptor and antigen are internalised in endosomal vesicle. Processing of the material involves its breakdown after fusion with lysosome. The receptors are then recycled to the surface and foreign particles are presented to MHC Class II

Describe the differentiation of basophils and mast cells from a myeloid precursor. What is the source of IL-3?

1) Basophils and mast cells both arise from myeloid progenitors in the bone marrow. 2) Differentiation from the progenitor to a mature basophil occurs in the bone marrow in the presence of IL-3 (which is secreted by activated T cells) (mast cells leave bone marrow as immature cells which migrate into peripheral tissues)

List the names of macrophages as function of tissue

1) Bone Marrow: Monoblasts 2) CNS: Microglia Cells 3) Liver: Kupffer Cells 4) Synovium: Synoviocytes 5) Lung: Alveolar Macrophages 6) Lymph & Spleen: Macrophages

Classical Pathway Generation of Convertases

1) C1 cleaves C4 into C4a and C4b. C4a (anaphylatoxin) triggers inflammation via mast cell and basophil granulation. C4b is deposited onto microbial surface 2) C1 then cleaves C2 into C2a and C2b. C2a attaches to antigen bound C4b producing C4b2a the Classical C3 Convertase 3) C3 convertase (C4b2a) then cleaves C3 to C3a and C3b. Both of these products play important roles in host defense. C3a is an anaphylatoxin and C3b attaches to the C3 convertase to produce C4b2a3b the C5 convertase

Regulatory Proteins that are unique to the classical pathway

1) C1 esterase inhibitor (C1INH): Forms a complex with C1 preventing activation of classical pathway. It also inactivates kallikrein (which links compliment and Intrinsic coagulation pathway) C4 binding protein (C4bp): Cofactor for Factor I and binds to fluid phase C4b preventing its attachment to cells. When Classical C3 convertase forms, C4pb competitively binds with C4b displacing C2a.

What happens after C5 convertase is formed in the classical pathway?

1) C5 Convertase (C4b2a3b) cleaves C5 into C5a and C5b. C5a is an anaphylatoxin leading to mast cell and basophil degranulation. C5a is also a chemotactic for phagocytes. 2) C5b attaches C6 and C7 which attaches to target cell membrane. C8 and multiple C9 molecules attach forming the membrane attack complex (MAC) (Insertion of the MAC into the target cell membrane induces osmotic lysis and death of the microbe)

Explain the consequences of CD200R interaction with CD200

1) CD200 is a membrane bound protein present on a range of cells including T cells, B Cells and Dendritic Cells. It is not linked to any signalling cascade. 2)CD200R is mainly expressed on myeloid cells (monocytes, macrophages and dendritic cells) and also on some T cells (more on CD4+ than CD8+ CD200R expression is up-regulated on both CD4+ and CD8+ T cells after stimulation. CD200R IS LINKED TO A SIGNALLING CASCADE. Interaction of CD200 and CD2ooR leads to inhibition of cell possessing the receptor. (CD200 expression on tumor cells acts to suppress anti tumor immune response)

Specify the components of the B cell receptor complex.

1) CD79a/CD79b heterodimer 2) BCR = two identical light chains and heavy chains, variable and constant region (B Cell antigen recognizing receptor) (heterodimers CD79a/CD79b couple the BCR to intracellular signaling cascades)

CR3a/4aR and C5aR

1) CR3a/4aR binds complement fragments C3a and C4a while C5aR binds complement fragment C5a. 2) Ligands C3a, C4a and C5a are released following the activation of the classical pathway of complement while Ligands C3a and C5a are released following activation of the alternative pathway. (C3a, C4a and C5a are anaphylatoxins)

Beneficial effects of fluid exudate (vascular permeability)

Dilution of toxins, entry of abs to allow for lysis of microorganisms and opsinization and toxin neutralization. Fribrin formation. Delivery of nutrients and O2. Drainage of fluid exudate and antigens into lymphnodes for stimulation of immune response (if needed)

Explain the difference in the following nomenclature of the following: MHC Class II, HLA Class II & H2. (Specify the human and the murine MHC-class II molecules)

1) Class II MHC (major histocompatibility complex): any species 2) HLA-Class II: Human Leukocyte Antigen - humans - chromosome 6 3) H2-Mouse: Hstocompatibility-2 mouse (H2-IA, H2-IE) -chromosome 17 4) K, D & L Class I MHC molecules in mice are the equivalent of B, C & A Class I MHC molecules in man 4) DP, DQ & DR Class II MHC molecules are the equivalents of H-2M, I-A & I-E in mice (within the class II regions of both systems are areas which encode molecules involved in antigen processing: Proteosome and TAP 1 & TAP 2)

HLA-Class II Molecule (Class II MHC)

1) Class II MHC antigen presenting cells are only expressed on Macrophages, dendritic cells and B cells. 2) MHC genes are found on chromosome 6 and are called HLA (human leukocyte antigens)

Specify the components of the classical pathway, the alternative pathway and the common/terminal pathway

1) Classical Pathway: C1, C2, C3, C4, C5 2) Alternative Pathway: C3b, Factor B, Factor D, Properdin, C3 and C5 3) Common/Terminal Pathway: C5b, C6, C7, C8 and C9

Explain the role of FcεRII (CD23) & IgE antibodies, Major Basic Protein; Eosinophil Cationic Protein in host defense against helminths

1) Eosinophils play a major role in immunity to parasites especially helminths which are resistant to neutrophil and macrophage destruction. 2) Their role in defense against these helminths require IgE antibodies generated in adaptive immunity following B cell activation. 3) Eosinophils indirectly recognize helminths via their low affinity FcεRII (CD23) receptor which binds to IgE antibodies on the helminths. This interaction triggers degranulation of eosinophils leading to the release of major basic protein (MBP) and eosinophil cationic protein (ECP) which are very toxic to helminths.

Three terms that are used to refer to the component of the antigen with which receptors of the immune cells recognize and interact

1) Epitope 2) Antigenic Determinant 3) Determinant

Immunoglobulin M (IgM)

1) Exists as a monomer when membrane associated but its secreted from plasma cells in a pentameric form 2) Consists of 5 covalently attached monomeric units and a single short J chain to facilitate polymerization of the monomers. 3) 15% of total Ig and is largely intravascular. Only Ig expressed on immature B cells and expressed on naive B cells with IgD 4) Half life of 5-7 days. Ten antigen binding sites but steric hindrance impedes simultaneous occupation of all sites. (high avidity) 5) Activates the classical pathway of complement which requires only one IgM antigen complex (leads to enhanced phagocytosis and lysis of bacteria)

Immunoglobulin D (IgD)

1) Exists only as a membrane bound form and expressed on naive B Cells with IgM. 2) Low detectable serum levels of IgD likely reflect products of B cell death.

What are the four defining characteristics of adaptive immunity?

1) Exquisite Specificity: pre-existing array of cells with a unique receptor (the pool of cells cover immunity to all conceivable antigens) 2) Lag Time (First encounter) 3) Memory: Memory cells form after initial contact and respond more quickly if the same antigen is presented a second time 4) Adaptivity (Recruitment of cells during adaptive immune responses and their activation depends on the action of cytokines generated during innate immunity.)

Direct Coombs test vs Indirect Coombs test

Direct Coombs Test is used to demonstrate in vivo coating of red blood cells with IgG antibodies Indirect Coombs Test demonstrates in vitro reactions between red blood cells & antibodies in a patient's serum sample.

List The Steps For Exogenous Antigen Processing and Presenting by MHC II

1) Extracellular microbes penetrate host's physical defense and are endocytosed by APCs 2) Fusion of endocytotic vesicle with lysosomes that release their content into endosome 3) Newly formed vesicle fuses with endosome that contains MHC II creating chimeric endosome 4) MHC II/Ii complex is exposed to lysosomal enzymes and Ii chain is degraded allowing antigenic peptide to bind to MHC II groove. 5) Chimeric endosome migrates to and fuses with cell membrane and antigen peptide/MHC II is displayed on surface of APC. 6) T Cell receptors on CD4+ cells recognize this and the T cell is activated and secretes cytokines

List opsonin and the receptors on the phagocyte that it interacts with

1) Fcγ :Fcγ Receptor 2) CRP: CRP-Binding Site 3) C3b:CR1 (Complement receptor-1) (Clinical chemistry labs monitor CRP levels in the blood to indicate inflammation)

CD8+ pCTL Activation

1) First pCTL forms a conjugate with presented endogenous peptides on class I MHC (numerous molecular interactions occur -TCR/MHC I complex and CD8/MHC I at the a3 domain). Followed by expression of IL-2R 2) Activation of Th1 cells and secretion of IL-2 and IFNy 3) Th1 cytokines act on pCTL and it detaches from MHC I complex and differentiates into mature CTL (7 days). Clonal expansion of pCTLs which express IL-2R also occurs 4) Mature CTL then binds to target cells releasing perforins and Granzymse B (lethal hit) and apoptosis of cell occurs. CTL then looks for another target (pCTL needs to mature into CTL to kill cells)

Name three cytokines whose interaction with target cells leads to up regulation of Class I MHC

1) Following exposure to either cytokines IFNγ (type 2 interferons) 2) Following exposure to cytokine IFNa (type 1 interferons) 3) Following exposure to cytokine IFNB (type 1 interferons) (CD4+ Th1 cells secrete IFNγ where as IFNa is released from virally infected leukocytes and IFNB is released from fibroblasts)

Describe the role of GM-CSF, M-CSF and G-CSF in hematopoiesis (cytokines secreted by monocytes)

1) GM-CSF (Granulocyte Monocyte Colony Stimulating Factor): Differentiation of a myeloid progenitor to a GM progenitor and also enhances dendritic cell maturation, proliferation and migration. 2) M-CSF (Monocyte Colony Stimulating Factor): Differentiation of a GM progenitor to a monocyte 3) G-CSF (Granulocyte Colony Stimulating Factor): Differentiation of a GM-progenitor to a granulocyte (neutrophil) - can be employed in chemotherapy during bone marrow supression to boost WBC production

Structure of Class II MHC Molecule

1) Heterodimer consisting of two transmembrane polymoprhic polypeptide chains (alpha chain and beta chain both encoded by MHC). 2) Three isotypes: DP, DQ & DR that bind antigenic fragments between 15-30 AAs (accommodates larger antigens) -peptide binding cleft is between the two chains 3) Invariant Chain (Ii) associates with this molecule in the ER forming a trimeric complex (Class II MHC, Heterodimer & Ii) which blocks binding of endogenous peptides and directs transport of MHC II through the golgi where they are released with endosomes.

Structure of Class I MHC Molecule

1) Heterodimer made up of an alpha chain and a beta two microglobulin chain (not encoded by MHC/ non polypmorphic) 2) 3 domains: The a chain and peptide binding cleft between a1 & a2). 3) Peptide binding region is closed at both ends and can only bind peptides between 8-10 AA 4) CD8+ interacts with alpha 3 domain of MHC I (beta 2 microglobulin chain does not bind antigens but it is important because the heavy chain does not fold properly without it. Deficiency can lead to disease due to increased susceptibility to intracellular viral pathogens)

We distinguish between two IF methods depending on whether the fluorophore is conjugated to the primary or the secondary antibody:

Direct IF: uses a single antibody directed against the target of interest. The primary antibody is directly conjugated to a fluorophore. Indirect IF: uses two antibodies. The primary antibody is unconjugated and a fluorophore-conjugated secondary antibody directed against the primary antibody is used for detection. *more sensitive than Direct IF Application: easily identify and differentiate between the antibodies and antigens present in a tissue sample

Describe two roles of histamine in inflammation.

1) Histamine binds to vascular endothelium and leads to a translocation of P-selectin to the endothelial cell surface (important in rolling adhesion) 2) Histamine increases vascular permeability 3) Bronchoconstriction

Specify three names for sites within the variable region that bind the epitope (FAB)

1) Hpervariable Regions 2) Complementary Determining Regions (CDRs) 3) Paratope

Role of cytokines IFNγ, TNF, IL-4, IL-10 and TGFβ on macrophage activation and regulation of Inducible Nitric Oxide Synthase (iNOS)

1) IFNγ & TNF: Secreted by NK cells and TH1 cells (mainly), induces iNOS and enhances NADPH oxidase activity 2) IL-4, IL-10 and TGFβ: are products of Th2 cells and macrophages and down regulate the synthesis of iNOS. TGFβ is the most effective inhibitor of NO synthesis. (IL-4 is also secreted by mast cells and basophils upon degranulation)

Name the 5 antibody isotypes (Determined by constant Heavy Chain Region)

1) IgG: γ heavy chain 2) IgA: α heavy chain 3) IgM: µ heavy chain 4) IgE: ε heavy chain 5) IgD: δ heavy chain (Antibodies are expressed on the cell surface of B cells and when these cells are stimulated by antigens they differentiate into antibody secreting plasma cells.)

List the enzymes secreted by phagolysosomes (Mechanism I)

1) Lactoferrin: Binds to iron removing an essential ingredient for microbial metabolism 2) Lysozyme: Destroys muramic acid in bacterial cell walls - lysis 3) Defensins: Acts as a broad spectrum antibiotics against bacteria and fungi by permeabilizing their membranes 4) Myeloperoxidase Activity: Catalyzes hypochlorite formation

1) Name two tests that could be used as confirmatory tests if the CH50 shows a deficiency in overall complement. 2) How many CH50 units are required for a normal functional activity of Total Classical Complement?

1) Latex agglutination assays or ELISA can be used as confirmatory test for individual components deficiencies 2) 101-300 CH50 units are required for a normal functional activity of total classical compliment

Describe at least 6 ways in which T cell activation is down regulated.

1) Loss of T cell stimulation because infectious agent has been eliminated (MHC/peptide complex is no longer being presented to T cells) 2) Reciprocal regulation of cytokine secretion by Th1 and Th2 cells 3) CTLA-4/CD152 4) CD200:CD200R interaction 5) Apoptosis 6) PD-1: PD-L1/PD-L2 and regulatory T cells (nTregs and iTregs)

Migration of naïve lymphocytes from the blood into the lymph node

1) Lymphocytes leave their maturation sites via the blood, and either seed the secondary lymphoid tissues, or recirculate in immunosurveillance. 2) Migration of naive lymphocytes from the blood into lymph nodes occurs at specialized post capillary venules, termed high endothelial venules (HEV) -express molecules that bind circulating lymphocytes. (L-selectin)

List the mechanisms that phagocytes use to destroy ingested pathogens

1) Lysosomal Enzymes 2) Reactive oxygen intermediates (ROIs) 3) Hypochlorite 4) Reactive nitrogen intermediates (NO)

Macrophages

1) Mainly involved in antigen presentation associated with secondary immune responses 2) Generally occur at sites of infection where as primary responses occur in the secondary lymphoid tissue.

Immunoglobulin A (IgA)

1) May exist as a monomer, dimer or trimer and has a half life of one week. 2) Subtyped as IgA1 and IgA2. Dimeric and trimeric forms are associated with a J chain. 3) IgA is found in MALT and small traces in circulation. Found in GIT and secretions (tears, sweat, saliva etc) 4) Found at all external surfaces except skin impeding microbial binding to epithelia. Major antibody of milk and colostrum and infants who breast feed have mother's immunity to GIT pathogens

What are the limitations of using monoclonal antibodies as therapeutic agents?

1) Mice are often used for immunization to produce the monoclonal antibodies, and the human recipient of those antibodies often mounts an immune response that destroys these foreign antibodies (HAMA). One way to overcome this is by making human chimeric antibodies 2) The use of humanized antibodies has eliminated the problems associated with the HAMA response to the constant region of the antibody, but generation of anti-idiotypic antibodies (directed against the mouse variable region domains) continues to be a problem. 3) The size of the antibody molecule is a limiting factor for therapies requiring that the antibody leaves the circulation to enter tissue sites, if there is no co-existing inflammation. 4) The formation of immunoconjugates (antibody plus drug or radioactive molecule) requires a stable linkage to prevent the deposition of free drug or radioisotope into healthy tissues 5) Treatment of cancers with immunoconjugates is limited by the general lack of tissue specific antigens on most cancer cells.

Steps For Endogenous Antigen Processing and Presentation by MHC I Proteins

1) Microorganisms in the cytoplasm not enclosed within a vacuole are susceptible to the proteolytic action of the proteosome 2) Cytosolic proteins are targeted for degradation via ubiquitin attachment 3) Protein fragments from proteosome then bind to the transporter of antigen processing (TAP) proteins and are transported to the ER where they contact MHC I (B2 Microglobulin) 4) Complex is released from golgi into vesicles that fuse with cell membrane displaying the antigen peptide/MHC Class I (IFNγ enhances the expression of MHC I and is secreted by NK cells and Th1 cells)

Monocyte

1) Monocytes are a type of white blood cell that is a part of the innate system derived from progenitor cells during hematopoiesis 2) They are precursors of macrophages and dendritic cells and are weak phagocytes 4) Activated monocytes secrete cytokines: GM-CSF, M-CSF, G-CSF

What are the three phagocytes?

1) Monocytes: Limited phagocyte ability 2) Macrophages: specialized phagocytes 3) Neutrophils

Immunoglobulin E (IgE)

1) Monomeric antibody barely detectable in serum because most IgE is bound to FceR on mast cells and basophils 2) Multivalent antigen binding to IgE bound to mast cells and basophils lead to crosslinking of FceRs causing mast cell and basophil degranulation (release of histamine and IL-4 and IL-5) (Eosinophils also express FceRs which bind to IgE helminth complexes)

Describe the factors that contribute to diversity in the T cell repertoire

1) Multiple copies of germline V, D and J gene segments 2) Random selection and combination of V, D and J gene segments 3) Junctional diversity generated by the addition or deletion of bases 4) Random assortment of TCRa and TCRB chains. (junctional diversity is created when DNA nucleotides are deleted or inserted at V, D and J gene segment junctions in order to maintain (downstream) open reading frame)

Specify the three lineages of T cells that survive the selection processes in the thymus.

1) Natural Tregs (nTregs), [CD4+, CD25+, FOXP3+] 2) CD4+ Thp Cells 3) CD8+ pCTL Cells

Phagocyte Recruitment into Infected Tissues (Part 1)

1) Neutrophils and circulating monocytes are drawn into site of infection (via C3a & C5a) after bacteria activates complement system. 2) Initial stage is margination following vasodilation due to histamine release 3) Laminar flow of blood cell is disturbed causing turbulent flow and endothelial cell surfaces are activated locally 4) Adhesion molecules produce interaction between phagocytes and endothelial surface

List 5 examples of DAMPs that trigger inflammatory responses (activators of inflammasome)

1) Numerous molecules released during trauma or cell death 2) Reactive oxygen species and UVA irradiation (sunburn) 3) ATP and cholesterol crystals 4)Free Fatty Acids and other endogenous molecules 5)Silica Dust and urate crystals 6) Elevated extracellular glucose

Name three conditions in which Class I MHC decreases on target cell

1) On virally infected cells which decrease the number of Class I MHC self peptides expression on their surface. 2) Stress 3) Tumors also down regulate Class I MHC expression on surface of target cells.

Define Opsonization, ADCC, Complement Activation and Neutralization via IgG

1) Opsonization: phagocytosis that is triggered following binding of the Fc region of antibodies, bound by the pathogen, to FcγR on phagocytes. 2) ADCC: Process by which natural killer cells interact with, and destroy, target cells coated with antigen specific IgG. Natural killer cells express a low affinity FcγR whose interaction with target cell-bound IgG triggers the release of molecules cytotoxic to target cell . 3) Complement Activation: Requires two adjacent IgGs to be bound together 4) Neutralization of viruses or toxins results when IgG antibody binds antigen to inhibit the antigen's ability to bind to a cell surface receptor.

Name three other disorders in which there is an increase in circulating eosinophils.

1) Patients with allergic asthma 2) Patients with allergic dermatitis 3) Food allergies and other conditions in which allergy is the underlying cause. (Some people produce IgE against pollen and other allergens resulting in eosinophilia)

List the two main roles of macrophages

1) Phagocytes that reside in every tissue of the body 2) Activated macrophages function as antigen presenting cells for CD4+ T cells and they also secrete cytokines and chemokines which regulate and control inflammation and adaptive immunity (Recognition of microbes is direct via PRR Receptors & Ligand PAMPS or indirect via opsonins)

What are the principle cell types of innate immunity?

1) Phagocytes: Macrophages & Neutrophils 2) Natural Killer Cells (NKs) 3) Dendritic Cells 4)Accessory Cells: Mast Cells, Basophils 5)Eosinophils 6) Complement System

NADPH Oxidase and its role in phagocytosis (Mechanism II-ROI)

1) Phagocytosis triggers the assembly of NADPH oxidase complex on the membrane of the phagosome (some components of the complex are on the x chromosome and others are autosomally inherited) 3) NADPH oxidase uses oxygen in the presence of cytosolic NADPH (from PPP Pathway) - respiratory burst to generate a range of ROIs (Interferon Gamma (IFNγ): secreted by NKs and TNF secreted by macrophages and Th1 cells enhance NADPH oxidase activity)

TGFβ (Cytokine Secreted by Macrophages)

1) Plays a critical role in differentiation of Thp to a/iTregs (suppressor cells that tone down immune responses) 2) In the presence of IL-1/IL-6 and IL-23 plays a role in the differentiation of Thp to Th17 cells 3) Down regulates iNOS in phagocytes which decreases the production of NO

IL-1 (Cytokine Secreted by Macrophages)

1) Plays a role in differentiation of monocytes to macrophages 2) Critical role in inflammation especially with TNF 3) In the presence of IL-23 and TGFβ, plays a role in the differentiation of Thp to Th17 cells

IL-1 and TNF Combined (Cytokine Secreted by Macrophages)

1) Plays a role in lowering blood pressure leading to shock. 2) Enhances secretion of cytokines and chemokines by macrophages 3) Plays a role in inflammation by inducing vascular enothelium to secrete IL-8 (CXCL8) and MCP-1 (CCL2) 4) Induces de novo expression of VCAM-1, ICAM-1 and E-selectin and upregulates expression of ICAM-2 on vascular endothelium 5) Induction of fever via hypothalamus

Describe the steps in phagocytosis

1) Recognition and binding of pathogen 2) Ingestion of pathogen forming a phagocytic vacuole called a phagosome 3) Lysosome fuses with phagosome to form phagolysosomes 4) Lysosomal contents is released (armamentarium) 5) NADH oxidase and iNOS activation

Fate of autoreactive T cells in the peripheral circulation

1) Signal 1 w/out signal 2 = anergy 2) if inibitory receptors (CTLA-4 and/or PD-1) engage B7 on APCs, become anergic...these receptors have higher affinity to B7 than CD28; low number of B7 on APCs (aka not activated) means less CD28 are binding B7) 3) suppression by Treg (which secfrete IL-10, TGFbeta)

NK cells express activating and inhibitory receptors that interact DIRECTLY with ligands on the target cell. Name three classes of the ligands for these receptors.

1) Specific self Class I MHC 2) MHC Class I like molecules 3) Molecules unrelated to MHC

List the Armamentarium (ROIs) produced by NADPH oxidase activation

1) Superoxide Anion 2) Hydrogen Peroxide 3) Hydroxyl Radical 4) Hydroxyl Ion 5) Hypochlorite (catalyzed by myeloperoxidase) (Powerful killing mechanisms)

List 4 things that nTregs suppress

1) Suppress the transcription of a number of genes including IL-2 gene (T cell growth factor) 2) Suppress the proliferation of effector CD4+ and CD8+ cells 3) Suppress antibody production by B-Cells 4) B-Cell proliferation

Thp cells differentiate to an intermediate cell, Th0, which secretes three cytokines. Specify these. Specify one that contributes to polarization of the Th0 to (a) Th1 cell, (b) Th2 cell

1) ThO secretes IL-4, IL-2 and IFNy 2) If IL-4 predominates the microenvironment then the ThO will polarize to a TH2 subset 3) If IFNy predominates the microenvironment then the ThO will polarize to a Th1 subset (activated mast cells are the source of IL-4 while NK cells are the source of IFNy)

Two major types of PPRs

1) Toll-like receptors (TLRs)- transmembrane receptors 2) NLR family (intracellular/cytosolic receptors) - Include NALP/NLRP family of proteins that play a key role in inflammation. The most widely studied one is the NALP3 protein

Name the cytokine that is released when NK cells are stimulated with IL-12? Explain the role of IL-15, and IL-18 when NK cells are stimulated with IL-12 and Explain how lymphokine activated killer cells (LAK cells) are generated and describe their unique property.

1) When NK cells are stimulated with IL-12, the cytokine IFNγ is released. 2) Both IL-18 and IL-15 enhance the secretion of IFNγ by IL-12 3) In the presence of high concentrations of IL-2 NK cells differentiate into lymphokine activated killer cells (LAK cells) that are potent killers of tumor cells (occurs in vitro -lab)

Cycle of virus replication

1) attachment of the virus 2) penetration of host cell 3) uncoating of viral particle 4) TX of viral genome 5) viral protein synthesis 6) replication of viral genome 7) capsid assembly from protein subunits 8) packaging of viral nucleic acids into capsids 9) release of viral particles from the cell

IL-6 (Cytokine Secreted by Macrophages)

1) binds to cognate receptors on liver cells which lead to the secretion of C-Reactive Protein (CRP) 2) In mouse IL-6 in the presence of TGFβ play a role in the differentiation of the Thp to Th17 cells.

Three stages of Th17 generation

1) differentiation: involves TGFB + IL-6/IL-1 +TGFB 2) amplification: involves IL-21 autocrine amplification 3) stabilization: involves IL-23 from activated APCs (Th17 releases IL-21 which amplifies its affects by acting as a growth factor and also releases proinflammatory cytokines IL-17A,F, IL-22)

What are the three main reasons that cytokines do not exert actions non-specifically?

1) expression of specific receptors by target cells 2) localized effective concentration 3) short half-life of the cytokine (~several days)

What does extravasation of naive lymphocytes into tissues at HEV require?

1) interaction of L-selectin on lymphocytes with its ligand on endothelial cells to induce lymphocyte rolling (GlyCAM-1) 2) activation of integrins (LFA-1) on the lymphocytes, increasing their adhesiveness and allowing stable binding to HEV 3) lymphocyte secretion of matrix metalloproteinases that proteolytically degrade collagen to generate channels in the subendothelial basement membrane 4) Transendothelial migration of lymphocytes into the tissue. (If naïve lymphocytes do not encounter antigen in the lymph nodes, they continue their immunosurveillance in the lymphatics. One cycle through the body takes approximately one to two days.)

Describe the molecular interactions between the dendritic cell and T cell that leads to T cell activation.

1) interaction of peptide/MHC class II with TCR 2) Interaction of MHC Class II with CD4 3) Interaction of B7-1/CD80 and B7-2/CD86 costimulatory molecules on dendrite with their counter ligand (CD28/CTLA4) on CD4 cell 4) Interaction of CD40 on dendrite with its counter ligand CD40L/CD154 on CD4+ (enhances T cell response) 5) Interaction of LFA-3 on dendritic cell with CD2 on CD4+ cell (adhesion) 6) Interaction of ICAM-1 & ICAM-2 on dendritic cell with LFA-1 on CD4 cell (adhesion) -molecular interactions occurring during conjugate formation enhance the avidity of peptide/MHC interactions with the TCR

Specify the molecules that comprise a T cell Receptor complex (TCR).

1) two transmembrane polypeptide chains classified as either alpha or beta. Each chain has a variable and constant region Each heterodimeric TCR is expressed on the cell surface in association with 5 invarient polypeptides termed CD3. (CD3 links the antigen binding receptor of the T cell with signaling pathways)

DTH is unique in that it takes ___ weeks for sensitization to occur and then ____ hours for the effector phase to peak after secondary contact.

1-2 weeks 48-72 hours

4 components of innate immunity

1. Anatomic 2. Physiologic 3. Phagocytic and endocytic 4. Inflammatory

Five mechanisms of antibody diversity

1. Availability of multiple V gene segments 2. Combinatorial diversity (different VDJ and VJ combination) 3. Assortment of heavy and light chains. 4. Junctional and insertional diversity results because VDJ or VJ recombination sites are not precise so recombination of some basepairs will change amino acid sequences, known as *N-region diversification*, which is mediated by *deoxynucleotidyl-transferase*. 5. Somatic hypermutation- point mutations can occur in the V regions AFTER Antigenic stimulation of the B cells. Results in affinity maturation, the selection of mutants that have higher affinity for the antigen in subsequent (secondary) responses to antigen.

4 Facts about Neutrophils

1. Do not function as antigen presenting cells 2. Do not secrete cytokines or chemokines 3. Recognition (direct and indirect) is the same as that described for macrophages. 3. Armamentarium products and functions are the same as that described for macrophage

Thymic Cortex Processes

1. Entry of bone marrow derived lymphoid progenitors at thymus cortico-medullary junction and CD2 expression 2. Expression of a preTCR complex (Rearranged beta chain, CD3, and CD2 3. Expression of rearranged beta chain, both CD4 and CD8, + PreTCR complex, CD2 and CD3 (DP thymocyte) 4. Expression of rearranged alpha chain, a TCR complex + CD3, CD4, CD8 and CD2 (positive and negative selection occurs here) 5. Selection of DP thymocytes to SP that express TCRs useful to the immune system. ( Lineage determination) 6. Remaining cells enter medulla and negative selection process continues 7.. Mature naive CD4+ (Thp) and CD8+ (pCTL) cells migrate to peripheral lymphoid tissues (DP = double positive CD4 and CD8)

Thymic Medulla Processes

1. Expression of the AIRE gene in mTEC to allow expression of tissue proteins in the thymic medulla (for cell surface display with MHC). AIRE protein is a transcription regulator. 2. Interaction of SP thymocytes with mTECs to select autoreactive cells. Interactive avidity differs from that in thymic cortex (includes CD8 or CD4 interaction with MHC class I or class II on thymic epithelial cells; tissue-restricted proteins/MHC complexes are displayed on mTECs). 3. Negative selection -destruction of autoreactive cells 4. Export of three lineages of T cells ( nTreg (CD4+, CD25+ & FOXP3+), CD4+ Thp, and CD8+ pCTL). (SP = single positive CD4 or CD8 cells)

Factors influencing immunogenicity

1. Foreignness-self from nonself 2. Molecular size->100kD 3. Chemical composition/complexity-proteins are best, polysaccharides are next, lipids/nuc acids suck 4. Susceptibility/degradability-must be easily degraded and processed

Categories of immunodeficiency

1. Neutrophil disorders 2. Antibody deficiency 3. Complement Deficiency 4. T-cell dysfunction

Ab effector functions

1. Opsonization 2. Complement activation-IgM and IgG 3. Ab-dependent cell-mediated cytotoxicity (ADCC)-Ig bound to targets recognized by NK cells through FcR molecules 4. Transcytosis-IgA can pass through epithelial layers (maternal IgG to fetus=passive immunization)

CTL Mechanisms of Target Cell Killing

1. Perforins- perforates holes within the target cell membrane to result in tonicity-based lysis. 2. Granzymes- eliminates viral lifecycle by killing the host cell. 3. *CD95/95L (Fas/FasL)- activation of apaotosis*

Steps of phagocytosis

1. Phagocyte attaches bacteria by evaginations 2. Bacterium ingested forming phagosome 3. Phagosome fuses with lysosome = phagolysosome 4. Lysosomal enzymes digest bacterium

What does the adaptive response result in?

1. cells whose function is to eliminate the pathogen 2. longer-lived primed memory cells that await second exposure

Generation of Ab diversity

1. multiple V, D, and J segs exist 2. combinatorial VJ and VDJ joining 3. junctional flexibility 4. P-addition 5. N-addition (by TdT)-only in heavy rearrangement 6. somatic hypermutation (Ag-dependent) 7. association of heavy and light chains

cytosolic pathway

1. protein degraded into peptides (endogenous) 2. peptide transported from cytosol to RER lumen 3. Class I MHC assembled and bound to peptide Ag w/ help of chaperones 4. transported outside RER by TAP doorways 5. packaging at Golgi

endocytic pathway

1. protein engulfed and degraded in endosome 2. invariant chain carries Class II MHC to endosome 3. invariant chain degraded to CLIP 4. CLIP exchanged for exogenous Ag by HLA-DM 5. transports to cell surface

steps of recombination

1. recognize RSS and bring two signal sequences together 2. cleave (RAG-1/2) one DNA strand at juncture of RSS and coding region 3. cleave (RAG-1/2) second DNA strand and form hairpin at cut end of coding sequence 4. random cutting of hairpin to make sites for P-nucleotides (palindromic sequence) 5. optional addition of <15 N-nucleotides by TdT 6. repair/ligation of coding and signal sequences by double-stranded break repair

What are the four major parts of class switching?

1. switch region 2. switch recombnase 3. cytokine signaling 4. activation-induced cytidine deaminase

papain digestion of IgG

2 Fab and 1 Fc; cleaves at hinge region above disulfide bonds

Antibody Light Chains

2 types: Each chain has a variable and a constant region. Kappa: 60% of human light chains Lambda: 40% of human light chains

What are some tests for cell-associated antigens?

Direct immunofluorescence Indirect immunofluorescence Fluorescent-Activated cell Sorting (FACS)

What are lymphoid cells?

20-40% of all cells circulating blood, lymph, and lymphoid organs including T lymphocytes, B lymphocytes, NK cells

Adaptive immune response

2nd line of defense mediated by APCs and lymphocytes; relies on gene rearrangement & clonal expansion characterized by specificity, diversity (multiply), memory, and self/non-self recognition humoral or cellular

Complement

30 serum proteins involved in innate defenses, works with adaptive system; circulate as zymogens; classical, alternative, or lectin pathway 1. Lysis of cells, bacteria, viruses 2. Opsonization (inc. phagocytosis)-PRRs recognize additional complement byproducts 3. Binding to complement receptors triggers functions as inflammation & regulatory molecule secretion 4. Removal of immune complexes from circulation and deposits from spleen/liver

Structure of MHC Class I molecule

45 kDa alpha-chain associated with 12 kDa beta-2-microglobulin fully folded conformation of beta-2-microglobulin is the only form that can be expressed on the surface of the cell beta-2-microglobulin, alpha-chain, peptide (absence of any of these means no expression on cell surface) alpha chain: -alpha-1, alpha-2, and alpha-3 domains (each with 95 aa) -these are external domains -alpha-1 and alpha-2 function in the formation of the peptide-binding cleft where peptide of 8-10 aa binds to cleft -alpha-3 is highly conserved and interacts with CD8 molecules present on the Tc cells peptide-binding region is made of eight anti-parallel beta-strands spanned by two long anti-parallel alpha-helical regions transmembrane domain - 25 aa cytoplasmic tail - 30 aa

Antibody Heavy Chains

5 classes of heavy chains and correspond to class name of IgG, A, M, E, D. Each chain has a variable and a constant region

List the 5 CD3 membrane complexes

5 invariant chains: γ, ε, δ, ζ, and η; (γ, ε, δ are in Ig superfamily, ζ and η are not) Heterodimers: γε, δε, and ζη Homodimer: ζζ

Phagocyte Recruitment into infected Tissues (Part 2)

5) Initial interactions between phagocytes (neutrophils) and the endothelial surface are weak and serves to slow the cells down (rolling adhesion) 6) Subsequent interactions are strong leading to firm adhesion. 7) Neutrophils are then able to recognize the junction of endothelial cells and move between them (diapedesis) 8)Enzymes released at the leading edges digest elements of the basement membrane allowing extravasation of neutrophils which flow down a chemical gradient to site of infection. 9)Phagocytosis, degranulation and O2 production occurs

Newborn hemolytic anemia

65% of newborns have complication due to hemolytic anemia If mom has O type blood and baby has blood in the A or B group, each subsequent pregnancy = develop IgG antibody that crosses placenta and reacts with fetal blood group antigen. - clinical manifestations are elevated bilirubin and jaundice -- expose baby to low level of UV to break down bilirubin. Blood transfusions may be needed in severe cases.

Name three categories into which agglutination is categorized and state the difference between direct agglutination and passive agglutination?

Direct, passive, or reverse passive agglutination Direct agglutination is a test used to to detect antibodies in the patient's serum by incubating the patient's serum with particles (e.g. bacterium, red blood cell) that naturally express particular antigens (e.g. ABO antigens on red blood cells). Passive agglutination is a test used to detect antibodies in the patient's serum. This differs from direct agglutination in that particles do not naturally express the antigens on their cell surface. Rather, the antigen of interest is coated on the particle (e.g. thyroglobulin).

2.15 Discuss the major cells and molecules involved in the adaptive immune response.

Discrete sites on antigens called antigenic determinants or epitopes are recognized by lymphocytes. B cell can recognize epitope alone. T cell can recognize epitope only when it is associated with an MHC molecule on the surface of a self-cell (either an antigen presenting cell or an altered self-cell)

Gut Associated Lymphoid Tissue (GALT)

A MALT region that contains columnar epithelium cells interspersed with goblet cells and intraepithelial T cells lining the small intestines. The mucus secreting goblet cells deposit a protective layer of mucus that separates and protects the cells of the luminal lining

Calnexin (Cx)

A chaperone protein that newly synthesized MHC I alpha chains bind to. The Cx retains the MHC I molecule in a partially folded state within the ER until it binds to B2M The binding of B2M to the MHC I product causes it to dissociate from Cx and bind to TAP-1

Conjugate vaccines

A conjugate vaccine is created by covalently attaching a poor antigen to a strong antigen thereby eliciting a stronger immunological response to the poor antigen. Most commonly, the poor antigen is a polysaccharide that is attached to strong protein antigen. However peptide/protein and protein/protein conjugates have also been developed.[1] B cell response to a capsular polysaccharide is T cell independent, meaning that B cells can produce antibodies without T cell stimulation.[2] By conjugating the polysaccharide to a protein carrier, a T cell response can be induced. Normally, polysaccharides by themselves cannot be loaded onto the MHC complex of antigen presenting cells (APC) because MHC can only bind peptides. In the case of a conjugate vaccine, the carrier peptide linked to the polysaccharide target antigen is able to be presented on the MHC molecule and the T cell can be activated. T cells stimulate a more vigorous immune response and also promote a more rapid and long-lasting immunologic memory.

Hypersensitivity Disease

A definable immune response that produces harm to the host as opposed to protection. Can occur due to inappropriate response to foreign material, excessive magnitude of response, prolonged duration of response, or the Innocent bystander effect where an immune cell displaying foreign antigens of a virus or bacteria is killed by the host immune response.

Explain the conditions that lead to a false negative when testing for antibodies in the patient (Precipitation)

A false negative will result if antigen is in excess so it is critical that the patient sample is diluted appropriately. No visible precipitation will occur if antibody is in excess

Beta2 microglobulin

A globulin that binds to, and stabilizes, the transmembrane portion of HLA A, B, C proteins.

Identify the steps of antigen processing that are negatively affected by Cytomegalovirus (CMV)

A member of the herpes family that infects immunocompotent individuals without causing symptoms. CMV encodes proteins that redirect newly synthesized class I MHC molecules from the ER back to the cytoplasm where they are degraded by the proteosome allowing the virus to remain in the host

The CD4+ T cell count contributes to the diagnosis of AIDs. What is the normal CD4+ T cell count?

A normal CD4+ count ranges from 500-1000 cells/mm3. When the CD4+ cell count is 350 cells/ mm3 it is time to consider treatment for HIV A CD4+ cell count fewer than 200 cells/mm3 is one of the qualifications for a diagnosis of AIDs.

What is a paraprotein? In what two biological samples may paraproteins be detected in a patient with multiple myeloma?

A paraprotein is an abnormal immunoglobulin (Ig) molecule or fragment of Ig molecule (e.g. light chain or heavy chain) produced by a malignant clone of plasma cells. In multiple myeloma, paraproteins may be detected in serum or concentrated urine.

Why is this assay termed "hemagglutination" assay?

A passive hemagglutination assay is one in which the particle is a tanned red blood cell to which an antigen has been passively bound. In the assay for rheumatoid factor, the antigen is, in fact, an IgG antibody- the target for rheumatoid factor.

Affinity Maturation (Somatic Mutation)

A process after immunization that leads to the gradual accumulation of higher affinity antibodies for the immunizing antigen. Production of these antibodies occur randomly as a result of random somatic mutations which give rise to point mutation Point mutations occur in the rearranged Ig VDJ gene region of both light and heavy chain. Somatic mutation occurs in germinal center 7-10 days following B cell activation

Acute Inflammatory Response

A protective innate response triggered rapidly by physical, biological, or chemical stimuli that results in the accumulation of plasma, plasma proteins, and leukocytes at the site of infection or injury.

Define Sensitization

A reaction in which specific antibodies develop in response to an antigen. Allergic reactions result from excess sensitization to a foreign protein. Sensitization can be induced by immunization, in which a pathogen that has been made noninfectious is introduced into the body.

Inflammation

A response of living tissue to damage of vascular tissue. Its purpose is to deliver defensive materials into the damaged areas.

Lymphatic system

A set of vessels in the body that runs alongside the vessels of the circulatory system. It is a one-way system, with lymphatic capillaries beginning at the tissues and ultimately emptying into the large veins near the heart. It serves to return excess tissue fluid (lymph) to the circulatory system, and filters the fluid through millions of white blood cells on its way back to the heart flow of lymph is passive and goes against gravity traveling upward

complement system

A system of more than 30 plasma and cell surface proteins that contributes to destruction of microbes through the generation of effector molecules that enhance innate and adaptive responses. Once initiated, complement activation is enzymatically regulated and production of the end-products occurs explosively and dramatically.

Complement System

A term used to describe a family of proteins that facilitate elimination of microorganisms (especially extracellular bacteria). The system is comprised of many activation and regulatory proteins synthesized by the liver and many of these proteins circulate as dormant enzymes until they are sequentially activated by cleavage.

Nuclear factor kappa B

A transcription factor activated when PAMPs bind to Toll-like receptors, resulting in cell activation.

Mannose receptors

A type of pattern recognition receptor that mediates phagocytosis of microbes after binding PAMPs containing mannose polymers

20.1 Discuss immune responses that prevent virus infection, specifically the role of: antibodies and complement

AB -neutralizes viruses which prevent virus from binding to specific receptors of host complement: -blocks attachment of some viruses to susceptible host cells -antibody/complement coated virus particles get phagocytosed -lyses enveloped viruses

Blood agglutination rxns:

ABO antibodies are IgM; Rh are IgG

Describe the classical precipitation curve in terms of: antibody excess

AKA postzone Too many antigens present in serum preventing the antibodies from cross linking to form lattice structure, preventing precipitate formation

Describe the classical precipitation curve in terms of: antibody excess

AKA prozone Too many antibodies present in serum preventing the precipitate to form due to inability to form a lattice structure

Discuss the experiment demonstrating that T cells recognize the processed peptide antigens presented by MHC

APCs after fixation then introduction to Ag did not activate T cells; Ag introduced before fixation activates T cells; fixation then introduction of Ag peptides activates T cells; T cells recognize processed Ag peptides presented by MHC

Dendritic cells

APCs classified according to location; capture Ag in tissues then go to lymphoid organs to present to T lymphocytes Langerhans-skin Interstitial-connective tissue of most organs Interdigitating-in lymphoid tissues Circulating-bloodstream Follicular-lymph nodes

what happens if the APCs haven't been exposed to the microbe?

APCs that have not been exposed to microbes may not express enough B7 to sustain T cell activation.

What does abnormal production of BLyS lead to and what are the three clinical disorders in which abnormal production of BLyS has been documented?

Abnormal production of BLyS alters immune tolerance allowing the survival of autoreactive B cells leading to autoimmune disorders. Rheumatoid Arthritis, Systemic Lupus Erythematosus and Multiple Sclerosis are the three clinical disorders associated with abnormal BLyS production

Spleen absence or dysfunction

Absence of marginal zone IgM secreting plasma cells makes susceptible to encapsulated bacteria; encapsulated bacteria are protected from phagocytosis by PRRs of innate immunity, so they need the IgM Abs to bind and mount a response

Discuss TCR accessory molecules

Accessory molecules strengthen interaction between T cells and APCs/target cells; and signal transduction (e.g. CD2 on T cells interact with LFA-3 on APC)

What are TCR accessory molecules?

Accessory molecules strengthen interactions between T cells and APCs/target cells; and signal transduction (e.g. CD2 on T cells interact with LFA-3 on APC)

what triggers the acute inflammatory response seen from the early stages of gingivitis?

Accumulation of bacteria below the gingival epithelial layer

Lymph nodes

Act as a type of filter for material collected from interstitial space. "lymphocyte meeting spots"

Discuss cellular events of affinity maturation in the germinal center

Activated B cells undergo intense proliferation in dark zone of germinal center; proliferating B cells are called centroblasts which (if having high affinity) mature to centrocytes whose Ag-Ab complex interacts with follicular dendritic cells (without Class II MHC) that positively select centrocytes in light zone and class switches to plasma or memory cells, resulting in mature B cells with high affinity for the Ag

what happens to activated T cells?

Activated T cells secrete interleukin-2 (IL-2) and develop the high affinity IL-2 receptor (IL-2R)!

what does activated Th1 cells secrete?

Activated Th1 cells secrete TNF, IL-2, and IFNy and support immune responses in which macrophages, natural killer cells and CD8+ T cells are effector cells and these type 1 cytokines are required for immunity against viruses, parasites, fungi and intracellular bacteria

What does activated Th2 cells secrete?

Activated Th2 cells screte IL-4, IL-5, IL-6, IL-10, IL-13, & TGFB These support antigen induced B cell differentiation to plasma cells and support isotype switching to IgG1 and IgE. ( IL-10 dampens Th1 response by inhibiting IL-12 secretion by APC preventing IFNy production. It also down regulates iNOS)

Specify the cytokines that the activated dendritic cell secretes. Explain the effect of each of these on the natural killer cell (NK cell).

Activated dendritic cells secrete cytokines IL-12, IL-15 and IL-18. In the presence of IL-12 (enhanced by IL-15 and IL-18) NK cells are activated and secrete IFNy which plays a critical role in Th1 cell formation

What do activated macrophages do? What does this lead to?

Activated macrophages secrete IL-12 induces TH1 response IL-18 made by macrophages + IL-12 stimulates TH1 cells to secrete more IFN-γ IFN-γ in turn recruits and activates more macrophages This self-perpetuating response may be a beneficial and protective response or it may be a detrimental response and cause extensive damage to tissues

Activated mast cells lead to...

Activated mast cells lead to amplification of IgE - IgE secreted by plasma cells bind to a high-affinity Fc receptor, Fc∑R1 on mast cells - Activated mast cells provide contact and secreted signals to B cells to stimulate IgE production

B Cell Clonal Expansion

Activated naive B cells undergo clonal expansion that is detectable within 24h of immunization. Following intial burst of proliferation activated B cells and T cells migrate to primary follicles where enhanced proliferation of B cells lead to germinal centers (Differentiation to plasma cell stage occurs 4 days after immunization and plasma cells secrete IgM)

tight binding

Activated neutrophils then undergo "tight binding" or adhesion to the vessel surface where the rolling slows dramatically.

what does activation of PRRs cause?

Activation of PRRs stimulates phagocyte activation (phagocytosis, production of antimicrobial molecules, and cytokine production).

what results from activation of complement in the innate immune systems response to gingivitis?

Activation of complement generates anaphylatoxins (C3a, C5a).

effector phase

Activation of effector T cells by microbe-infected macrophages. Activation of T helper cells by B cells for a humoral response.

priming phase

Activation of naïve T cells by DCs (primary adaptive response).

what results from activation of neutrophils by PAMPS in the innate immune systems response to gingivitis?

Activation of neutrophils by PAMPs leading to secretion of proteolytic enzymes and production of ROS.

what results from activation of PAMPS in the innate immune systems response to gingivitis?

Activation of resident macrophages by PAMPs leading to production of IL-1, TNF-a, and chemokines (CXCL8).

lymphocytes role in immune response

Adaptive responses are carried out by B and T cell lymphocytes

Severe Combined ImmunoDeficiency (ADA)

Adenosine Deaminase Deficiency (ADA) lead to metabolites deoxyATP and deoxyadenosine levels increase- toxic Early onset of infections, mainly of the respiratory tract and gut (bacterial, viral, fungal). Failure to thrive. Adenosine deaminase converts deoxyadenosine, (toxic to lymphocytes), to deoxyinosine which is not harmful. Treatment: Peg-ADA Gene Therapy, Bone Marrow Transplant or IVIG

Discuss antibody suppression

Administration of antibodies specific for an antigen to an animal before, or a few days after immunization with the same antigen, leads to a reduced immune response (100-fold lower response) - Passively administered antibody removes antigen from circulation leading to very low antigen available for specific B cell clone - Ag-Ab complex bound on the Fc receptor of B cells reduces signaling by the B cell receptor Vaccine: Measles and mumps are not administered to infants before 1 year of age: circulating maternal IgG for these antigens are present in this initial period

Discuss affinity maturation relevant to somatic hypermutation:

Affinity Maturation: occurs in germinal center of the lymph in secondary follicle somatic hypermutation of Ig genes is random and produces high and low affinity mIg It is followed by selective survival affinity maturation follows both of the processes listed above^ B cells with high affinity are positively selected in the germinal center B cells with low affinity undergo apoptosis

What is affinity maturation in relevance to somatic hypermutation?

Affinity maturation: Antibodies increase the affinity for antigens by somatic hypermutation - the result of somatic mutation of Ig genes followed by selective survival of the B cells producing the antibodies with high affinity - occurs in case of persistent or recurrent antigen exposure -Somatic mutation= ~0.001/bp/cell division --million-fold greater than normal mutation rate --somatic mutation is random --generates both high and low affinity MIG for antigen --> cells with high affinity are positively selected for in the germinal center --> cells with low affinity die in the germinal center

Affinity vs. Avidity

Affinity refers to the strength of any given bond between an antibody and its antigen. However, some isotypes of antibodies are multivalent and bind to multiple antigens. The strength of that overall connection is the avidity. i.e. IgG and IgM might have the SAME affinity for an antigen, but IgM will have greater Avidity because it has more binding sites since it is pentameric.

Define the terms affinity and avidity as they apply to antigen-antibody interaction

Affinity: The strength of the interactions between one antigen binding site and antigen. Avidity: The overall binding energy of all antigen- binding sites with antigen (Hydrophobic and ionic bonds mediate these interactions)

Discuss TCR-mediated signal transduction

After CD3 complex interacts with MHC-Ag, CD4/8-associated p56Lck phosphorylates ITAMs of zeta chains creating a docking site for ZAP-70, which allows for transcription of several gene products that lead to differentiation, proliferation, and cytokine secretion

where are leukocytes found in the lymph system?

After naïve B and T cells are formed by hematopoiesis, they enter lymph nodes from the bloodstream by passing through through specialized cells in high endothelial venules. B cells are located in follicles that exist beneath the outer capsule; T cells and other cells are located between the follicles and towards the center of the node.

After subsequent exposure of antigen, the TH1 cells secrete a variety of ____

After subsequent exposure of antigen, the TH1 cells secrete a variety of cytokines and chemokines. These factors attract and activate macrophages which function as primary effector cells in DTH.

Activation in spleen

Ag enter spleen through splenic artery to marginal zone---Ag trapped by interdig & carried to PALS---interdig present Ag (w/MHC II) to TH cells---activated TH and B migrate to marginal zone to 1' follicle---1' to 2' at germinal center

Activation of B cells

Ag enters lymph node and trapped by interdigitating dend cells---these cells present Ag to TH in paracortex---some activated TH and B cells go to cortex interact w/primary follicle---follicular dend cells, B, and TH cells induce secondary follicles---plasma cells differentiate in germinal centers & migrate to medulla to leave

Immunogen

Ag that evoke immune response

Define antigen- dependent phase of B cell development

Ag-dependent stage of B cell development - after Ag encounter, B cell activates and matures to Ab-secreting plasma cells and memory cells

Define antigen- independent stage of B cell maturation

Ag-independent stage of maturation - progenitor B cell matures and starts expressing mIgM and mIgD

What do agglutination techniques detect?

Agglutination techniques are simple in vitro methods that can be used for detecting antigens or antibodies in the patient's serum sample (Agglutination techniques involve the aggregation of particles as a result of antigen-antibody binding which can be visualized with the naked eye.)

Immunoglobulins

Aka Antibodies, produced by B-cells and have antigen-specific receptor cells. Consist of 2 heavy chains and 2 light chains linked via disulfide bridges. 5 sub-types: IgM, IgD, IgG, IgA, IgE.

Specify the two mIg isotypes on all naïve B cells. Specify the regions that comprise the variable region of the light chain and heavy chain

All naive mature B cells express IgM and IgD on cell surface (heavy chain constant region) Light chain variable region = V & J Heavy chain variable region = V, D & J

genome

All the genetic information in an organism; all of an organism's chromosomes

Explain allelic exclusion and the net effect on the surface expression of mIg on a B cell.

Allelic exclusion is the successful rearrangement of a heavy chain variable region from one chromosome which inhibits the somatic recombination of the heavy chain variable region on the other member of the chromosome pair. The net effect of this is that all mIg present on the surface of any one B cell will have the same heavy chain variable region

What is the mechanism of Type I hypersensitivity?

Allergen exposure causes TH2 B-cell response leading to IgE production * Remember IL-4 is the cytokine that gives the communication to class switch to IgE from mast cell and TH2 cells. IgE binds to mast cells (or basophils) via Fc∑1 or Fc∑II(Pretend ∑ is an epsilon) which sensitizes the mast cells. Re-exposure causes IgE cross-linking on mast cells which leads to degranulation and release of vasoactive amines *they require this pre-sensitization*

Localized Hypersensitivity Reaction (Atopy):

Allergic Rhinitis due to airborne allergens symptoms include watery exudation of conjunctiva, nasal mucosa and upper respiratory tract (sneezing, coughing) 10% of the USA population is affected Allergic Asthma due to airborne allergens, dust, fumes, insect products, viral antigens reaction develops in the lower respiratory tract Anaphylactoid Reaction caused by exercise, certain drugs and chemicals that induce mast cell degranulation - Intrinsic asthma: induced by exercise or cold Food allergy affects upper or lower gastrointestinal tract symptoms vary: diarrhea, vomiting, asthmatic attack, urticaria (hives) Atopic dermatitis (allergic eczema) skin eruptions that are erythematous - skin lesions contain TH2 cells and increased numbers of eosinophils

Discuss the alloactivity of T cells

Alloactivity is the response to foreign MHC molecules (alloantigens); T cells respond to allografts (grafts from other members of the same species); polymorphism of MHC allows individuals of the same species to have unique sets of MHCs; direct allorecognition from foreign cells interacting with CD4/CD8, indirect allorecognition from APC processing allogeneic MHC and interacting with CD4

High endothelial venules (HEV)

Allows circulation from blood into the cortex and medulla and into the lymphatic vessels. HEVs are a Good indicator of a lymph node.

TCR heterodimer

Alpha and beta chains (majority of TCRs) or gamma and delta chains. An individual Tcell can express either an *alpha/beta* or *gamma/delta* but never BOTH. transmembrane (fixed onto membrane, not secreted) *heterodimer* composed of two disulfide-linked polypeptide chains.

What is the role of CTLA-4/CD152?

Also binds B7 family members (CD80/CD86) and is not expressed constitutively. Its expression peaks two days after the initial T cell activation and it disappears from the T cell surface by day 4 It has a higher affinity for B7-1 and B7-2 than CD28. CTLA4/CD152 is a negative regulator of T cell activation because it down regulates CD28 when activated (inhibition of T cell)

Antibodies

Also known as immunoglobulins are bi-functional molecules that are secreted by plasma cells and bind antigens

Three pathways of complement activation

Alternative pathway Lectin pathway Classical pathway

Membrane vs secreted Ig Expression

Alternative splicing of the RNA transcript produces Ig that lacks membrane exon needed for surface bound properties. So splicing determines section vs membrane bound antibody

Complement pathways

Alternative: spontaneously activated on microbial surfaces (host cells protected) Lectin: binding of MBL (mannose binding lectin) to terminal mannose residues on microbes Classical: binding of C1 to C1-sites on Fc regions of IgM/G all converge on C3

What is rheumatoid factor and what is the isotype of rheumatoid factor?

An autoantibody in serum of patients with rheumatoid arthritis. Rheumatoid factor targets the Fc region of IgG. Rheumatoid factor is generally of the IgM isotype.

phagocyte oxidase

An enzyme complex that stimulates formation of superoxide anion.

superoxidase dismutase

An enzyme found in phagocytes that sustains the activity of reactive opxygen species.

Opsonization

An immune response in which the binding of antibodies to the surface of a microbe facilitates phagocytosis of the microbe by a macrophage; releases opsonin

Chronic Granulomatous Disease

An inability to generate ROIs due to mutation in the NADPH oxidase complex. This is predominantly a male condition because 60% of the cases are x linked. This leads to chronic inflammatory site and walling of granulomas

Therapy for Immediate hypersensitivity rxns

Anaphylaxis: epipen...reverses action of histamine @ H1 receptor, relaxes bronchial SM contraction, incr. CO Bronchial asthma: corticosteroids (decr. inflam) and leukotriene antagonists (relax bronchial SMC contraction, reduce inflam) allergic diseases: densitization (unknown?),j anti-IgE ab, Anti-histamine, cromolyn (inhibits mast cell degranulation)

_____- diverse peptides bind to MHC molecules and have same/similar hydrophobic αα at several positions and anchor peptide into the cleft vary depending on Class I; allelic variants are generally hydrophobic aa are the main contacts between Class I and nonameric peptides

Anchor residue

Blood transfusions from incompatible groups can cause an immunological transfusion rxn, resulting in ____, ____, ____, and ____.

Anemia, renal failure, shock, and death

Transfuse type B cells into person with Type A cells=

Anti-B (IgM) in recipient destroys B cells (complement mediated lysis)

What happens with blood transfusions of Type B cells to a Type A individual?

Anti-B (IgM) in the recipient will destroy the B cells- complement mediated lysis

Explain why the presence of agglutination in the "detection" step indicates that the patient is NOT pregnant.

Anti-BhCG does not form a soluble complex because BhCG (antigen) is not present in a patient's urine that is not pregnant. (because there was no BhCG in the urine, antibodies are available to bind to BhCG coated latex particles)

Regarding the "reaction step", why is the reaction not visualized even though an antigen-antibody complex form?

Anti-BhCG forms a soluble complex with BhCG present in the patient's urine because the patient is pregnant. Because the antigen-antibody complexes above are soluble, they do not agglutinate. Therefore, the reaction is not detected. (Agglutination Inhibition used to confirm pregnancy)

Name one autoimmune disorder that may result in a false positive result according to your Immunodiagnostic Notes. (VDRL Test)

Anti-cardiolipin antibodies are also present in the serum of some patients who do not have syphilis. Therefore, false positive results may occur in patients who are either pregnant, aged, have certain infections, or have Systemic lupus erythematosus

Type II is mediated by what?

Antibodies IgG or IgM predominantly mediate the destruction of cells to which they bind. - activation of the classical complement pathway and MAC formation leading to cell lysis

soluble effectors of the adaptive immune system

Antibodies (Humoral Immunity)

What happens with repeated blood transfusions of compatible ABO blood units?

Antibodies are developed against minor blood group antigens - Delayed hemolytic anemia - 2 to 6 days, mediated by IgG

Why are human antibodies injected into animals?

Antibodies that recognize the Fc portion of human antibodies are used in clinical laboratories. To generate these antibodies the human antibody must be injected into an animal. When (animal) antibodies are generated that recognize the (human) antibody Fc region/constant region, the antibodies are anti-isotypic antibodies. (Antibodies that bind Fcγ are anti-Fcγ antibodies; antibodies that bind Fcε are anti-Fcε antibodies)

What happens when two IgE molecules of the same specificity are close together?

Antigen binding results in cross linking and degranulation of the basophil or mast cell resulting in the release of histamine and IL-5. (cross linkage of adjacent IgE molecules must occur to initiate degranulation)

What is the initiating stimulus for B Cell Activation? Specify the consequence and significance of BLyS-BR3 interaction on B cell activation and clonal expansion

Antigen induced crosslinking of mIg in the BCR complex. This upregulates BR3 (receptor expressed on naive B Cells). Interaction of BR3 with its ligand BLyS prevents apoptosis of the B Cells allowing them to be activated and clonally expanded

Describe the role of an antigen-presenting cell in an immune response.

Antigen presenting cells deliver antigens to T Cells. An antigen must be displayed within the groove of the antigen presenting molecules. Macrophages and B cells are also APCs but they only present to CD4+ T cells that have been primed in a primary immune response (via dendritic cells). (dendritic cells are the most effective for primary immune responses and deliver antigens to CD4+ T cells)

Dendritic Cells

Antigen processing and presentation in adaptive immune response. Derived from CD34+ bone marrow hematopoietic stem cells in response to GM-CSF.

What are the properties of antigens and which molecules are the most immunogenic?

Antigens are foreign, chemically complex and they have a molecular weight greater than 6kD. Sequence of immunogenicity: Proteins > Polysaccharides > Nucleic Acids > Lipids (Proteins are the most immunogenic)

T-independent (Monoclonal Activator)

Antigens that can induce naive B cell activation in the absence of interaction with T cells. B cell activation in response to T-independent antigens leads mainly to IgM production. Examples are lipopolysaccharide (LPS) - when used at low concentrations and pneumococcal polysaccharide (from streptococcus pneumoniae)

Activators of immune response

Antigens: an antigen refers to a molecule that is capable of binding to the product of that immune response. Haptens: a small molecule that, when combined with a larger carrier such as a protein, can elicit the production of antibodies that bind specifically to Immunogens: immunogen refers to a molecule that is capable of eliciting an immune response by an organism's immune system. Note: All antigens are immunogens, but immunogens don't have to be antigens e.g. lipids, polysaccharides etc. ALL REQUIRE FOREIGNNESS, A MOLECULAR WEIGHT OF AT LEAST 1000 Da, DEGRADABILITY, AND CHEMICAL COMPLEXITY

how do Type I interferons (IFN-a, IFN-b) initiate a viral response?

Antiviral response- IFN-a or IFN-b produced by virus-infected cells protects uninfected neighboring cells from becoming infected! Virus-infected cells secrete type I interferons after viral nucleic acids activate intracellular TLRs. Type I interferons bind to interferon receptors on uninfected cells, which turns on genes whose products inhibit viral replication and assembly.

Immunogen

Any substance capable of inducing an immune response

Apoptosis vs. Necrosis

Apoptosis: -programmed cell death after phagocytosis -no inflammation -highly regulated by a family of genes Necrosis: -cell death because of injury -cell contents released -inflammation occurs

Complementarity determining regions- CDRs

Arise from various recombinations of VDJ segments. CDRs form the antigen binding pocket, paratope, which is the region for high antigen specificity. 3 contact points in one heavy chain (6 for heavy chain pair) and 3 contact points in the light chain (6 for light chain pair) comprise these CDRs.

Innate immunity

Arm of the immune system that is *present from birth and present before the onset of infection* that constitutes *non-specific immune mechanisms* for defense against pathogens.

_____ reactions are localized type III hypersensitivity reactions: - An inflammatory reaction induced by injection of an Ag in an individual with high levels of circulating Ab specific to it -- Swelling and localized bleeding at injection site -- Peaks 4-10 hours post injection --- May take place after a rapid, localized type I reaction to an insect bite ---May develop in lungs after inhalation of Ag >> For example, farmer's lung from moldy hay

Arthus reaction

Memory Cells

As the infected cells are eliminated from the body the stimulus to T cell clonal expansion digresses and most of the activated T cells begin to die Others become dormant and act as memory cells capable of a more rapid response upon second exposure to the same pathogen

Activation of C1 or MBL in complement cascade

Association of atleast 2 of the C1 or MBL heads w/Fcs of IgM/G or carbohydrates (MBL); activation of serine proteases that cleave the next copmlement component both activated C1 and MBL/MASP (MBL Associated Serine Proteases) results in cleaveage of C4 and C2-->C4b2b

At what point to all three pathways converge?

At MAC formation - leads to large channel or pore being formed in the target cell ---> killing of the target cell by loss of water and electrolytes

Define Lattice Formation

At the onset of the antigen-antibody reaction, an invisible formation of antigen and antibody complexes occurs. A lattice of soluble complexes slowly develops and gradually expands into a visible precipitate (lattice formation) as the antibody and antigen reach a zone of equivalent concentration.

What is atopy and the effect on individuals who have it?

Atopy is an ability to show an exaggerated tendency to mount IgE reponses to a wide variety of common environmental allergens Atopic individuals have higher total IgE levels in the circulation and higher eosinophil levels than their normal counterparts.

Explain the rationale for choosing a direct Immunofluorescence assay/test (DIA/DIT) instead of an indirect fluorescence test

Autoimmune antibodies that are bound to specific tissues may not always be present in circulation. DIA/DIT may be used to detect antibodies or immune complexes deposited in a patient's biopsy sample.

Name 4 pathological conditions for which a physician would request a Direct Coombs test

Autoimmune haemolytic anaemia (premature destruction of a patient's red cells) Erythroblastosis foetalis: (newborn's red cells express maternal anti-Rh antibodies) Drug induced haemolytic anaemia (e.g. Methyldopa, a prescribed anti-hypertensive) Chronic Lymphocytic Leukemia (CLL)

What down regulates TH17 cells

Autoreactive CD4+ Th17 cells are highly pathogenic, causing inflammation and severe autoimminutiy in animal models. Down regulation of TH17 is mediated by type 1 cytokine IFNy and Type 2 cytokine IL-4

Type 4 Hypersensitivity

Delayed type hypersensitivity reactions. T-cell and Macrophage mediated. Ex: Tuberculosis

DiGeorgeSyndrome

Deletion of a portion of chromosome 22. Various tissues affected and decrease in T cell numbers. Failure to thrive, frequent infections (viral, fungal, bacterial); Fatigues easily; Parathyroid glands, heart, & thymus may be affected; Physical abnormality varies; Allergies and asthma common May be apparent at birth, in infancy, or early childhood depending on severity of defect and which organs affected. B cell responses need T cell help and so are also affected. Treatment: Antibiotics; if severe thymic transplant

Explain why HIV can infect dendritic cell

Dendritic cells also express CD4 a molecule that determines T cell lineage and function on T cells. However, CD4 is one receptor for HIV Type 1. Infection of HIV-1 is initiated by interaction of viral envelope proteins with two receptors, the CD4 molecule and a chemokine receptor (CCR5 or CXCR4). Immaure dendritic cells express both of these.

Clonal selection

B and T cells that recognize antigens in a lymphoid organ stop in place and divide, forming clones of up to 10k cells; these also differentiate into effector cells (B cells make plasma cells)

cells in the adaptive immune system

B cell activation (Humoral Immunity) T cell activation (Cell-mediated immunity, and T cell help).

CXCR5

B cell chemokine receptor; similar to CCR7 for T cells brings B cells to follicles in the lymph node, rather than T cell zone

What is the bone marrow?

B cell development occurs during embyronic development in the liver and is maintained later in the bone marrow -not all mammals have bone marrow, cattle and sheep use Peyer's patch In humans, B cell development is complete and B cells are functionally mature when they exit the bone marrow (primary lymphoid organ)

Central B cell tolerance

B cells expressing self-reactive BCR in marrow undergo receptor editing (via add'l rearrangement of IgL locus); if not successful, cell dies by apoptosis or anergy (apoptosis if it binds cell-bound antigen; anergy if autoreactive against soluble antigen)

What do lymphoid immunodeficiencies involve?

B cells or T cells, and in combined immunodeficiency, they are both affected

T-cell and B cell cooperativity

B cells require TH activation to progress to an antibody producing plasma cell. CD40 is a critical ligand/receptor interaction needed for isotype switching. IL-4 promotes B-cell growth. IL-6 promotes B-cell proliferation.

Describe immature dendritic cells with respect to (a) development and in vitro conditions leading to generation of dendritic cells.

Dendritic cells are highly potent antigen presenting cells that are derived from CD34+ bone marrow stem cells. It is unclear which precursor cells they arise from. In vitro GM-CSF, IL-4 and flt3 ligand stimulate production of dendritic cells from CD34+ stem cells. The flt3 ligand is a cytokine and a growth factor that stimulates the proliferation of hematopoietic cells. The FMS like tyrosine kinase 3 (FLT3) is its receptor. (FLT3/CD135 regulates differentiation, growth and survival of CD34+ progenitor cells)

2.13 (2) Discuss humoral immune response and cell-mediated immune response. HUMORAL

B lymphocytes recognize antigenic epitope -mediated by B lymphocytes that have surface Ig that recognize specific antigenic epitopes - cells proliferate and differentiate into plasma cells that secrete antibody or immunoglobulin that binds to specific antigen

T-Independent Response

B-cell activation without the normal TH-cell assist mechanism. Occurs when an antigen has many repeating polymerized epitopes that stimulates B-Cell activation of ONLY IgM isotypes. DOES NOT GENERATE IMMUNOLOGICAL MEMORY.

Germinal center of a secondary follicle; what happens?

B-cell differentiates and induces low levels of Ab secretion; 3 processes 1) IgM-->G, A, E (AID) 2) somatic hypermutation (AID) 3) generation of memory B cells

secondary lymphoid tissue associated with respiratory epithelium- bronchus

BALT

B cell activation (general)

BCR engagement + CR2:C3d or TLR:PAMP Can then go through T-dependent antigen B cell activation or T-independent antigen B cell activation

Discuss B cell receptor (BCR) and the signaling pathway mediated upon antigen binding

BCR: antigen binding mIg causes activation of signal Ig-a/Ig-b heterodimer; phosphorylation of ITAMs by tyrosine kinases and begins transduction pathways; leads to changes in gene expression, functional cell changes, differentiation, and activation

What are the three receptors that BLyS binds to?

BR3, BCMA and TACI which are present on most peripheral B cells. Interaction with BR3 has the greatest affinity. BR3 binding leads to B cell survival by preventing apoptosis.

Protective actions by the innate immune system

Barrier epithelial cells Extracellular pathogens are destroyed by phagocytes, complement proteins, and antimicrobial molecules. Antiviral response

ABO Blood System

Based on the expression or lack of the A and B polysaccharides on the surface of RBCs Persons maybe classified as Type A, B, AB or O. Humans have IgM antibodies (IgM Iso-hemagglutinins) to the A and/or B antigens following immunization with cross reactive antigens on bacteria that compromise natural gut flora.

________ - Initiate TH2 Response and Production of IgE - make up only like 1% of white blood cells - recruited to tissue and activated by Toll-Like Receptors that are present on the mast cells - then recruited to secondary lymphoid tissue and leads to TH2 response - they secrete TH2 cytokines and IL-4 and IL-13 (like mast cells) that amplify TH2 cell response - They express CD40L which binds to CD40 on activated B-cells which leads to class switch to IgE (and IgG4)

Basophils

Describe basophils with respect to half-life and % of circulating leukocytes in a normal, healthy patient

Basophils are circulating cells with a half-life of 2.5 days. Less than one percent of circulating white blood cells are basophils.

Lymph nodes

Bean-shaped filters that cluster along the lymphatic vessels of the body; function as a cleanser of lymph as wells as a site of T and B cell activation; first lymph tissue to encounter Ag Cortex-outermost containing primary follicles, macrophages, and dendritic cells; primary follicles develop to secondary at germinal center w/ Ag present; thymus-independent Paracortex-middle populated with T lymphocytes and interdigitating dendritic cells; thymus-dependent Medulla-innermost populated with activated lymphocytes and plasma cells

Explain why detection of ANA antibodies using this technique is a screening test and not a confirmatory test.

Because these ANA antibodies can also be found in other diseases

What antigen is used in the agglutination inhibition test for pregnancy?

BhCG

Regarding antibodies: Explain what is meant by bifunctional molecule and specificity

Bifunctional Molecule: Antibodies possess both antigen bnding capacity and biological activity Specificity: Antigen binding takes place in the variable region and amino acid differences in this region lead to specificity in terms of antigen recognition and binding

N-formyl peptide receptors

Bind peptides containing N-terminal formyl-methionine-leucyl-phenylalanine (FMLP) residues, which are potent stimulators of the respiratory burst and chemotaxis.

Inhibitory T cell receptors

Bind to B7 molecules on APC and induce anergy: CTLA4, PD-1 PD-1 on T cell binding to PD-L1 on cancer cell induces CD8+ cell to die, even if B7:CD28 interaction is occuring

what initiates signal one of T cell activation?

Binding of MHC/peptide to the TCR initiates signal 1

Name the "stress- induced" ligand that allows NK cells to destroy target despite normal expression of Class I MHC

Binding of NKG2D (activating receptor) to "stress-induced" ligands MICA on target cells can lead to destruction of that target despite normal expression of Class I MHC on the target. (MICA may be up regulated on virally infected cells, cancer cells and during stress. (MICA= MHC class I chain-related gene A))

Explain why blocking PD1 might be detrimental to a patient with an autoimmune disorder

Blocking PD1 might be detrimental to a patient with an autoimmune disorder because this would lead to a decrease in negative signaling which is needed to cause T cell exhaustion to prevent immune mediated tissue damage

Explain why blocking PD1 signaling can lead to tumor regression

Blocking PD1 signaling can lead to tumor regression because engagement of PD1 delivers a negative signal to T cells that eventually leads to T cell exhaustion so blocking PD1 so that it can't bind to its ligands inhibit negative signal and T cells recover their ability to secrete cytokines, proliferate and destroy viral infected and cancer cells

purpose of blood vessel dilation in neutrophil recruitment

Blood vessels dilate to increase blood flow to the site of infection (due to histamine and other inflammatory mediators).

Explain the role of the two primary lymphoid tissues

Bone Marrow: Hematopoiesis of myeloid and lymphoid cells. After birth the bone marrow gives rise to monocytes, granulocytes, eosinophils and basophils. Dendritic cells and mast cells are also derived from here. Thymus: Where T cells mature

FcεR1 Receptor and the types of forces that play a role in the interaction of antigen with IgE and between FcεR and Fcε.

Both basophils and mast cells express this IgE high affinity receptor. This receptor binds to the Fcε (IgE Fc region) and bind free IgE antibodies. This FcεR1 and Fcε interaction is non covalent and relies on ionic and hydrophobic interactions. Binding is reversible like the interaction between antigen and IgE.

Role of Proteolytic Fragments ( C2b)

C2b is produced by C1 acting on C2 in the classical pathway. C2b is a weak kinin that increases vascular permeability, and in doing so contributes to the genesis of inflammation.

State the order of major reactants in all three phases of complement activity

C3 convertase C3b C5 convertase C5b MAC

What are the activators involved in the Alternative Pathway?

C3 molecules are repetitively hydrolyzed in serum to C3a and C3b revealing binding sites for Factor B on C3b, in presences of Mg

Role of Proteolytic Fragments (C3a, C4a, and C5a )

C3a, C4a, and C5a are anaphylatoxins generated by the action of the C3 and C5 convertases on the complement proteins C3 and C5. They cause mast cells and basophil degranulation (release of histamine and other inflammatory mediators) C5a is also chemotactic for neutrophils, recruiting these cells to the site of infection. (C4a is generated only following activation of the classical pathway.)

Complement effector functions

C3b can function as an opsonin (A) to enhance phagocytosis. C3a and C5a are anaphylatoxins (symptoms of inflammation). The membrane attack complex (MAC) causes microbe lysis (C).

Role of C3b in complement reactions

C3b fragment can attach to microbes and immune complexes, then bind to CR1 on phagocytes, erythrocytes, or B cells; RBCs internalize immune complex and migrate to spleen where the complexes are cleared

Role of Proteolytic Fragments (C3b)

C3b has numerous biological roles. When deposited on microbial surfaces it serves as an opsonin. When deposited on immune complexes it facilitates the elimination of immune complexes. Component of the alternative pathway C3 convertase (C3bBb). In addition, C3b is a component of the C5 convertases of both the alternative (C3bBbC3b) and the classical (C4b2a3b) complement pathways.

C5a attracts neutrophils

Naive T cell markers

CCR7: binds chemokines produced by stromal cells in T cell zone of PLO L-selectin: binds to L-selectin ligand on HEV to exit HEV into lymph node LFA-1: binds ICAM-1 on HEV, stabilizing cell-cell interactions Lack S1PRs activated effector T cells don't express CCR7 or L-selectin

Severe Combined Immunodeficieny (XSCID)

CD132 mutation resulting in failure to thrive. Recurrent and persistent infections (bacterial, viral, fungal). Lack of signaling via receptors for IL-2, IL-4, IL-7, IL9, IL-15, & IL-21 Other Name includes common gamma chain, IL-2R gamma chain, IL-2RG. Treatment: Gene Therapy, Bone Marrow Transplant or IVIG

What are the components of the B Cell Co-Receptor Complex

CD19, CD21 and CD81

Describe B cell co-receptor

CD19, CR2 (CD21), and TAPA-1 (CD81); CR2 is a receptor for complement breakdown component C3d; mIg w/ complement coated Ag binds to CR2, allows crosslink between BCR and co-receptor complex; all enhance the B cell response

non-classical Class I MHC

CD1; lipids or glycolipids can act as Ag

Expression of CD2 (Thymic Cortex Process)

CD2 is one of the first molecules to be expressed on the cell surface of the T cell after the progenitor migrates to the thymus and remains a T cell marker for the life of the T cell however it is not T cell specific. CD3 is T cell specific!

CD markers on T helper cells

CD2, CD3, CD4, CD28, CD45

CD markers on T cytotoxic cells

CD2, CD3, CD5, CD8, CD28, CD45

CD markers on NK cells

CD2, CD5, CD8 (variable), CD16 (FcyIII), CD45, CD56

B cell markers

CD20: all B cell stages except plasma cells CR2: binds C3d CD19: involved in signal transduction CD40: binds CD40L on Tfh, req'd for class switching

IgE Receptor: 2) Low affinity Fc∑RII (with two isotypes: CD23 and CD23a)

CD23a - expressed on activated B-cells, alveolar macrophages, and eosinophils CD23 - expression on various cells by IL-4 - When Soluble form of CD23 binds with CD21 on surface of IgE synthesizing B-cells, IgE synthesis is increased - When Membrane-bound CD23 binds to soluble IgE, further IgE synthesis is suppressed

List two co stimulatory signal molecules present on T cells

CD28 - expressed on resting and activated T cells CTLA-4 (CD152) - expressed on activated T cells 2-3 days post-stimulation playing a role in T cell homeostasis

What is the role co-stimulatory signals on T cell activation? What are two co-stimulatory signals?

CD28 - expressed on resting and activated T cells CTLA-4 (CD152) - expressed on activated T cells 2-3 days post-stimulation playing a role in T cell homeostasis - interaction of CTLA-4 (CD152) on helper T cells with B-7 on APC leads to inhibition of activated T cells (Uthay describes as being like brakes on a car... the f*ck)

Explain the role of NK cells during a (a) CD4+ Thp cell activation

CD4 + Thp Cell Activation: NK cells play a critical role in differentiating Thp cells to Th1 cells via the intermediate ThO cell. NK cells are activated by dendritic cell derived IL-12 which cause them to secrete IFNγ which influences ThO differentiation to Th1 (GAMMA INTERFERON INFLUENCES THO DIFFERENTIATION TO TH1 CELLS)

where does CD4 T cell polarization occur?

CD4 T cell polarization occurs in secondary lymphoid tissues and is regulated by cytokines produced by APCs, the T cells themselves, other leukocytes, and /or other cell types

T helper cells

CD4 T cells (T helper cells) are responsible for cell-mediated immunity and for T cell help (contribute to activation of naïve B cells and naïve CD8 T cells).

how are CD4 T helper subsets are distinguished?

CD4 T helper subsets are distinguished by the cytokines they secrete (signature cytokines).

Discuss TCR co-receptor molecules CD4 and CD8

CD4 and CD8 are co-receptors because they recognize MHC-peptide complexes and play roles in signal transduction; CD4 distal domain binds to the hydrophobic pocket formed by α2 and β2 domains of MHC Class II; CD8 binds to hydrophobic pocket formed by α2 and α3 domains of MHC Class I with some contact with β2-microglobulin

Why does MHC Class II presentation stimulate CD4 T cells but not CD8 T cells (and vice versa)?

CD4 and CD8 are co-receptors that stabilize the interaction between T cells and APCs. MHC Class II on the APC binds to CD4 on the T cell, and MHC Class I binds to CD8!

T cell accessory membrane molecules

CD4 distal domain binds to hydrophobic pocket formed by α2 and β2 of Class II MHC CD8 binds to conserved region of α2 and α3 domain of Class I MHC

T regulatory cells

CD4+ T cells w/ CD25 (alpha chain of IL-2R) and the TF FoxP3; not deleted after negative selection in the thumus, and thereafter suppress activation of lymphocytes and APCs in periphery

what does CD40L do?

CD40 ligand (CD40L) on T cells enhances Signal 2. CD40L binds to CD40 on APCs, which stimulates expression of B7 molecules to make APCs better at activating naïve and effector T cells.

cytotoxic T cells

CD8 T cells (cytotoxic T cells) are responsible for killing virus-infected cells.

Classical pathway of macrophage activation

CMI; Th1 cells activate macrophages Th1 secrete IFN-gamma and express CD40L; macrophages then upreg expression of enzymes producing ROS/NO; cytokines like TNF; MHC molecules that present antigen to T cells; and IL-12, which reinforces Th1 differentiation at site of infection

Specify the cells on which (complement receptors) have been identified and the complement fragments that bind to each

CR1: Present on phagocytes, B cells and erythrocytes. Opsonin mediated recognition of antigen (phagocytes) and clearance of circulating immune complexes (erythrocyte). Binds to C3b, C3bi and C4b CR2: Present on B cells. Mode of Epstein Barr virus infection. Binds to C3bi CR3a/4a: Present on mast cells and basophils. Degranulation of these cells releasing histamine and other inflammatory mediators. Binds to C3a and C4a CR5a: Present on mast cells, basophils and neutrophils. Causes degranulation of mast cells and basophils and it is a chemotaxis for neutrophils. Binds to C5a

Discuss the enhancement of BCR signaling by co-receptors

CR2 recognizes Ags coated with C3d and makes a bridge to allow CD19 component of B cell co-receptor to interact with the Ig-α/Ig-β complex to amplify the signal

20.1 Discuss immune responses that prevent virus infection, specifically the role of: CTL cells

CTL specific activity 3-4 days after infection and peaks 7-10 days when more virions have been eliminated from the body

where are CTLA-4 (cytotoxic T lymphocyte antigen-4) and PD-1 (programmed cell death antigen-1 expressed and what do they do?

CTLA-4 (cytotoxic T lymphocyte antigen-4) and PD-1 (programmed cell death antigen-1) are expressed on all T cells and dampens T cell activation by binding to B7.

21.7 Discuss the HIV-1 infection in relation to cell types and receptors involved

CXCR4- coreceptor expressed by T cells with ligand SDF-1, important for T-cell activation, trafficking, and homing -HIV gp120 binds CD4 on target cell and a chemokine coreceptor for infection (CXCR4) CCR5 (CD195)- coreceptor by macrophages, dendritic cells, T cells with ligand RANTES/MIP-1alpha, MIP-1beta -HIV gp120 binds CD4 on target cells and chemokine receptor for infection expressed by macrophages, dendritic cells, T cells

What does the detrimental response entail?

Can lead to granuloma formation and multinucleate giant cells, release lots of lytic enzymes destroying surrounding cells - TB induces this from prolonged inflammation

Monoclonal antibodies treatment:

Cancer: anti-CD20 for B cell cancers Autoimmune diseases

Pernicious Anemia (Autoimmune Disorder)

Caused two different ways 1) Caused by anti-parietal cell H+/K+ ATPase Antibody which destroys parietal cells that secrete intrinsic factor. Anti-parietal cell binds to the gastric parietal cell. Leads to defective red blood cells (megablastic anemia). Can be investigated by checking serum B12 levels 2) Caused by anti-intrinsic factor AB that competes with B12 to bind to intrinsic factor leading to defective red blood cells (megablastic anemia. Can be investigated by checking serum B12 levels

HIV entry into cells

Causes direct and indirect destruction of the CD4+ cells. CD4+ is found on the surface of Th cells, macrophages and dendritic cells. CD4, CCR5 (macrophages) and CXCr4 (Th) can interact with HIV and allow entry into the cell (without CD4 cells there is a massive decrease in the immune response however the two T independent antigens still are able to have an immune response to HIV)

___________________: Peptides naturally produced from gluten do not bind MHC class II molecules An enzyme, tissue transglutaminase, modifies the peptides so they can now bind to the MCH Class I molecules The bound peptide activates gluten-specific CD4 T cells The activated T cells can kill mucosal epithelial cells by binding Fas, they also secrete IFN gamma, which activates the epithelial cells

Celiac disease

Discuss the role of the pre-T cell receptor complex

Cell becomes permissive for TCR α-chain locus rearrangement; stimulates expression of CD4 and CD8 coreceptors; stimulates proliferation; stops additional β-chain arrangement (allelic exclusion)

B Cell Receptor

Cell surface membrane Ig (SmIg) that recognizes and interacts with intact antigen; it is not linked to any signal transduction pathway.

Define Direct Agglutination

Cells (such as bacteria, fungus, and erythrocytes) and insoluble particulate antigens can be directly agglutinated by their specific antibodies. The antibody has two Fab arms with which it can bind to antigens on two cells. Likewise many antibody molecules bind with a number of cells to form a lattice. This lattice formation is seen visually as clumps. Hence, formation of clumps indicates the presence of antigen-antibody binding. Lack of agglutination indicates the absence of antigen-antibody reaction. *Direct agglutination tests use naturally occurring antigens on the surface of cells such as RBCs or bacteria

How does Fluorescent-Activated cell Sorting (FACS) work? What is an application of this test that we discussed in class?

Cells labeled with anti-bodies conjugated to fluorochromes are pushed into a stream where only one cell, and any antibodies that are bound to it, may intercept the laser beam at a time and are excited to a higher energy state. - this energy is released as a photon of light - the photon emitted has distinct spectral properties - computer interprets the data and presents a visual display Application:

Antigen presenting cells (APCs)

Cells that can ingest foreign molecules or pathogens and display the antigens on the cellular surface resulting in activation of humoral and adaptive responses. Includes: Macrophages, Dendritic cells, Langerhan's cells.

What is the difference between central and peripheral tolerance?

Central tolerance is the mechanism by which newly developing T cells and B cells are rendered non-reactive to self while peripheral tolerance is immunological tolerance developed after T and B cells mature and enter the periphery.

______ - helps bind Ag peptides to Class I MHC to get them to TAP pathways

Chaperone proteins

Complement C5a

Chemoattractant that initiates neutrophil migration and diapedesis along with IL-8

chemokines

Chemokines are a unique class of cytokines that regulate leukocyte migration.

List the chemokines and cytokines secreted by activated microphages

Chemokines: IL-8 (CXCL8) & MCP-1(CCL2) Cytokines: IL-1, TNF, IL-6, IL-12, IL-15, IL-18, IL-23, TGFβ

IL-8 (CXCL8)

Chemotactic factor recruits neutrophils, basos, TCells to site of infection.

7.2 Compare and contrast MHC Class I, Class II, and Class III products with respect to structure, function, and genomic organization.

Class I MHC genes - encode glycoproteins expressed on the surface of all nucleated cells, presentation of peptide antigens to Tc cells Class II MHC genes - encode glycoproteins primarily expressed on the surface of APC (such as B cells, macrophages, dendritic cells), presentation of peptide antigens to TH cells Class III MHC genes- encode various secreted proteins that function in immune response (i.e. components of complement, proteins involved in inflammation)

Discuss peptide binding by MHC class I molecules

Class I has α1 and α2 to function in forming the peptide-binding cleft that is closed at both ends (8-10 αα can bind in cleft), binds peptides to interact with CD8, digested in cytosol go through cisternae, and interact with ER; peptides derived from endogenous intracellular proteins; anchor residues (hydrophobic) keep peptides inside cleft. Most of the polymorphic aas are located in the pep-binding cleft of MHC molecule.

Discuss in detail the structure of MHC class I and II molecules

Class I has α1, α2, and α3 with β2-microglobulin, transmembrane domain and cytoplasmic tail. Encode polymorphic genes HLA-A,B, and C; Class II has two polypeptides, α-chain and β-chain each with own transmembrane domain and cytoplasmic tail

Discuss peptide binding by MHC class II molecules

Class II has α1 and β1 that function in forming the peptide-binding cleft that is open at both ends (13-18 αα can bind in cleft), binds peptides to interact with CD4, peptides derived from exogenous proteins (self or non-self.) No anchor peptides present.

Discuss clonal anergy

Clonal anergy - the inability of T cells to respond to MHC-Ag complex due to inhibition of signal 2; anergic T cells do not respond to APCs

what initiates signal 2 of T cell activation?

Co-stimulatory molecules provide Signal 2. Signal 2 is generated by the binding of CD28 on the T cell to B7 molecules (CD80, CD86) on the APC!

Alternative pathway of complement activation with C3 convertase

Complement activation requires generation of a C3 convertase- an enzyme that cleaves complement protein C3 to C3a + C3b. For the alternative pathway, the C3 convertase forms when C3b binds to a microbe! There is always a low level of spontaneous C3 cleavage in plasma, but C3b cannot bind to normal cells. When C3b binds to a microbe, it binds Factor B which is then cleaved to form the C3 convertase (designated C3bBb). Once formed, the convertase continually cleaves plasma C3 generating DRAMATIC amounts of C3a and C3b. Some C3bBb will bind another C3b to form the C5 convertase (C3b2Bb) The C5 convertase cleaves C5 to C5a + C5b. C5b binds C6, then C7, and C8 come together to form a complex that uses C9 to form a pore (membrane attack complex, MAC), in the microbe membrane. Water flows in through the MAC to cause lysis.

where can the complement system be activated?

Complement may be activated anywhere that microbes come into contact with blood plasma.

soluble effectors of the innate immune system

Complement proteins Antimicrobial metabolites

soluble effectors of the innate immune system

Complement proteins Antimicrobial molecules

Explain the role of complement regulatory proteins.

Complement regulatory proteins limit damage and deleterious effects on normal tissues that can be caused by the compliment system and act in a specific manner (do not protect xenografts)

Describe the high avidity adhesion interactions between a dendritic cell and a pCTL.

Conjugate formation between the target cell and the pCTL is stabilized by high avidity interaction of adhesion molecules CD2 and LFA-3, LFA-1 and ICAM1 & 2. Optimal activation of pCTL also requires CD8 binding to MHC I at site distinct from TCR/MHC I binding site

Red pulp of spleen

Consists of *splenic cords and splenic sinuses (aka the Cords of Billroth). * Look for *high concentration of RBCs* giving a very red color. *Specialized endothelial cell lining with fenestrated capillaries* in sinuses allowing RBCs to pass across. *Function of red pulp is the destruction of old worn out RBCs.*

Medullary Cords and Sinuses of lymph nodes

Cords are the more densely dark staining areas and the sinuses run between the cords indicating the flow of lymph fluid.

why/how does stress inhibit immune function?

Cortisol steroid made by adrenal cortex, inhibits productiona and function of any cytokines- caused by stress or autoimmune disease meds (prednizone etc, cant prescribe for long)

Define cross linking and cross reactivity

Cross linking: Process by which one antigen is bound by two antibodies Cross reactivity: when antibodies that have been generated to one epitope on an antigen can bind an epitope that is very similar on a different antigen

Graft rejection treatments

Cyclosporine (block T cell cytokine synth); rapamycin (block lymphocyte proliferation); CTLA4-Ig (inhibits T cell activation by blocking B7)

what regulates T cell differentiation (polarization)?

Cytokines (signal 3) produced by APCs and other cell types regulate T cell differentiation (polarization).

Identify the molecules and cells that link innate and adaptive immunity

Cytokines and antigen presenting cells serve as a link between innate and adaptive immunity.

Alpha or beta interferon

Cytokines that mediate the antiviral response.

Chemokines

Cytokines which act as Chemoattractants they have 2 adjacent cysteine motifs. Secreted by immune cells and react with other immune cells to mediate communication for immune response.

Discuss the cytosolic pathway

Cytosolic pathway: Protein degraded into peptides, transport peptides from cytosol to rough ER lumen, Class I molecule assembly and binding to peptide aided by chaperone proteins and transported out through TAP doorways and packaged at Golgi apparatus

Type 2 Hypersensitivity

Cytotoxic ANTIBODY mediated cell destruction Ex: Autoimmune hemolytic anemia

In general terms, what is the role of the thymus on T cell differentiation? Specify the cytokine that plays a role in thymocyte development. Specify the role of thymic epithelial cells.

During T cell migration through the thymus it (thymocyte) matures under the influence of cytokine IL-7. The T cell aslo expresses unique TCRs able to recognize antigenic fragments within the thymus when these fragments display Class I or Class II MHC molecules on them. Central Tolerance: TCR in the thymus are only reactive to foreign peptide - self MHC but not to self peptide/self MHC)

Selection of TCRs beneficial to the host

During this stage DP (CD4+ & CD8+) thymocytes are selected to live (positive selection) or selected to die (negative selection or death by neglect) depending on the interactive avidity of their own TCR with self-antigen/self MHC on thymic epithelial cells and other molecules expressed on the two cells

Identify the steps of antigen processing that are negatively affected by Epstein Barr virus (EBV)

EBV thwarts immune system by inhibiting the activity of proteosomes. By doing this the virus prevents hydrolysis of viral proteins into peptide size fragments. Only peptides of a suitable size can bind to groove of MHC 1 molecules (8-10 AAs). MHC peptide complex doesnt form and EBV remains safely in the B Cell

Describe in detail the segments of the variable regions of (a) TCRα, and (b) TCRβ.

Each T cell clone expresses receptors with the same constant region but unique variable regions. Variable regions are constructed from V, D and J segments via somatic recombination TCRa Variable Region: V and J segments TCRB Variable Region: V, D and J segments

Variable and Hypervariable regions

Each antibody has a variable region on each heavy chain, and each light chain. So for IgG which has 2 heavy and 2 light chains, it has 4 total variable regions. EACH VARIABLE REGION HAS 3 HYPERVARIABLE (HV) REGIONS. All of the HV regions for a given heavy and light chain pair make up what is known as the Complementarity determining region (CDR). So for example: An IgG has 2 heavy and 2 light chains. Each chain has 3 HVs, so 12 total. For each heavy and light chain pair, there are 6 HV regions, so there are 2 total CDRs.

What is the early stage of T cell maturation in the thymus?

Early stage thymocytes are called double negative (DN) cells because they do not express CD4 or CD8 (CD4-/CD8-) Early Phase involves expression of: C-Kit- receptor for stem cell growh factor CD44- cell adhesion molecule CD25- alpha chain of IL-2 receptor · Stage DN1 - c-Kit (+), CD44 (+), CD25 (-) · Stage DN2 - c-Kit (+), CD44 (+), CD25 (+); thymocytes proliferate, rearrangement of β, γ, and δ occurs but NOT α; cells destined to become γδ (5%) diverge here and become mature γδ T cells · Stage DN3 - c-Kit (-), CD44 (-), CD25 (+); c-Kit and CD44 expression turned off, cells stop proliferating; pre-T cell receptor complex forms (TCR-β + pre-T-α + CD3) which signals further proliferation and maturation; allelic exclusion of β-chain rearrangement · Stage DN4 - CD25 expression low, cells begin expressing CD4 and CD8 double positive (DP); rapid proliferation and no rearrangement of α-chain

Th17 cells

Effector cells initially shown to arise from ThO cells in the presence of IL-6 and TGFB. The combination of IL-1 and TGFB can also induce the differentiation of naive CD4+ T cells to Th17 cells IL-23 is required to stabilize the Th17 cell Th17 plays a role in the immune response against extracellular pathogens that are not eliminated by CD4+ Th1 and CD4+ Th2 effector cells.

List the antigen processing pathways

Endocytic and cytosolic

Discuss the endocytic pathway

Endocytic pathway: Ag engulfed and degraded in endosomes/lysosomes, invariant chain carries Class II molecule to endosome, invariant chain degraded to CLIP which is exchanged with exogenous Ag, transported to cell surface

_____ - processed by the cytosolic pathway within cells and presented by Class I MHC

Endogenous Ags

What are endogenous superantigens?

Endogenous superAg: cell membrane proteins encoded by infected virus

TNF on (a) NADPH oxidase, (b) iNOS, (c) vascular endothelium- with IL-1.

Enhances NADPH oxidase activity in phagocyte and plays a role in the activation of iNOS When combined with IL-1 it plays a role in inflammation by inducing vascular enothelium to secrete IL-8 (CXCL8) and MCP-1 (CCL2). It also induces de novo expression of VCAM-1, ICAM-1 and E-selectin and upregulates expression of ICAM-2 on vascular endothelium

Explain The Role Of The Chemokine Monocyte Chemotactic Protein -1 (CCL2/MCP-1)

Enhances the recruitment of monocytes into circulation and migration into tissue where they differentiate into macrophages following tissue damage or infection. (Under normal conditions monocytes comprise only 4% of circulating leukocytes)

Lymphadenopathy

Enlarged lymphnode due to cellular infiltration and edema.

Describe eosinophils with respect to differentiation in bone marrow, role of IL-5 and role of CCL11 (eotaxin). What cells secrete IL-5? Which cells secrete CCL11?

Eosinophils are granulocytic bone marrow derived cells that differentiate from a myeloid progenitor under the influence of IL-5 IL-5 is a cytokine derived from Th2, a subset of CD4+ T cells, mast cells and basophils (IL-5 released when these cells bind free IgE). CCL11 (eotaxin) is a chemokine released by epithelial cells and fibroblasts. Both IL-5 and CCL11 play a role in the increased release of eosinophils from the bone marrow to the tissues.

How do we treat anaphylactic shock?

Epinephrine. It counteracts the effects of the mediators such as histamine, leukotrienes. It relaxes smooth muscle, that reduces vascular permeability. Increasing cardiac output that prevents vascular collapse. Increasing cAMP which blocks mast cell degeneration.

how do epithelial barriers fight infections?

Epithelial cells form protective barriers to infection for skin and mucosal surfaces of the respiratory, gastrointestinal, and urogenital tracts. Mucosal epithelia (oral cavity, GI tract, respiratory tract, urogenital tract) produce mucus and antimicrobial peptides that impair microbial growth and kill microbes. Barrier epithelium contain intraepithelial lymphocytes.

_____ - processed by the endocytic pathway taken in by endocytosis/phagocytosis and presented by Class II MHC

Exogenous Ags

What are exogenous superantigens?

Exogenous superAg: soluble Ag secreted by bacteria, exotoxins from Gram pos bacteria, staphylococcal enterotoxins

Secondary Immune Response

Exposure to the same antigen a second time which activates the differentiation of memory B cells. This response has a shorter lag time, leads to higher antibody titer, secretion of the new isotype and can occur anywhere in the body

Mast cells express what type of receptors?

Express Fc Receptors with high affinity for IgE, IgG, IgA, toll-like receptors (these toll-like receptors activate and recruit basophils to the infected tissue and that in turn activates TH2 which will cause the class switch into IgE of B-cells in the secondary lymph organ)

Component of a preTCR complex (Thymic Cortex Process)

Expression of a viable TCR that is tolerant to self proteins/self MHC beginning with somatic recombination and allelic exclusion, rearranged TCRB chain, subsequent cell surface expression with CD3 and preT alpha (invariant chain)

Pre -B Cell Stage (Transcription)

Expression of pre-BCR in association with CD79a/CD79b heterodimer (pre-BCR complex) Pre-BCR: Two mu heavy chains paired with two pseudo light chains (don't have V, J segments). CD20 is expressed from here to the end of development (Somatic recombination of the light chain variable region occurs here)

Describe and explain the molecular mechanisms involved in the generation of antibody diversity.

Exquisite specificity (and hence diversity) is made possible because the V, D, and J gene segments, which encode the variable regions, are present as multiple germline genes that are rearranged to make unique variable regions. The construction of unique variable regions is referred to as somatic recombination. (multiple germline genes, combinatorial diversity, junctional diversity, random selection/association of light and heavy chains).

FOXP3 Mutation

FOXP3 is a transcription factor that is essential for the development and function of regulatory T cells and mutation leads to IPEX, a multi organ autoimmune inflammatory disease state. Immune dysregulation Poly endocrinopathy Enteropathy X linked syndrome (Presents with watery diarrhea, exema and type 1 diabetes)

Papin cleavage of antibody structure

Fab region: Portion that can bind to the antigen Fc: portion that can be crystalized andd allows the antibody to ineract with other cells. Papain cleaves the disulfide bridge between heavy chains at the hinge region.

Regulatory Proteins that are unique to the alternative pathway

Factor H: Binds to C3b in the fuid phase preventing C3b from binding to the cell surface of microbes. When the C3 convertase has formed, Factor H competitively binds to C3b displacing Bb

Regulatory Proteins that are common to both pathways

Factors I: Cleaves C4b or C3b (bound or soluble) to their inactive form Cb4i and Cb3i in the presence of one of several factors. Decay Accelerating Factor (DAF) CD55: Binds to membrane bound C4b and C3b blocking the formation of the alternative and classical pathway C3 convertases. When the C3 convertases have already formed DAF competitively binds with C3b or C4b promoting their dissociation Anaphylatoxin Inhibitor (AI): Inhibits C3a, C4a and C5a from binding to receptors on mast cells and basophils

Since the number of fluorescent molecules that can be bound to the primary antibody is limited, direct immunofluorescence is substantially less sensitive than indirect immunofluorescence and may result in ______________.

False negatives

T/F: 1 antigen can only have 1 antigenic determinant

False, Antigens may contain several different antigenic determinants.

Fc and Hinge regions

Fc regions (constant): Allow for interaction of immune complexes with other cells Hinge regions: Allows for antibody flexibility, rich in Cysteine and Proline residues.

What experimental proof of negative selection exists?

Female mice do not express H-Y Ag and express CD8 T cells against H-Y Ag; Male mice express H-Y Ag (self-Ag) which leads to elimination of TCR that are reactive against this Ag, and males do not express CD8 T cells against H-Y Ag; requires self-Ag and self-MHC

In Erythroblastosis fetalis, The fetus expressed ___ and the mother expresses ____.

Fetus: Rh + Mother: Rh -

Explain why fibrinogen is present in plasma but not present in serum. Name 4 substances that are anti-coagulants and explain their role when added to tubes in which blood is collected.

Fibrinogen is present in plasma but not serum because plasma contains all the components of the coagulation system (tubes contain anti-coagulant) while serum does not so clotting occurs and consumes fibrinogen. Citrate, Oxalate, and EDTA are all anti-coagulants. Coagulation requires Ca++ and they bind Ca++ preventing blood from coagulating in their presence. Heparin is also an anti-coagulant and it increases the activity of antithrombin

What is the rationale for performing flow cytometry and explain the role that fluorescent probes have in flow cytometry.

Flow cytometry is a useful tool for analyzing molecules on cells that are in suspension. Antibodies to which a fluorescent probe has been attached are incubated with the cells. The scattered light and emitted fluorescent probe light are converted to signals that can be stored in the computer for analysis.

Lineage Determination (Thymic Cortex Process)

Following screening/selection of the thymocytes, there is a transition from double positive thymocytes (CD4+, CD8+) to single positive thymocytes expressing either CD4 or CD8, but not both. Silencing of either the CD4 or the CD8 gene occurs in each individual T cell. T cell lineages are thus classified by their expression of CD4 or CD8, reflective of subsequent biological activity. The function of the T cell is determined at this stage.

Allelic exclusion in somatic recombination

For both alpha and beta chains, successful rearrangement of the DNA on one allele leads to the inhibition of somatic recombination of other allele. (when recombination is unsuccessful on both alleles the cell dies)

What is the first step of the activation of complement via the Classical Pathway?

Formation of antigen-antibody complexes that induce a conformational change in the Fc region of the antibody molecule that exposes a binding site for the first component of complement: C1 component *Other mediators may activate the classical pathway: C reactive protein - CRP binds to phosphorylcholine components of lipopolysaccharides in bacterial and fungal cell walls but not the phosphorylcholine present in the phospholipids of human cell membranes - The C1 binds to CRP, activating the complement cascade

MHC class I

Found on all nucleated cells. Consists of an a chain linked to b2-microglobulin. Binds peptides derived from the intracellular pathway. Displays peptides to TCRs on CD8 cytotoxic T cells.

MHC Class II

Found primarily on dendritic cells, macrophages, and B cells. Consists of an a chain linked to a b chain. Binds peptides derived from the extracellular pathway. Display peptides to TCRs on CD4 T helper cells.

Mast cell/basophil activation

Free IgE Abs (not bound to Ag) bind to high affinity Fcepsilon receptor on mast cells and basophils, sensitizing them. When Ag encountered, crosslinking of IgE-engaged FceR and activation of cell to exocytose its granules Results in vascular permeability, leukocyte recruitment, increased secretion of mucus, increased smooth muscle contraction

What are examples of adjuvant?

Freund's incomplete adjuvant: water in oil emulsion Freund's complete adjuvant: also contains killed mycobacteria

Th2 cells

Fxn: eosinophil recruitment (secretion of IL-5), stimuulation of IgE expression (IL-4 secr.), alternative pathway of macrophage activation (IL-4 and IL-13) Cytokines: IL-4 (mast cells, tissue cells, T-cells) TFs: (GATA-3, STAT6)

Th1 cells

Fxn: kill microbes in phagosomes (CMI) Cytokines: IL-12 (macrophages, DCs), IFN-gamma (NK cells) TFs: T-bet, STAT1/4

Th17 cells

Fxn: recruit other immune cells (neutrophils), stimulation production of anti-microbial peptides called defensins by epithelial cells (IL-17 and IL-22) Cytokines: IL-1, IL-6, IL-23 (all DCs), TGF-beta TFs: RORgamma-t; STAT3

secondary lymphoid tissue associated with the epithelium of the digestive tract - gut

GALT

Non-encapsulated Mucosal Tissues

GALT: Gut associated lymphatic tissue. BALT: bronchus associated lymphatic tissue.. No capsule present. The major antibody produced is IgA from Plasma Cells and offers protection against foreign antigens.

Paroxysmal nocturnal hemoglobinuria (PNH)

GPI (glycosylphosphatidylinositol) linkage not present on red blood cells. Leading to fatigue Shortness of breath and Abdominal pain Red blood cells do not express CD55 and CD59 for protection against complement mediated lysis. Flow cytometric analysis of GPI-anchored proteins (GPIAP) is the gold standard for diagnosis of PNH Treatment: Antibody that binds to C5

VDJ joining

Generation of antigen binding diversity through extensive DNA rearrangement resulting in a unique combination of VDJ DNA regions. Occurs after exposure to antigens. The order of the VDJ segments before recombination is conserved between individuals. The mechanism of recombination is coordinated by *recombinase-activating genes RAG-1 and RAG-2* which recognize specific DNA signal sequences of a heptamer,spacer (12 or 23 bp) and a nonamer recombination signal sequence. *If RAG gene is impaired or missing SCID can arise.*

Splenic Germinal Center

Germinal center contains active B-lymphocytes. Helper T-cells mingle with plasma cells at the periphery of the nodule. PALS are pariarterial sheaths surrounding the central arteriole

how is the progression of gingivitis related to the immune system?

Gingivitis begins with activation of innate immune cells by bacterial products (PAMPs). The development of gingivitis parallels the development of the acute inflammatory response in several ways.

MHC Class I

Glycoprotein expressed on the cell surface of all nucleated cells Presentation of peptide antigen to TC cells

MHC Class II

Glycoprotein expressed on the cell surface of antigen presenting cells Present antigenic peptide to TH cells

CD1 Molecules

Glycoproteins that present lipid and glycolipid antigens to subsets of T cells. They are structurally similar to Class I MHC in that they form a complex with B2 microglobin. However processing and cell surface presentation of the CD1 antigen complex is similar to that of Class II MHC (occurs in acidified endosome). Presentation is to the NKT (Five members CD1a, CD1b, CD1c, CD1d, CD1e and dendritic cells express all.)

why do gram negative bacteria stimulate an immune response?

Gram-negative lipopolysaccharide (LPS) is a potent PAMP! Lipid A is a ligand for many types of PRRs Gram-negative and Gram-positive bacteria modify their cell wall components with amine-containing substituents (shown in red). Some Gram-negative bacteria (e.g., Salmonella enterica) modify their lipid A phosphate groups with phosphoethanolamine and aminoarabinose. Additionally, glycerophospholipids modified with amino acids, such as lysine, represent major membrane lipids in Gram-positive bacteria (e.g., S. aureus). Gram-positives can further modify lipoteichoic acids and wall teichoic acids with d-alanine. The addition of amine-containing substituents to these cell wall components helps decrease the overall negative charge of the bacterial cell wall and protects the bacterium against attack by CAMPs.

main classes of leukocytes in the blood

Granulocytes, lymphocytes, and monocytes

Specify three isotypes of (a) human and (b) murine MHC-class I molecules and the cells that express these molecules.

H2-K, H2-D & H2-L Class I MHC molecules are the three isotypes in mice and are the equivalents of HLA-B, HLA-C & HLA-A Class I MHC molecules isotopes in man (these are co-dominantly expressed and also polymorphic. An individual can possess up to 6 different HLA Class I molecules on their cells)

______ - mouse version of MHC complex

H2-complex

HIV Therapy

HAART RTI, integrase inhibitor, protease inhibitor

_____: Patients produce antibody against the mouse monoclonal antibodies that were injected as therapeutic agent. Symptoms and response is similar to serum sickness

HAMA (human anti-mouse antibody response)

_____ - Human Leukocyte Antigen; human version of MHC complex

HLA

HSC-inducing environment

HSCs and progenitors differentiate/mature on a mesh-like scaffold of stromal cells (fat, endothelial, fibroblasts, macrophages)

______ - all alleles in a gene complex that are inherited together

Haplotype

Define Hapten, Carrier Molecule and Carrier Effect

Hapten: small molecules Carrier Molecule: Large molecule that hapten binds to Carrier Effect: When haptens are coupled to carrier molecules leading to them becoming immunogenic (Haptens are chemicals or degradation products)

Appendix

Have lots of goblet cells and lymphoid follicles (usually active with germinal centers). acute corners in which inflammation can occur due to entrapped debris leading to appendicitis.

____ is the mediator of Mast Cells

Histamine

discuss MHC and immune responsiveness 2) Hole-in-the-repertoire model

Hole-in-the-repertoire model - TCR that recognize different foreign AG may be eliminated during thymic processing b/c closely resembled to self-Ag

Name the immunodeficiency disorder that results from a mutation in CD40L.

Hyper IgM syndrome which results in no switching of isotypes

20.1 Discuss immune responses that prevent virus infection, specifically the role of: IFN-alpha, beta, gamma

IFN-alpha, IFN-beta, NK cells -virus infected cells produce Type I INF that binds to INF-alpha receptor of IFN-beta receptor -initiates JAK-STAT pathway leading RNAse L activation which degrades mRNA -induces dsRNA-dependent protein kinase that inactivates proteins synthesis thereby blocking viral replication IFN-gamma mitogenic stimulation of lymphocytes increases MHC II expression on APC increases antiviral potential of macrophages IFN-beta treatment ofMS

_______ inhibits the expansion of TH2 populations while ____ and ___ inhibit the expansion of TH1 populations.

IFN-gamma IL-4 and IL-10

Cytokines include:

IFN-gamma, TNF-B, IL-2, GM-CSF, MIF

The cytokines released by TH1: The chemokines released by TH1:

IFN-gamma, TNF-beta, IL-2, GM-CSF, MIF IL-8/CXCL*, MCP-1/CCL2

IL-18 made by macrophages + IL-12= stimulates TH1 cells to secrete more _____, that in turn recruits and activates more macrophages *This self-perpetuating response may be a beneficial and protective response or it may be a detrimental response and cause extensive damage to tissues

IFN-γ

Interferons

IFN: glycoproteins that respond to viral infections; shuts down infected cells & stops spread

IFNy on (a) NADPH oxidase, on (b) iNOS, (d) on Th2 cytokines, on (e) Class II MHC expression, and on (f) Class I MHC expression.

IFNy enhances NADPH oxidase activity and induces iNOS activation Down regulates Th2 cytokines and polarizes differentiation of THO to Th1 Role in differentiation of pCTL to CTL (with IL-2) Upregulates MHC Class I on nucleated cells; Class II on antigen presenting cells

Specify the cytokine that polarizes the Th0 cell to that of a Th1 phenotype and the two sources of that cytokine.

IFNy is the cytokine that polarizes ThO cell to a Th1 phenotype and it is secreted by NK cells and also Th1 cells

T cell type 2 cytokines

IL 4 the most important, dont need to know the others

IL-12, IL-15 and IL-18 (Cytokine Secreted by Macrophages)

IL-12: Activates NK cells to secrete IFNγ IL-15 & IL-18: Enhances secretion of IFNγ induced by IL-12

What secretes IL-18 and IL-15

IL-18: Secreted by monocytes, macrophages and dendritic cells and some non immune cells IL-15: Secreted by non lymphoid tissues like epithelial cells and fibroblasts and by activated monocytes/macrophages and dendritic cells (IL-2 and IL-15 share many in vitro biological activities and both signal via CD132 and CD122. IL-12/IL-18 leads to a greater amount of IFNy than IL-12/IL-15 interaction

IL-2 on (a) T cells, (b) [high] on NK cells, (c) pCTL clonal expansion.

IL-2 enhances activation of T cells expressing IL-2R In high concentrations it causes NK cells to become LAK and defend the body against tumors Role in differentiation of pre-CTL to CTL (with IFNy)

Proliferation and differentiation of activated T cells (in context of IL-2)

IL-2 mRNA is inherently unstable; signaling from activation stabilizes, upregulates TFs for gene tx, and increases IL-2 production; activated T cells also rapidly upregulate expression and increase affinity of IL-2R

What defects can cause SCID?

IL-2 receptor (subunit-gamma) JAK3 (important signaling molecule) ADA IL7R-alpha chain CD3-delta chain RAG1 or RAG2 deficiency Artemis deficiency (gene encoding DNA repair recombination enzyme)

Describe the role of IL-3, IL-5 and IL-7 in hematopoiesis

IL-3: Role in differentiation of a pluripotent stem cell to a lymphoid progenitor and myeloid progenitor along with GM-CSF IL-5: Differentiation of a myeloid progenitor to eosinophil (good for helminth protection) IL-7: Role in differentiation of a lymphoid progenitor to B cell progenitor, T cell progenitor and NK cell (produced in the thymus)

What cytokine plays an important role in class switching?

IL-4

Name two cytokines released from basophils and mast cells.

IL-4 and IL-5 FcεRII (CD23b) requires IL-4 to be expressed on T-cells, monocytes, Langerhans cells, eosinophils, and macrophages)

Specify the cytokine that polarizes the Th0 cell to that of a Th2 phenotype and the most likely source of that cytokine

IL-4 is the cytokine that polarizes the ThO cell to a Th2 phenotype and the most likely source is a mast cell

Chemokines include:

IL-8/CXCL*, MCP-1/CCL2

Mast cell mediators in Type I hypersensitivity

IMMEDIATE: vasoactive amines (histamine; pre-formed) proteases (preformed; tissue damage) Prostaglandins (rapid de novo synth); vasodilation Leukotrienes (rapid de novo synthesis); smc contraction LATE PHASE REACTIONS: (~4hrs) cyto/chemokines (TNFa, IL-4/5); influx of Th2 cells, eosinophils, neutrophils, basophils

Discuss the immuno receptor tyrosine-based activation motif (ITAM) of CD3 in a signal transduction

ITAM is a cytoplasmic domain of all CD3 chains involved in signal transduction; conserved sequence of 4 amino acids repeated twice

Define idiotype and idiotopes

Idiotype: The collection of idiotopes in a given antibody Idiotopes: antigenic determinants in hypervariable regions (Antibodies generated to the collection of idiotopes on a single antibody molecule are termed anti-idiotypic antibodies)

Cross-presentation of viral antigens by DCs

If DCs are not infected by virus, the viral antigens must be obtained through an extracellular source (typically by phagocytosis of an infected cell). In this case, viral antigens are processed and presented by both the extracellular AND intracellular pathways to ensure activation of CD4 and CD8 T cells. Activation of CD8 T cells by antigen obtained by phagocytosis is called cross-presentation.

If immune complexes aren't cleared effectively, they may ____

If immune complexes aren't cleared effectively, they may deposit in tissues - May trigger release of inflammatory mediators and vasoactive mediators - Proteases released may damage connective tissues - Clots may form as complexes activate platelets - Symptoms include fever, rashes, joint pain, lymph node enlargement, and protein in the urine -- Vasculitis if in blood vessel -- Glomerulonephritis if in kidney -- Arthritis if in joints

Explain the conditions leading to a false negative result (VDRL Test)

If the patient's serum is not diluted and antibodies are in excess this will lead to a false negative

What type of Ig has a secretory component?

IgA

predominant secretry Ig - milk, saliva, tears, mucus exist as dimers or tetramers

IgA

Which Ig is present in mucus secretions?

IgA (also in milk, saliva, tears-- this is the predominant secretory Ig)

What type of Ig has a J chain?

IgA and IgM

What minor variations have been observed in sub-isotypes to further classification?

IgA1, IgA2 IgG1, IgG2, IgG3, IgG4

together with IgM, this class is the major membrane-bound Ig expressed by mature B cells

IgD

___ specific for Der p1 binds and triggers mast-cell degranulation.

IgE

binds to Fc receptors on basophils and mast cells, induces degranulation of basophils and mast cells

IgE

Worm cytotoxicity

IgE Abs coat worm and engage high affinity Fcepsilon receptors on eosinophils, leading to worm-directe exocytosis of eosinophil granules w/ release of toxic cationic proteins to kill the worm

Compare the half-life of circulating IgE with that of bound IgE.

IgE antibodies bound to FcεR1 have longer half life (weeks to months) than circulating IgE (less than 24 hours). (Bound IgE antibodies are now available for binding antigens specific for their FAB region.)

Type 1 Hypersensitivity

IgE mediated hypersensitivity Ex: Allergies

Maternal ___ antibody crosses placenta and destroys fetal blood cells- results may be minor or lethal

IgG

most abundant class, with four subtypes that are distinguished from one another by the size of the hinge region and the number and position of inter-chain disulfide bonds between the heavy chains

IgG -IgG1, IgG3, IgG4 are important in protecting the developing fetus

Opsonization

IgG Abs bind microbe, Fc region binds FcgammaR of macrophages or PMNs...phagocytoses

Antibody-dependent cellular cytotoxicity (ADCC)

IgG Abs bind microbial antigens or tumor antigens; crosslink Fcgamma receptor molecules on NK cells (CD16) to induce apoptosis of target cell

Which Igs contain a hinge region and which do not?

IgG, IgD, and IgA contain hinge regions that are flexible and give the possibility of changing angle of the two Fab arms no hinge region in IgE or IgM, the CH2 domain replaces the hinge region

less efficient as potent complement activator

IgG1, IgG2

binds with high affinity to Fc receptor

IgG1, IgG3

cross placenta, protects developing fetus

IgG1, IgG3, IgG4

binds with low affinity to Fc receptor

IgG2

potent complement activator

IgG3

binds with intermediate affinity to Fc receptor

IgG4

not a complement activator

IgG4

Which Ig class develops first in the primary response?

IgM

accounts for 5-10% of all Ig, monomeric are expressed as membrane-bound receptors in B-cells that are naive secretes as pentameric first Ig to be synthesized in primary response and in newborn

IgM

What class of surface Ig is/are present on naive B cells?

IgM and IgD

Coexpression of IgM and IgD alternative splicing

IgM is ONLY expressed by IMMATURE B cells (In bone marrow). MATURE B CELLS express both IgM and IgD in circulation.

Why is IgM better at activating complement than IgG?

IgM requires only a single antigen-bound molecule for C1 activation; a high density of IgG on the antigen is required for close proximity of two IgG Fcs this is why complement activation by IgM plays an essential role in defense against encapsulated bacteruia

Plasma cells

IgM: short lived; in spleen and lymph nodes for days IgG: pre-plasma cells home to, and undergo terminal differentiation, in bone marrow; produce most of IgG found in blood IgE: plasma cells home to submucosa and skin IgA: mucosal tissues

Mature B Cells

Immature B Cells that survive tolerance induction in the bone marrow migrate to the spleen to complete maturation Alternative splicing of hnRNA leads to cell surface co expression of IgM and IgD (naive B Cells) CD40 is expressed during transition from immature to mature B cell stage (Mature B Cells circulate and migrate to other secondary lymphoid tissues)

Discuss negative selection and the experimental proof for negative selection

Immature B cells that express auto-Ab against self-reactive Ag are eliminated in the bone marrow (clonal deletion) H2d/k transgenic mouse lacks IgM Ab specific for Hdk because B cell with anti-H2k binds to self-Ag Class I MHC so H2k is present on stromal cell of H2d/k transgenic mice and self-reactive B cell is eliminated Self-reactive B cells can be saved from apoptosis by heavy chain associating with different light chains (light chain editing)

Specify the distribution of dendritic cells and how it enables them to be "gate-keeper" in peripheral tissues.

Immature dendritic cells are present in all lymphoid and non lymphoid tissue except the brain. In the skin epidermis they are called langerhans cells. They function as gate keepers in peripheral tissue where they capture antigens and carry them to secondary lymphoid tissues and present them to CD4+ T cells. Some immature dendritic cells are also resident in secondary lymphoid tissues where they capture antigens that have invaded that site. (when they endocytose antigens they become mature)

Dendritic Cell Cytokine Secretion

Immature dendritic cells express receptors for chemokines that direct them to appropriate secondary lymphoid tissue following their encounter with antigen (during this migration they undergo further differentiation) In secondary lymphoid tissues (primary immune response site) dendritic cells present the antigen to T cells and secrete cytokines (IL-12, IL-15, IL-18 and IL-23)

Type 3 Hypersensitivity

Immune Complexes of Antigen and Antibody Ex: Serum sickness

Type III hypersensitivity is mediated by ___

Immune complex

Function of spleen

Immune surveillance and response in BLOOD. Collects antigens in blood and also degrades old RBCs and damaged RBCs.

what is autoimmune disease and how common is it?

Immune system can react to almost anthing (adaptive) btu sometimes goes overboard = autoimmune disase 80% pop has this now, and is increasing, very relevent to dentistry

Define Immunofixation and name two cancers that result in high concentrations of abnormal monoclonal antibodies or paraproteins?

Immunofixation: A confirmatory test for multiple myeloma based on antigen-antibody interaction (identifies monoclonal antibodies) High concentrations of paraproteins are found in Multiple Myeloma and in Waldenstrom macroglobulinemia (cancers)

__________ or ________ rely on the use of antibodies to label a specific target antigen with a fluorescent dye (also called fluorophores or fluorochromes) such as fluorescein isothiocyanate (FITC). Antibodies that are chemically conjugated to fluorophores are commonly used in IF. The fluorophore allows visualization of the target distribution in the sample under a fluorescent microscope.

Immunofluorescence (IF) or cell imaging techniques

How may IF be applied?

Immunofluorescence can be used on tissue sections, cultured cell lines, or individual cells, and may be used to analyze the distribution of proteins, glycans, and small biological and non-biological molecules. Immunofluoresence can be used in combination with other, non-antibody methods of fluorescent staining, for example, use of DAPI to label DNA.

Explain the conditions required to generate a precipitate.

Immunoprecipitation is based on the interaction of antibodies and soluble antigens to form immune complexes (lattice). 1) Antibody must be bivalent or polyvalent to allow interaction of at least two antibody molecules. 2) Visible precipitation, a requirement for laboratory tests, relies on the relevant concentration of antigen and antibody. When the ratio of antibody to antigen is appropriate, visible precipitation will result (zone of equivalence)

IgE

Important for allergic reactions-Type I hypersensitivity reactions. Binds to FCepsilon receptors on Mast cells that induces degranulation, secretion of histamine, heparin into the blood stream. Ecosanoids and cytokines also released. Also found in high levels in parasitic infections. Important in asthma response due to mast cell leukotiene release.

Nitric Oxide

Important for the elimination of intracellular organisms that are resistant to ROIs and lysosomal enzymes in the phagolysosomes. NO targets iron sulfur proteins in the organisms transport chain inibiting their respiratory cycle. It also inhibits key enzymes of DNA synthesis Synthesis of NO requires the induction of inducible nitric oxide synthase (iNOS) which catalyzes the conversion of Arginine to Citrulline and NO in the presence of oxygen (NO gas is extremely toxic to the phagocytes and host tissue at high levels. It has a short half-life which limits its damage)

T cell initiation of primary adaptive immune responses

In a primary adaptive response, naïve T cells are activated by antigen presentation by dendritic cells that have captured antigen and migrated to secondary lymphoid tissues.

which are more prevalent in the blood, lymphocytes or monocytes? What do they look like?

In blood, lymphocytes are more prevalent than monocytes Blood monocytes (A) can be distinguished by their "horseshoe" shaped nuclei and relatively large cytosolic area compared to lymphocytes (B), which possess a concentric-shaped nucleus and minimal cytosol.

What is the distinguishing feature of multiple myeloma proteins regarding specificity and isotype?

In multiple myeloma all the plasma cells secrete antibody of the same specificity (all bind the same epitope) and isotype. Therefore, the myeloma can be classified by the antibody paraprotein isotype.

DC maturation

In response to microbes, DCs (stimulate cytokine production) undergo (change in phenotype) maturation and migrate to secondary lymphoid tissues (able to present antigens). In response to microbes (PAMPs), DCs develop a mature phenotype- low phagocytic ability but potent antigen presenting ability:

Define Reverse Passive agglutination

In reverse passive agglutination assays the RBCs are coated with known antibodies and then used to detect the antigens in the test sample serum.

Define passive agglutination

In the indirect agglutination test, known soluble antigens are coated on to other cells (e.g., sheep or turkey erythrocytes) which act as passive carriers of antigens and will associate with antibodies specific to the antigens.

In the initiation phase of Type IV...

In the initial phase of antigen contact, TH cells proliferate and differentiate into TH1 cells.

Monoclonal Antibodies as therapeutic agents

In theory, the intravenous injection of monoclonal antibodies should provide the long sought magic bullet for cancer or autoimmune therapy but the efficacy of monoclonal antibody therapy is limited by many factors.

How do free antigens and DCs play a role in immunity?

In tissues, free antigens and DCs that capture antigens migrate to a draining lymph node to stimulate a primary adaptive response.

Immunodeficiency or Hyporeactivity

Inability to recognize and control health-threatening agents leading to an absence of immune function or specific immune response. Causes can be congenital or acquired, due to senescence, iatrogenic, due to malnutrition, malignancies or infectious organisms, or due to trauma or stress.

Specify the source, phenotype and role of a/i Tregs

Include CD4+, CD25+ and FOXP3+ and arise in the periphery following activation of ThO cells in the presence of TGFB (transforming growth factor beta) and absence of IL-6 They control immune responses to both foreign and self antigens by down regulating effector CD4+ and CD8+ T cells (Do the same job as nTregs but are produced peripherally instead of centrally)

Secondary Lymphoid Tissues

Include lymph nodes, tonsils, adenoids, spleen and mucosa associated lymphoid tissue (MALT). Both B cells and T cells are found in discrete areas of these tissues as well as dendritic cells and macrophages. (Major sites of adaptive immune responses with the site of the initial immune response being determined by by the antigens mode of entry.)

Physiologic barrier

Includes *body temperature, low pH, chemical mediators, lysozymes, complement system, lactoferin* (breast milk and skin secretion-inhibits bacterial growth), low stomach pH. All of these factors work to inhibit bacterial growth and prevent entry into the body.

Phagocytic Cells

Includes Neutrophils, eosinophils, monocytes, and specialized tissue macrophages. Involved with phagocytosis of foreign moelcules/pathogens, cell recruitment via molecular mediators, and presentation of peptide antigens to lymphocytes. *Monocytes are blood circulating phagocytes (circulate for 1-3 days)* before migrating to tissue to *become a macrophage.* Tissue Specialized macrophages and dendritic cells: in the brain (microglia) lungs (alveolar macrophages) liver (Kupffer cells) kidneys (mesangial cells) bones (osteoclasts) gastrointestinal tract (peritoneal macrophages). Lymph nodes (dendritic cells) Skin (Langerhan's cells) CNS (Glial Cells)

C-type lectin receptors.

Includes the mannose receptor that bind mannan-containing glycoproteins, which triggers endocytosis or phagocytosis.

Discuss HLA and disease susceptibility

Individuals with HLA allele for a certain disease compared to same allele in general population determines relative risk of disease; homozygous for MHC makes more susceptible to disease; if risk=1, then no association between allele and disease; if risk>1, then possible association

T dependent Antigens (Monoclonal Activator)

Induce naive B cell activation only when interaction with CD4+ T cells and cytokines derived from the T cells are available to the B cell (Most are large, complex proteins)

Mucosa-associated lymphoid tissues (MALT)

Inductive sites are sites where antigen is first encountered and the primary immune response takes place. *Tonsils and Peyer's patches are permanent lymphoid structures and are NOT encapsulated*. Do NOT have afferent lymphatics. Effector sites are diffuse sites where specific immune cells can respond to antigen immediately. Includes: lymphatic nodules, laminapropria in nasal passages, intestinal tract and intraepithelial lymphocytes.

_____ promote priming of TH2 cells that drive IgE responses

Inhaled allergens: - Molecular type: Proteins - Function: proteases - low dose: favors activation of IL-4 - low mol wt: easily diffuses into mucus - high solubility: allergen is readily eluted - high stability: can survive as particle - contains peptide that bind to host MHC class II for T-cell priming

discuss the inheritance pattern of HLA haplotype in a typical family

Inherit one HLA haplotype from each parent (ex. Haplotype AC includes all the alleles from A and all alleles from C)

What are the inhibitors of the Classical Pathway?

Inhibitors: (1) C1 inhibitor: Soluble regulator of the classical pathway that competitively inhibits the protease activity of C1 until enough is produced to overwhelm the inhibitory effect *C1INH is name of protein (2) C3 convertase inhibitors: Factor I: cleaves C4b to prevent C3 convertase Decay accelerating factor (DAF): has ability to dissociate C3 convertase

What are the inhibitors of the Alternative Pathway?

Inhibitors: C3 convertase inhibitors: - Following proteins bind to Cb3 to prevent association with factor B, and is then cleaved by factor I ---- Complement receptor type 1 (CR1) ---- Membrane cofactor protein (MCP) ---- Factor H - Decay accelerating factor (DAF): has ability to dissociate C3 convertase ** Saialic acid residues present on the surface of mammalian cells inactivates C3b

What is the P-K reaction?

Injected serum from allergic individual intradermally into non-allergic individual. Later injection of allergen to same site as serum caused reddening and swelling. "A local skin reaction to an allergen by a normal subject at the site of injected IgE from an allergic individual"

how are the innate and adaptive immune responses related?

Innate cells initiate adaptive immune responses by the process of antigen presentation.

which type of immune response acts first?

Innate immunity is the first-line defense against microbial pathogens and is carried out by mechanisms that exist before an infection.

2.16 (2) Compare innate immunity vs adaptive immunity. Response Time Specificity Response to repeat infection

Innate response: -hours to respond -limited and fixed -identical response to repeat infection as primary response Adaptive response: -days to respond -highly diverse, improves during the course of immune response -much more rapid response to repeat infection than primary response

Define Agglutination

Interaction between antibody and a particulate antigen resulting in visible clumping; requires polyvalent antigen

Discuss cytokine involvement in proliferation and class switching during the differentiation of B cells into plasma cells

Interaction of CD40L/CD40R releases an array of cytokines that result in plasma cells with different Ig isotypes depending on the cytokines released · Proliferation: IL-2, IL-4, IL-5 · Differentiation: IL-2, IL-4, IL-5, IFN-γ, TGF-β

_____ - trimeric protein that interacts in binding cleft to prevent endogenous peptides from binding to Class II; transports Class II MHC to endocytic vesicles

Invariant chain

Type II Hypersensitivity involves what? What are examples?

Involves antibody-mediated destruction of cells Examples: - ABO-blood group incompatibilities - Hemolytic disease of the newborn - aka erythroblastosis fetalis - Drug induced hemolytic anemia - such as penicillin-induced

Severe Combined ImmunoDeficiency (JAK3)

JAK3, presents clinically the same as those with CD132 mutation, however occurs in both males and females Lack of signaling via receptors for IL-2, IL-4, IL-7, IL9, IL-15, & IL-21. All these cytokine receptors signal via JAK3. Therefore, a defect in JAK 3 leads to same as a defect in CD132 Treatment: Bone Marrow Transplant or IVIG

NK cell direct recognition receptors

KAR (Killer Activation Receptors): allow NK cells to recognize viral peptides embedded in the surface of virally infected cells KIR (Killer Inhibitory Receptors): Allow the NK cell to recognize self healthy cells and ignore them. This prevents normal cells from being destroyed -recognize Class I MHC and self peptides (NK activation is regulated by integration of signals from KARs and KIRs)

elements and organization of the immune system (summary)

KNOW THIS

4.7 (2) Discuss the experimental approach using haptens in the demonstration of specificity of the immune system.

Karl Landsteiner's work demonstrated the specificity of antibody and the enormous diversity of epitopes the immune system is capable of recognizing Injection material: Hapten (DNP) Carrier (BSA) Hapten-carrier mixture (not conjugated) Hapten-carrier conjugate Antibodies produced: none anti-BSA anti-BSA maximum amount of anti-DNP, minimum amount of anti-BSA and anti-DNP/BSA combo In this experiment, aniline was hapten. Antisera were raised against different forms of aniline. Each antiserum reacted only with its specific hapten. Showed even a small structural perturbation can be specifically recognized by immune symstem.

What experimental proof of positive selection exists?

Knockout mice were deficient in either Class I or II MHC and subsequently were found to not have CD8 and CD4 respectively (absence prevents positive selection)

X-linked severe combined immunodeficiency

Lack of T and NK cells, decr. cell-mediated and humoral immunity Genetic cause: mutation in gene encoding cytokine receptor common gamma chain (IL-2,4,7,13,15,21 all share this chain) lack of IL-7 = defective T cell maturation (req'd for survival/expansion of early T cell progenitos in thymus) lack of humoral immunity = no T cell help lack of IL-15 = no NK cells

What is the late stage of T cell maturation in the thymus?

Late Phase - proliferation stops; α-chain rearrangement because RAG1/2 present; DP TCR cell undergoes positive and negative selection; cells that survive selection develop into immature single positive cells (CD4 or CD8), then undergo more negative selection and migrate from cortex to medulla then to circulation as mature T cells

When testing a patient for Hashimoto's thyroiditis, what antigen is bound to latex particles? What is the auto antibody in Hashimoto's thyroiditis?

Latex particles coated with the antigen thyroglobulin are used to detect anti-thyroglobulin antibodies in serum from patients with this autoimmune disorder.

hematopoiesis (what is it, where does it occur, when, and what regulates it)?

Leukocytes arise by the process of hematopoiesis, which begins with undifferentiated pluripotent stem cells in the bone marrow. Hematopoiesis occurs throughout life and is regulated by cytokines.

Light chain Loci

Light chains are encoded by two separate loci, a Kappa and Lambda, on two different chromosomes which contain only V and J segments. Light chain rearrangement occurs AFTER heavy chain rearrangement. Failure of kappa rearrangement results in a backup of lambda rearrangement.

How are pamps and damps different?

Like PAMPs, DAMPs are recognized by PRRs, but unlike PAMPs they arise endogenously.

Dendritic and macrophage cells as antigen presenting cells

Like dendritic cells macrophages also express CD4 and the chemokine receptors CCR5 and or CXR4. Consequently, macrophages can readily be infected with HIV-1. Furthermore, the constitutive expression of Class II MHC and costimulatory molecules is rather low in these cells.

______ - actual diversity is less than expected; certain allelic combinations exist more frequently in HLA haplotypes than predicted by random combination. Causes: too few generations in human population to allow enough crossover; haplotypes are over-represented so reflect founder population; selective pressure with disease prevalence

Linkage disequilibrium

Typical Manifestations of Type III?

Localized Arthrus reactions and generalized reactions such as serum sickness, necrotizing vasculitis, glomerulonephritis, rheumatoid arthritis, and systemic erythematosus **Symptoms include fever, rashes, joint pain, lymph node enlargement, and protein in the urine

Lymph Nodes

Located along the lymphatic channels throughout the body. Consists of an outer cortex (location of primary and secondary follicles), paracortex and medulla Afferent Lymphatics: Penetrate the connective tissue that encapsulates the lymph node and empty their contents into the sub-capsular sinuses. Sinuses: Lined with tiny holes that allow lymph and its contents to seep through the lymph node and come in contact with lymphocytes. They also allow lymph to reach efferent lymphatics.

Immunoglobulin heavy chains

Located on Chr 14 in gemline configuration in all cells except B cells. B cells have multiple gene segments which are rearranged during devo: Variable (V) diversity (D) Joining (J) and Constant (C).

Progression of Ab response to infection

Low levels of transient low affinity/high avidity IgM-->IgG, IgA, or IgE and memory B cells (incr at 1 week, peak at 4 weeks post-infection) serum Ab levels then drop to and persist at intermediate levels for years

IgG

Lowest molecular weight and has high affinity and can cross maternal placenta. Has both anti-viral and anti-bacterial activity. 3 roles of IgG: Neutralization Opsonization Complement activation Most common Isotype is IgG1

Direction of lymph flow

Lymph vessels have one way valves that prevent backflow of lymph fluid.

where does lymph/lymphatic fluid come from?

Lymphatic fluid or lymph arises from normal leakage of fluid from blood capillaries caused by hydrostatic and other forces. Lymph enters the lymphatic system via afferent lymphatic vessels and exits lymph nodes via efferent vessels that eventually form the thoracic duct, which returns lymphatic fluid to the bloodstream.

cellular effectors of the adaptive immune system

Lymphocytes (Cell-mediated Immunity)

alternative splicing

M1 and M2 exons encode transmembrane and intracytoplasmic domains of IgM; if splicing occurs in site 1, these exons are lost and secreted form is produced; if splicing occurs at site 2, membrane-bound form is produced

Regulatory Proteins that are unique to the Common/Terminal Pathway ( inhibitors of the membrane attack complex)

MAC inhibitors (MAC INH): Inhibit formation of MAC on autologous cells. S-protein (vitronectin): binds to soluble C7 complexes preventing their insertion into autologous (Self) membrane . HRF20: bind to C8, preventing the formation of MAC. CD59 (Protectin) : Prevents the final assembly of MAC via C8 and C9

Secretory IgA in the intestinal lumen

MALT IgA is secreted as dimeric IgA by plasma cells in the lamina propria. Transport to the lumen is initiated when it binds to a protein (Secretory component) on epithelial cells. Attached IgA and secretory component is endocytosed and transported through epithelial cell in a vesicle and when it reaches the lumen the SC is cleaved with the IgA keeping a small part of it (D-IgA-SC) -SC protects it from degradation D-IgA-SC is called secretory IgA and it functions in immunosurveillance binding to organisms before they bind to M cells. Aggregated IgA activates the alternative pathway of complement system (neutralizes pathogens)

What are the roles of Major Basic Protein (MBP) and Eosinophil Cationic Protein (ECP) in defense against heminths?

MBP: Disrupts membranes of parasite ECP: Forms pores in the parasite's memrane

____ - complex of genes encoding cell surface molecules involved in self-non-self recognition Ag presentation to T cells

MHC

MHC Class I - structure, function, and genomic organization

MHC Class I - on cancer/virus-infected cells; glycoproteins expressed on the surface of all nucleated cells to present antigens to TC cells; α1 and α2 responsible for forming the peptide-binding cleft; α3 highly conserved and interacts with CD8 on TC cells. β2 microglobulin expressed on cell surface; if none of these molecules, then no expression of Class I molecules

Describe the role and cell expression, properties of MHC class I molecules.

MHC Class I molecules are cell surface glycoproteins that play a critical role in conveying the presence of infected cells in the body. The message is transmitted to CD8+ T cells when infected cells display foreign peptides in the groove of MHC-Class 1 The cells that present antigen peptides are referred to as target cells because the antigen displayed on their surface with MHC 1 targets them for CD8+ T cell mediated death. All nucleated cells contain MHC I molecules and MHC I molecules only binds peptides from endogenous sources

MHC Class II - structure, function, and genomic organization

MHC Class II - glycoproteins expressed on the cell surface of APCs; two polypeptides as dimer (α and β chains); present antigens to TH cells

MHC Class III - structure, function, and genomic organization

MHC Class III - various secreted proteins functioning in immune response like complement and inflammation

MHC inheritance patterns

MHC class I is inherited from mom and MHC class II is inherited from dad. Since an individual gains one strand of DNA from each parent, most people have two distinct variants of A, B and C for a total of 6 distinct MHC I genes.

List other surface molecules expressed by B cells

MHC class II molecules (allows B cell to be APC) CR1, CR2 (receptors for certain complement components) FcyRII (receptor for antibody) B7 (interacts with T-cell molecules) CD40 (interacts with T-cells)

7.1 H2-complex

MHC of moue, codes proteins either directly performing or associated with antigen presentation to T lymphocytes

Describe positive selection

MHC restriction; in cortex of thymus with thymocytes and cortical epithelial cells interacting; only cells whose αβ recognize/bind self-MHC survive and rest apoptosis; during Late Phase [Eliminate non-self]

TCR antigen binding

MHCs bound to an APC will present an antigen held in it's peptide groove to the TCR CDR.

Live attenuated (weakened) vaccines

MMR, chickenpox, rotavirus contraindicated for T-cell immunodeficient individuals

Cytokines Released by TH1 Cells Recruit ____ What does this lead to? (effector phase)

Macrophages In fully developed DTH, only 5% of the cells are antigen-specific TH1 cells and the remainder are macrophages and other nonspecific cells. TH1 cells release IL-3 and GM-CSF that induces hematopoiesis of graulocyte-monocyte lineage of cells. IFN-γ and TNF-β (plus macrophage derived TNF−α and IL-1) induce changes in nearby endothelial cells causing them to express adhesion molecules so that leukocytes can adhere and move. Monocytes are attracted to the site by monocyte chemotactic factor (MCP-1/CCL2) at 24-48 hours and become terminally differentiated into macrophages. Cytokine-macrophage inhibitory factor (MIF) secreted by TH1 cells prevent macrophages from migrating beyond the DTH reaction site.

Monocytes

Macrophages that ingest and destroy bacteria by expressing receptors specific to many bacterial constituients (Mannose receptor, TLRs, Glucan receptors, CD11b and CD18, and LPS receptor CD14). Phagocytosis forms phagosome which fuses with lysosome (phagolysome). Monocyte activation results in secretion of interferons, lysosyme, and cytokines which help mediate immune cell communication and regulation.

IL-12

Main cell source: DCs, macrophages Effect/target: NK cells: increases interferon gamma and cytotoxicity

IL-10

Main cell source: Macrophages, T cells Effect/target: Suppresses immune system

Type I IFN (IFN alpha or beta)

Main cell source: Macrophages/fibroblasts Effect/target: increase anti-viral state, activate NK cells

IFN-gamma

Main cell source: NK cells/T cells Effect/target: Macrophage activation, increases antibody responses

IL-6

Main cell source: macrophages Effect/target: fever, liver acute phase proteins

IL-1

Main cell source: macrophages Effect/target: activates endothelial cells, neutrophils, causes fever, weight loss

IL-8, i.e. chemokines

Main cell source: many cells Effect/target: leukocyte activation, chemotaxis, increases affinity for adhesion molecules

Tumor necrosis factor (TNF)

Main cell source: Macrophages, T cells Effect/target: activates endothelial cells, neutrophils, causes fever, weight loss

MHCs

Major Histocompatibility Molecules MHC molecules are heterodimeric proteins that bind antigenic peptides non-specifically.

MHC

Major histocompatibility complex is a highly polymorphic (Allotypic polymorphism ) locus on a chromosome comprised of multiple genes encoding histocompatibility antigens that play critical roles in recognition of "self" vs. "non-self" and regulation of interactions among immune system cells such that antigen presentation on MHC molecules results in activation of adaptive immune responses. Particular MHC alleles are associated with better protection against infectious disease.

Compliment Receptors

Many cells have receptors for the proteolytically derived complement fragments and this dictates which cells respond to complement activation. Compliment Receptors include: CR1, CR2, CR3a/4a, CR5a

Tonsil distribution

Many germinal centers, and M cells also present within tonsils.

where do infections most often occur?

Many microbes (normal flora/commensals) are opportunistic. Anywhere wet membranes occur = barriers to infection that is suceptible, especially GI tract as it is supposed to absorb things

Treatment of Type I Hypersensitivity:

Mast cells express both FcεR1 (activating) and FcγRIIB (inhibiting) Ig receptors If a cell binds IgE and IgG, the inhibiting signal induced by IgG binding wins out This is partially why inducing IgG in atopic individuals (usually through "allergy shots") helps treat their allergies

Type II Hypersensitivity- Erythroblastosis fetalis

Maternal IgG antibody crosses placenta and destroys fetal blood cells. Fetus expressed Rh + antigen on its blood cells; mother's are negative. 1st pregnancy: Rh- mother may conceive baby with Rh+ father and baby inherits father's Rh +. At delivery, mother is exposed to to Rh + cells via umbilical cord blood and develops anti Rh antibody (IgM) and memory cells against Rh factor. Each pregnancy after, with a Rh+ baby, mother will develop anti Rh antibodies and Erythroblastosis fetalis (fetal hemolytic anemia) will occur.

B lymphocytes

Mature in bone marrow and produce antibodies to fight bacterial infections; part of the humoral immune response; B cells circulate in the blood, lymph, and lymphoid organs

T lymphocytes

Mature in thymus and express TCR recognizing Ag on MHC -T helper and T cytotoxic cells

mature phenotype

Mature phenotype Increased mobility (migrate to lymph nodes or spleen!) Decreased activity of PRRs High expression of co-stimulatory molecules (B7, CD40, MHC Class II)

Erythrocyte sedimentation rate (ESR, sed rate)

Measure of time it takes for erythrocytes to form sediment in vitro. Elevated during infection due to increased protein, interaction with charges on RBCs and rouleaux formation (coin stacking). Increased ESR facilitates neutrophil migration by allowing extra time for PMNs to interact with adhesion molecules during diapedesis.

What is the mechanism of Type II hypersensitivity?

Mechanism - IgG or IgM mediated, cytotoxic - Cell destruction via classical complement or anti-body dependent cell cytotoxicity (ADCC)

Discuss the TCR rearrangement

Mechanism is similar to that of Ig rearrangement; 12/23 rule, V(D)J recombinase with RAG1/2, TdT N-nucleotide addition to all TCR junctions (unlike just heavy of Ig), double-strand break repair enzymes (ligases, exo/endonucleases), alternative joining of D segments, junctional flexibility NO SOMATIC MUTATION

What is the mechanism of Type I hypersensitivity?

Mechanism: Allergen exposure causes TH2 B-cell response leading to IgE production * Remember IL-4 is the cytokine (produced by TH2 cells) that gives the communication to class switch to IgE from mast cell/basophiles and TH2 cells. - IgE binds to mast cells (or basophils) via Fc∑1 or Fc∑II(Pretend ∑ is an epsilon) which sensitizes the mast cells (or basophils). - Once enough IgE present on mast cells/basophils, second exposure causes mast cell/baso activation and acute allergic rxn. IgE cross-linking on mast cells/baso which leads to degranulation and release of vasoactive amines *required pre-sensitization*

What is Type I hypersensitivity mediated by?

Mediated by IgE antibodies and interaction between the IgE and multivalent antigen * Recall that IgE responses are mounted against parasitic infections

What is the process that takes place within the MAC

Membrane Attack Complex (MAC)= C5 convertase - C5b binds to C6 and C7 to form a heterotrimer complex --- The C5b67 complex inserts into the phospholipid bilayer of the target cell; if this reaction takes place on an immune complex, then C5b67 is released ---> insert into membrane of nearby cell and mediate "innocent bystander" lysis *Regulator proteins prevent this from happening - Complex then binds C8; the heterotetramer (C5b-C6-C7-C8) then inserts itself into the membrane creating a small pore (enough to lyse RBCs but not nucleated cells.) this heterotetramer then recruits C9 to form large pores in the target cell membrane ---> Cell lysis due to water and electrolyte loss

Secondary response of adaptive immunity

Memory of previously encountered antigens results in a faster and greater immune response upon subsequent antigen exposure.

Explain why macrophages are not as effective as antigen presenting cells as dendritic cells

Microphages are not as effective as antigen presenting cells as dendritic cells especially in primary immune response because unlike secondary immune responses, primary immune responses occur in secondary lymphoid tissues and dendritic cells act as gatekeepers which capture antigens in the periphery and transport them to secondary lymphoid tissue for destruction.

Clonal expansion

Mitotic division of cells after clonal selection occurs - clone selected for specific antigen - has job to do, so now it multiplies; B cells with specific Ig bind to specific Ag; Ag-activated B cells undergo clonal expansion; allows for B cell differentiation into clones of many memory and plasma cells

PAMPs

Molecules associated with microbes, usually containing repeated structures, that activate innate cells.

Chemokines

Molecules that induce leukocyte accumulation in tissues at sites of inflammation. They contribute to both innate and adaptive immune processes. The presence or absence of chemokines determine the course of the immune response to a pathogen. (Chemokines and C5a are chemoattractants because they attract cells to a particular region.)

How are monoclonal antibodies generated?

Monoclonal antibodies are generated from immunized animals. Single cell suspensions from the spleen of immunized animals are fused with myeloma cells, this forms hybridomas, which are both immortal and secrete the antibodies of interest. Hybridomas are then screened to detect the relevant antibodies. Reactivity is determined in enzyme-linked immunosorbent assays (ELISAs), looking for plate-bound antibody. Once the hybridoma cells of interest have been identified, they are sub-cultured to serve as antibody factories that secrete the appropriate monoclonal antibody.

Monoclonal Antibodies vs Polyclonal Antibodies

Monoclonal:Collection of antibody molecules arising from a single clone of antibody secreting plasma cells, all of which recognize the same, and only one, epitope on the immunizing antigen. Polyclonal: The total antibody collection from all the different clones

what immune cells are phagocytic?

Monocytes, macrophages, dendritic cells, and neutrophils are the major phagocytes of the innate immune system

Describe basic structure of monomeric antibody. Specify three forms other than monomeric

Monomeric Antibody :Two identical light chains covalently linked to two identical heavy chains. Each of these have a variable region. There are also dimeric, trimeric and pentameric forms of Igs

Specify the HLA allele that is expressed in most patients with Ankylosing Spondylitis.

Most people with ankylosing spondylitis test positive for HLA-B27

AIRE Mutations

Mutations in AIRE protein can result in a range of autoimmune disorders especially of the endocrine system. Autoimmune Poly Endocrinopathy Candidiasis Ectodermal Dystrophy (APECED)

Bruton's Tyrosine Kinase (Btk)

Mutations in the Btk are associated with X-linked agammaglobulinemia (XLA) Btk plays a critical role in B cell activation, differentiation and proliferation. Initial block occurs at the pro-B to pre-B cell transition. Pre-B cells that form are defective and so maturation is halted at this point

_____ : prolonged infected macrophages fuse to form multinucleated giant cells that release of high concentrations of lytic enzymes which destroy surrounding cells (the "double-edged sword" nature of DTH)

Mycobacterium tuberculosis

DTH rxns are induced by a variety of intracellular pathogens such as...

Mycobacterium tuberculosis (bacteria). Candida albicans (fungus), Leishmania (protozoa), and Herpes virus. *** Can be caused by contact antigens such as poison ivy, hair dye, and cosmetics.

Describe the immune processes that led to the binding of Fcγ to the target cell. Describe also how the target cell is destroyed (Indirect Recognition)

NK cells express FcγR receptors that interact with Fcγ that is bound to a target cell (non specific). Different antibodies recognize different viral proteins embedded in the cell membrane of an infected cell and then kill it. This process is known as antibody dependent cell mediated cytotoxicity (ADCC)

Describe natural killer (NK) cells with respect to: differentiation and sites where they are normally found

Natural killer cells arise from bone marrow precursors (lymphoid progenitor cell) and are found in the blood, spleen and peritoneal exudate. (5-15% of circulating lymphocytes) NK cells kill cells that are stressed and infected and also kills some tumor cells following conjugate formation with the target cell. (conjugate formation of NK cells lead to the release of lytic molecules that contain perforin and granzymes that destroy the target cells)

Mitogens (Polyclonal Activator)

Naturally occurring molecules that have the capacity to bind to and trigger proliferation of many clones of lymphocytes. (B cell mitogens include pokeweed and high concentrations of LPS.)

key study ideas for T cell activation and differentiation

Naïve CD4 and CD8 T cells are activated (or primed) by dendritic cells in secondary lymphoid tissues. T cell activation leads to clonal proliferation and differentiation into effector T cells or memory T cells and requires antigen presentation (Signal 1), CD28/B7 co-stimulation (Signal 2), and cytokines(Signal 3). Naïve CD4 T cells differentiate into Th1, Th2, or Th17 subsets in response to cytokines produced by APCs and other cell types. Effector T cells and memory T cells are activated by antigen presentation at the site of infection.

Discuss the process of T cell activation

Naïve T cells scan surface of APCs to find Ag (in peripheral lymphoid organs, leads to expansion/differentiation of T cells to effector or memory cells); Activation of TH cells begins with interaction between TCR-CD3 and MHC-peptide, leads to expression of immediate (transcription factors), early (interleukins), and late genes (adhesion molecules); the actual TH cell activation occurs when CD28 interacts with B7 family; inhibition occurs when CTLA-4 (CD152) on active T cell interacts with B7 on APC

CD4+ Thp Cells

Naïve T cells that will undergo antigen-induced differentiation in a secondary lymphoid organ following initial encounter with antigenic peptide-MHC class II. The role that they play in host immunity occurs only after this antigen-induced differentiation.

CD8+ pCTL Cells

Naïve T cells that will undergo antigen-induced differentiation in the periphery following initial encounter with antigenic peptide-MHC class I. These cells will differentiate to mature cytotoxic cells whose role is to destroy infected autologous cells and some tumor cells

Describe negative selection

Negative selection - self-tolerance; results from interaction of thymocytes with dendritic cells and macrophages (having MHC); thymocytes with TCR with high affinity for self-Ag plus self-MHC or self-MHC alone are eliminated by apoptosis; result is that T cells are self-tolerant in that they won't respond to self-Ag

Describe negative selection in the medulla and how it differs from that occurring in the cortex.

Negative selection within the medulla is accordingly more finely-tuned than in the cortex, with multiple high avidity interactions, including TCR, CD4 (CD8) and class II (class I) MHC products all playing prominent roles.

Negative Signalling in B cells and B cell and Plasma Cell Down Regulation

Negative signalling refers to inhibition of B cells following antigen induced activation. This occurs when secreted IgG cross links the membrane bound antibodies with the integral membrane receptor FcyRIIB. This interaction decreases BLyS receptor levels

Specify infection susceptibility if proteins in the terminal pathway are mutated or deficient

Neisseria sp infections

Neutrophil migration and Diapedesis

Neutrophils crossing endothelium via reversible binding, activation, adherence, and movement between endothelial cells.

Neutrophils (PMNLs) (phagocyte)

Neutrophils differentiate from precursor cells in bone marrow with more than a billion being created a day, they comprise up to 60% of the circulating leukocytes in peripheral blood and have a half-life of 8 hours. Chemotactic factors that attract them to the site of inflammation include IL-8/CXCL8 and C5a generated in the early phase of inflammatory response (Their numbers increase in the circulation in response to bacterial infection - neutrophilia)

neutrophil activation/weak binding

Neutrophils first undergo "weak binding" or tethering to the vessel surface, then "roll" along the vessel where they are activated by chemokines (CXCL8).

diapedesis

Neutrophils then squeeze through pores between adjacent endothelial cells

binding of what cells is critical for T cell proliferation?

No CD28 (on T cell) - B7 (on antigen presenting cell) binding = no T cell proliferation (tolerance)!

How is Type I hypersens. induced?

Non-parasitic antigens induce a humoral response resulting predominantly in IgE production. Fc∑ receptors on the surface of mast cells and basophils bind IgE and are sensitized when coated with IgE Upon second exposure with antigen, these cells rapidly degranulate= local or systemic vasodilation and smooth muscle contraction

_____ - express Class II for a short period of time; fibroblasts, glial cells, pancreatic β cells

Non-professional APCs

Discuss the non-peptide antigen of T cells

Non-protein infectious agent presented to T cells by non-classical Class I MHC (CD1); Ag could be lipids or glycolipids

Innate Immunity

Non-specific first line of defense mechanism present before any exposure to pathogens effective from birth. It consists of external barriers like the skin and mucus membrane and internal chemical defenses that destroy infectious agents that breach the external barrier (Rapid host protection without memory or specificity. Innate immunity also produces cytokines and chemokines.)

Basophil

Not common in blood (lowest percentage). *Involved in Type I hypersensitivity* responses. *High affinity for IgE* which binding to it causes degranulation of active mediators: histamine, prostaglandins, leukotrienes.

IgD

Not found in significant amounts. Important in *Initial antigen triggering of B cells* while *bound to the membrane surface of the B cells*, NOT SECRETED antibody. Found in the bone mmarrow

Primary follicles and germinal centers of lymph nodes

Note the different sites of localization between T and B lymphs. T cells are found in the marginal mantle area whereas B cells congregate in the germinal centers.

Chronic graft rejection

Occurs after months to years narrowing of blood vessels (arteriosclerosis); alloreactive T cells secreting cytokines and alloreactive antibodies

Superantigens (Oligoclonal Activators)

Often bacterial products and activate subsets of T cells. Bind specifically to VB regions of the T cell (200 VB shared by entire T cell population) This binding triggers the activation of all the clones that express given VB which leads to clonal expansion of many clones (oligoclonal)

Role of CD4+ T Cells in B cell activation

Once Class II MHC/peptide is displayed on the B Cell surface after antigen recognition and processing, it is recognized by the activated CD4+ T cells. This results in a T cell/B cell conjugate that is stabilized by adhesion molecules (I-CAM-I/LFA1 and LFA-3/CD2) B7/CD28 and CD40/CD40 Ligands also interact as B cell costimulatory signals

T/F each pathway of complement activation has its own effector mechanisms

Once activated, the effector mechanisms are the same for each pathway!

How are opsonins generated?

Opsonins are the products of: 1) Complement Activation (C3b) 2) B Cell Activation (Fcy-IgG) 3) Cytokine Mediated Activation of Hepatocytes via IL-6 (CRPs) (Interactions of any of these pathogen bound opsonins trigger phagocytosis)

Optivo and Yervoy

Optivo® (blocks PD-1) and Yervoy® (blocks CTLA-4) are monoclonal antibodies that enhance T cell activation and are approved for lung cancer and melanoma, respectively.

Chemotaxis

Organized movement by phagocytes towards microbes along concentration gradients of chemotactic factors. Surface receptors on phagocytes respond to chemotactic factors like complement breakdown product C5a and Muramyl Dipeptide (MDP) a bacteria product

The route allergen takes, site of immune complex deposition, and resulting disease.

Other types: - Autoimmune diseases: lupus, Rheumatoid arthritis, Goodpasture's syndrome - Drug interactions: allergies to penicillins and sulfonamides - Infectious diseases: post-Strep A glomerulonephritis, meningitis, mono, malaria, trypanosomiasis - Human anti-mouse antibody response (HAMA): patients produce antibody against mouse monoclonal antibodies that were injected as therapeutic agent, caused serum sickness

How was Type I hypersens. discovered?

P-K Reaction

How was Type I discovered?

P-K Reaction "A local skin reaction to an allergen by a normal subject at the site of injected IgE from an allergic individual"

vocal to study

PAMPS, Pattern recognition receptors Toll-like receptors Mannose receptors Defensins Proinflammatory cytokines IL-1 TNF NF kappa B Type I interferons Antiviral response Reactive oxygen species Respiratory burst CXCL8 Neutrophil rolling Diapedesis Selectins Integrins Alternative pathway C3 convertase Anaphylatoxins Opsonins Membrane attack complex

wah stimulates Expression of B7 on the surface of the APC?

PAMPs

Pathogen Associated Molecular Patterns (PAMPs) vs Danger Associated Molecules (DAMPs)

PAMPs: molecules expressing the molecular patterns on pathogens (Muramyl Dipeptide, bacterial or viral DNA) recognized by PPRs DAMPs: Molecules originating from dying or damaged cells or other biological molecules that bind to PRRs (uric acid crystals, cholesterol crystals)

Identify the two subsets of T cells on which PD1 is expressed. Describe PD1 and the type of signal that the cell receives when PD1 is engaged with its ligands (PD1 = Programmed Cell Death 1)

PD1 is a transmembrane protein expressed on activated CD4+ and CD8+ T cells. Interaction of PD1 with PDL1 and PDL2 delivers a negative signal to T cells limiting their activation and immune mediated tissue damage.

Name the two ligands for PD1 and the cells on which they are expressed.

PDL1 ligand is constitutively expressed on a number of immune cells and non hematopoietic parenchymal cells (heart, lung, colon, brain) PDL2 ligand expression is limited to activated monocytes and dendritic cells

How do we prevent Erythroblastosis fetalis?

PREVENTION Anti-Rh antibodies are injected into mother at 28 weeks of pregnancy or within 24 - 48 hours after delivery. The antibody (i) binds to fetal red blood cells that may have entered the mother's circulation and (ii )facilitates fetal rbc clearance (clears out Rh+ cells) before B-cell activation. The anti-Rh antibodies are marketed under the name Rhogam.

Pattern Recognition Receptors

PRRs - phagocytes recognize common structural motifs that are highly conserved~PAMs (eg. peptidoglycan in Gram pos bacteria is a PAM) ex. -CD14 (LPS receptor) -Toll-like receptors (TLRs)~intra or extracellular -mannose receptors -secreted receptors

Non-MHC ass'd autoimmune disease

PTPN22: RA NOD2: Chrohn's IL23R: IBD, Psoriasis, AS CTLA4: DM1, RA CD25: MS, DM I

When testing a patient for Rheumatoid arthritis, what antigen is attached to the latex particles? What is the auto antibody in this autoimmune disorder?

Particles coated with IgG (bound via Fab to expose Fc region) are used to detect rheumatoid factor The antigen is an IgG antibody, the target for rheumatoid factor which is the auto antibody in this disorder.

What is the difference between passive agglutination and reverse passive agglutination?

Passive agglutination is a test used to detect antibodies in the patient's serum that will bind antigen on the modified particle. Particles (e.g. latex, tanned red blood cells) are coated in vitro with antigen (e.g. thyroglobulin). Reverse passive agglutination is a test used to detect antigen in a patient's sample. It is similar to passive agglutination; an antibody coats the particle (typically latex beads)

HAMA (human anti-mouse antibody response):

Patients produce antibody against the mouse monoclonal antibodies that were injected as therapeutic agent. Symptoms and response is similar to serum sickness.

Innate immune mechanisms of gingivitis

Penetration of the gingival epithelial barrier by bacteria. Activation of resident macrophages by PAMPs leading to production of IL-1, TNF-a, and chemokines (CXCL8). Transmigration of neutrophils from blood capillaries into the subepithelial region. Activation of neutrophils by PAMPs leading to secretion of proteolytic enzymes and production of ROS. Activation of complement generates anaphylatoxins (C3a, C5a).

Discuss the experiment demonstrating that antigen recognition by T helper cells is MHC Class II restricted

Peritoneal macrophages incubated with Ag and Ag-pulsed macrophages incubated with T cells; degree of T cell proliferation was measured; strain-2 macrophages activated strain-2 and F1 T cells but not strain-13 T cells; confirmed that CD4+ TH cell activates and proliferates only in presence of Ag-pulsed macrophages that share class II MHC alleles (restricted)

Define Peyer's Patches and M cells

Peyer's Patches: Organized aggregates of follicles present in the GALT located in the ileum of the small intestines. M Cells: Specialized epithelial cells present in the mucosal luminal lining that allow the entry of microbes into MALT to reach the underlying lamina propria which is the site of follicles and immune cells (phagocytes, dentritic cells and lymphocytes)

cellular effectors of the innate immune system

Phagocytes Natural killer cells Epithelial cells

Antigen-antibody (immune) complexes are usually cleared by _____

Phagocytic cells

how is phagocytosis important to the immune response?

Phagocytosis delivers microbes to intracellular compartments and is accompanied by production toxic molecules The microbe enclosed by the phagocyte membrane (phagosome) enters the cell and fuses with lysosomes forming a phagolysosome. The microbe is killed in the phagolysosome by proteolytic enzymes, reactive oxygen species (ROS), and nitric oxide (NO).

Phases of a clinical trial

Phase I - few subjects; assess safety and efficacy Phase II - high risk individuals and patients suffering from disease; assess efficacy against disease Phase III - many subjects; assess efficacy

BLyS (B Cell Stimulator)

Plays a critical role in B cell selection and survival. Monocytes/Macrophages, Dendritic Cells and some lymphocytes produce BLyS and it is first expressed as a cell surface protein Upon cell activation its cleavage and release is triggered by cytokines or crosslinking of FcyR by IgG. (leads to B cell survival)

IL-8/CXCL8 (Chemokines Secreted by Activated Macrophages)

Plays a role in the mobilization and chemotaxis of neutrophils to sites of inflammation

Poly vs. Monoclonal antibodies

Polyclonal antibodies are antibodies that have specificities for many epitopes as opposed to only having specificity for just one like a monoclonal antibody.

Explain advantage of polymorphism & co-dominant expression of MHC molecules.

Polymoprhisms increase the likelihood that one of the MHC alleles present in individuals in a population will bind to and present an antigen fragment of any particular microorganism to T cells. Class II molecules HLA-DP, HLA-DQ and HLA-DR are co-dominantly expressed on all APCs. Meaning that there is a minimum of 6 different class II molecules will be expressed on the cell surface ( We express the HLA molecules we get from both parents. Polymorphisms basically increases the variability of MHC molecules and this is an advantage for survival)

_____ - many alternative forms of alleles exist at each locus

Polymorphism

Describe positive selection

Positive selection - MHC restriction; in cortex of thymus with thymocytes and cortical epithelial cells interacting; only cells whose αβ recognize/bind self-MHC survive and rest apoptosis; during Late Phase

Single positive thymocytes

Positively selected CD4 or CD8 T cells arriving in the thymic medulla are screened again to make sure they are not autoreactive. (interactive avidity of T cells with antigen presenting cells include interaction of CD4 and CD8 with MHC at this stage)

What are pre-B cells receptor?

Pre-B cell receptor - membrane bound μ heavy chain associates with surrogate light chain and Ig-α/Ig-β heterodimer; only cells with Pre-B receptor complex proceed to further development to then rearrange light chains to increase diversity

Discuss stromal microenvironments, surface molecules and cytokines relevant to pre-B cell development

Pre-B cell starts expressing IL-7 receptor (and down regulates adhesion molecules) that binds to IL-7 on stromal cell to then detach and divide/differentiate; no direct contact with stromal cell

Describe the classical precipitation curve in terms of: equivalence

Precipitate forms *Point of graph depicting max precipitate formation

Primary vs Secondary Follicles

Primary Follicles: Contain predominantly mature resting B cells and no germinal centers Secondary Follicles: Contain germinal center of antigen activated B cells. (Both types of follicles contain B cells, macrophages, dendritic cell and follicular dendritic cells. The regions in between the follicles contain T cells interspersed with dendritic cells.)

Name the two types of tissues of the immune system and their function

Primary Immune Tissue: Include the bone marrow and thymus and serve as developmental sites for lymphocytes. Secondary Immune Tissue: Inculde the lymph nodes, spleen, and mucosa associated lymphoid tissues and serve as activation sites for lymphocytes (B cells are produced in the bone marrow and stay there until maturity. T cells are produced in the bone marrow and transported to thymus where they mature)

IgM

Primary antibody in response to challenge. most efficient for complement fixation. Efficient for bacterial and viral agglutination, isohemaglutinin that is naturally present with A and B blood groups.

Primary vs. Secondary humoral response

Primary: -long lag phase -low magnitude of Abs -short duration Secondary: -short lag phase -higher magnitude of Abs -longer duration (months)

What are the differences between primary and secondary humoral responses?

Primary: Primarily secretes IgM Lag phase (slow) B cells undergo clonal expansion and differentiation into plasma and memory cells Secondary: Secretes primarily IgG Response much faster Antibodies have higher affinity for antigen- due to somatic hypermutation and class switching

Compare primary and secondary humoral responses:

Primary antibody response vs. secondary

Primary: more IgM than IgG; as antigen-specific memory B cells are generated in primary response, secondary response is IgG dominant, with some IgA

immature phenotype (DCs)

Prior to exposure to foreign substances, DCs have an immature phenotype- high ability to capture and process antigens but poor ability to stimulate T cells: DCs possess an immature phenotype (able to capture antigens) in a non-inflammatory environment. Immature phenotype Low mobility (stay put!) High expression and activity of PRRs (e.g.; mannose receptors) Low expression of co-stimulatory molecules (B7 (CD 80 and 86), CD40, MHC Class II)

Discuss the role of the stromal microenvironments in progenitor B cell development

Pro-B cell directly contacts stromal cell (bone marrow) to mature to Pre-B cell; VLA-4 on Pro-B interacts with its ligand VCAM-1 on stromal cell to adhere then Pro-B expresses c-kit (tyrosine kinase) that combines with stem cell factor (SCF) to activate c-kit and differentiate to Pre-B (complete heavy chain rearrangement)

List the cell surface molecules present during the Pro-B and Pre-B stages of B cell development

Pro-B: c-kit, CD45R, CD19, CD24, Ig-α/Ig-β, IL-7R, CD43 Pre-B: CD45R, CD19, CD24, Ig-α/Ig-β, IL-7R, CD25

List the cell surface molecules present during different stages of B cell development

Pro-B: c-kit, CD45R, CD19, CD24, Ig-α/Ig-β, IL-7R, CD43 Pre-B: CD45R, CD19, CD24, Ig-α/Ig-β, IL-7R, CD25

B Cell differentiation/Activation

Process by which antigen encounter, in the presence of appropriate T cell, leads to clonal expansion, isotype switching, affinity maturation (somatic mutation), differentiation to antibody secreting plasma cells, and memory B cell formation. (Primary encounter with antigen occurs in secondary lymphoid tissues producing primary immune responses)

IgA

Produced by mucosal cells esp in the GI system. *Has a J-chain and secretory component allowing corss over from basolateral side of epi cell to the lumen.* First line defense of mucosal surfaces and is *bactericidal for Gram negs in the presence of lysozymes.* Efficient bacterial and viral agglutinator and plays a important role in passive immunity passed from mother to baby in breast milk. IgA has a secretory component that is able to cross epithelial basal lamina propria out into the lumen.

____ - cells that present Ag to CD4 and have co-stimulatory activity; macrophages, B cells, dendritic cells

Professional APCs

___ arise from fetal liver and adult bone marrow and migrate to thymus - cells are called thymocytes

Progenitor T cells

hinge region

Proline rich region, very flexible; change angle of two Fab arms; present in all but M or E

_____ - protein complex that degrades Ub-tagged proteins by hydrolyzing peptide bonds

Proteasome

Rh Antingens

Proteins expressed on the surface of red blood cells. About 85% of humans express this antigen on their red blood cells. (Clinically significant is the potential for Rh incompatibility between an Rh- mother and a Rh+ fetus.)

How do the allergy shots work?

Pts allergic to a particular allergen can have the severity of symptoms reduced to varying degrees by giving repeated subcutaneous injections of increasing doses of the allergen. The purpose is to shift Ig production from IgE to IgG. IgG competes with IgE for the allergen when it is encountered, binds it and forms IgG-allergen immune complexes that can be eliminated but do not induce Type I hypersensitivity.

Red Blood Cells and their effects on C3b

RBCs have CR1 opsonin receptor so they can bind C3b and transport them to the liver and spleen where phagocytes can remove them and the RBC can be returned back to circulation

2 Methods to Assess Type I Hypersensitivities: 1.________ - Measures Total IgE 2. _______ - Measures Allergen Specific IgE

Radioimmunosorbent test (RIST) Radioallergosorbent (RAST)

What are the reactants involved in the Classical Pathway?

Reactants: C1: - binds to antigen-antibody complexes - composed of 1 C1q, 2 C1r, 2 C1s C1q - subunit that directly binds Fc region of antibodies - must bind to at least two Fc sites on the Ig molecule to be activated C1r - intermediate, regulatory subunit that activates C1s via cleavage of C1s C1s - enzymatic subunit that has two substrates: C2 and C4 - cleaves C4 (= C4a and C4b) -- C4b attaches to the target surface next to the C1 complex -- C2 binds C4b and then C2 is cleaved by neighboring C1s(=C2a and C2b); C2b diffuses away -->production of classical C3 convertase complex (C4bC2a**) C3 convertase (C4bC2a)- hydrolyzes C3 to form C3a and C3b - can generate over 200 molecules of C3b causing AMPLIFICATION -some C3b binds to C4bC2a= C4b2a3b(C5 convertase) and remainder diffuses away to coat immune complexes functioning as an opsonin -- The C3b component of C5 convertase binds to C5 and alters the conformation of C5 --- altered C5 is cleaved by C4bC2a into C5a and C5b --C5a diffuses away and C5b binds to C6 to initiate formation of membrane attack complex (MAC)

What are the reactants of the Alternative Pathway?

Reactants: Once bound to Factor B, the C3b-B complex undergoes a conformational change that exposes binding sites for Factor D which cleaves factor B into Ba and Bb subunits upon binding. Hydrolyzed C3 forms complex with Bb sub-protein to form alternative C3 convertase complex (C3bBb) *** half life of only 5 minutes but is stablized if the serum protein properdin binds it - alternative C3 convertase complex can bind with C3b in the same way as classical and form an alternative C5 convertase [C3bBb + C3b = C3bBbC3b(alternative C5 convertase)] - continues same as classical (--> MAC)

ROS

Reactive oxygen species *Short-lived reactive molecules formed from molecular oxygen that are toxic to microbes and normal cells.

Pattern recognition receptors

Receptors on most cell types, especially phagocytes and epithelial cells, that bind PAMPs and DAMPs resulting in cellular activation.

Pattern Recognition Receptors (PPRs)

Receptors on phagocytes that recognize different molecular patterns on viruses, bacteria, fungi and other human pathogens as well as an assortment of molecules released during tissue damage or stress. PPRs exist as membrane bound receptors, cytosolic receptors or secreted receptors and they trigger cascades of biological events that lead to the secretion of inflammatory cytokines.

Recruitment

Recruitment is regulated by locally produced cytokines (IL-1b and TNFa) and chemokines (CXCL8) secreted by tissue macrophages.

Events of the acute inflammatory response

Recruitment is regulated by locally produced cytokines (IL-1b and TNFa) and chemokines (CXCL8) secreted by tissue macrophages. Blood vessels dilate to increase blood flow to the site of infection (due to histamine and other inflammatory mediators). Neutrophils first undergo "weak binding" or tethering to the vessel surface, then "roll" along the vessel where they are activated by chemokines (CXCL8). Activated neutrophils then undergo "tight binding" or adhesion to the vessel surface where the rolling slows dramatically. Neutrophils then squeeze through pores between adjacent endothelial cells (diapedesis) and migrate to the source of chemokines (chemotactic response)

4 signs of inflammation

Redness (rubor)- due to dialtion of small blood vessels. Swelling (tumor)- Extravascular fluid accumulation (edema) and inflammatory cell migration. Heat (calor)- vascular dilation and increased blood flow (hyperaemia) chemical mediators lead to systemic fever. Pain (dolor)- stretching and distortion of tissues by edema, pus pressure. Chemical mediators (bradykinin, prostaglandins, serotonin).

Explain the role of NK cells during a viral infection and cancer.

Regardless of the mode of interaction with the target cell, conjugate formation of NK cells lead to the release of lytic molecules that contain perforin and granzymes that destroy the target cells. (NK cells destroy the cell before the cytotoxic T cell response is initiated)

Follicle Associated Epithelium (FAE)

Regions where there are no goblet cells and the mucus layer is sparse or absent. M cells also serve as microbial portals of entry in the lamina propria here.

Immunoglobuulin isotype (class) switching

Req interaction of CD40 on follicular B cells w/ CD40L on Tfh cells, as well as Tfh cell-secreted cytokines IFNgamma-->IgG1/3 IL-4-->IgE IL-5/TGFbeta-->IgA

IL-4

Required to switch to IgE, down regulates Th1 cytokines, down regulates iNOS and polarizes ThO differentiation to Th2

Acquired Immunity

Requires *recognition specificity* to foreign, non-self, antigens. Must be *induced b*y other immunoregulatory agents, usually part of the *innate immune system*, to become active against infections or tumors. Properties include: 1.* Antigen-specificity*- recognizes antigens, proteins, carbohydrates, lipids, or nucleic acids. 2. *Memory*- Results in increased reactivity upon repeated antigen or infectious agent exposure. 3. *Regulation*- Discrimination between* self and non-self *to prevent autoimmune reactions.

Indirect Recognition

Requires the deposition of various opsonins to bind to the surface of the pathogen. Once bound, opsonins are recognized by the phagocyte and it binds. (Opsonins: CRP, Fcy (IgG) and CR-1)

Selectins and their role

Rolling adhesion E-selection and P-selectin: found on endothelial cells L-selection: recirculating B- and T-cells

21.1 (4) Bare-lymphocyte syndrome (BAR)

SCID-like deficiency (Type I) -mutation in TAP -defect in Class I MHC processing -deficit in CD8 T cells -susceptibility to viral infections TypeII -class II deficiency- defect in transcriptional factors

Type III HS Diseases

SLE, Polyarteritis nodosa, post-streptococcal glomerulonephritis, serum sickness serum sickness (systemic vasculitis, nephritis, arthritis)

How do virus prolong their stay in host cells?

Sabotaging the expression of the peptide/class I MHC complexes on the cell surface effectively protects the virus and the infected cells can serve as factories and reservoirs for viruses.

Spleen

Secondary lymphoid organ containing white pulp and red pulp. The white pulp contains the majority of the lymphoid cells. Periarterial Lymphatic Sheath (PALS): The predominant T cell region, the white pulp area surrounding the central arteries and arterioles. B cell regions are the primary and secondary follicles that exist as outgrowths of the PALS and the marginal zone contains primarily dendritic cells and macrophages

gene rearrangement

Segments of DNA can move from one location to another in the genome to allow for the generation of different protein products. The synthesis of antibodies takes place gene segments separated by non-coding sequences; VJC for light chain, VDJC for heavy chain; each V segment has a signal/leader peptide at 5' end

_____ - T cells recognize Ag only when presented by a self-MHC molecule; T cell must learn self-MHC to proliferate; Antigen recognition by CD8+ TC cell is Class I MHC restricted; Antigen recognition by CD4+ TH cell is Class II MHC restricted

Self-MHC restriction

Differentiation of monocytes in bone marrow

Self-Renewing Stem Cell > Pluripotent stem cell (Monoblasts)> Myeloid Progenitor > GM Progenitor > Monocyte (enters circulation and differentiates into macrophages)

Type III Systemic Hypersensitivity: ______ Notable for the presence of hemorrhage in skin, fever, weakness, generalized vasculitis (rashes) with edema and erythema, lymphoadenopathy and sometimes glomerulonephritis

Serum Sickness

Specify the role of thymic epithelial cells

Serve as antigen presenting cells expressing MHC Class I/self peptide or MHC Class II/self peptide for thymocyte TCR to scrutinize

Immature B Cell Stage

Shift from pre-BCR to BCR via assembly of somatically rearranged light chains and heavy chains with CD79a/CD79b. (BCR is expressed on the surface and pre-BCR is down regulated) Specific inactivation of B cells expressing autoreactive mIg is accomplished by apoptosis or non responsiveness here ( This stage is marked by tolerance induction)

what does signal 1 stimulate?

Signal 1 initiates T cell proliferation! The TCR Complex contains a TCR, CD3, zeta chain, and CD4 or CD8. CD3 and zeta chains contain ITAMs (immunoreceptor tyrosine based activation motifs) needed for signal transduction. without ITAMs there would be no signal. Binding of MHC/peptide to the TCR activates Lck! Immunological synapse- antigen presenting cell binding to T cell is what xxx (36)?

what stimulates CD40L expression?

Signal 1 stimulates expression of CD40 ligand (CD40L) on T cells!

2 signal requirement for T cell activation

Signal 1: TCR recognizes specific antigen presented in MHC context; CD4/8 coreceptors increase avidity of Signal 1 (SPECIFICITY) Signal 2: CD28 on T cell binds B7 on DC; T cell will upregulate surface CD28 when it first interacts/is becoming activated to maximize activation process (GUARDS AGAINST AUTOIMMUNITY)

Discuss the two signals that are necessary for T cell activation

Signal 1: interaction of TCR-CD3 to MHC-peptide Signal 2: after Signal 1, antigen non-specific signal provided by interaction between CD28 on T cells and B7 family of receptors of APC (activation here)

what does signal 2 do?

Signal 2 sustains signal 1 leading to production of IL-2 (T cell growth factor) Resting T cells express the low-affinity IL-2 receptor (two subunits b and gc). Signal 2 stimulates production of a chain, which combines with b and gc to form the high-affinity IL-2 receptor (abg). High-affinity IL-2Rabgc can bind IL-2 to stimulate T cell proliferation. IL-2 was originally called T cell growth factor. Production of IL-2 is inhibited by the drug cyclosporine. is autocrine?

Lymph node CORTEX

Site of activity of lymphocytes.

Cytokines (Interleukins)

Small peptides secreted by activated leukocytes which stimulate and regulate aspects of the immune response and haematopoiesis. Different cytokines may trigger the same biological response (functional redundancy). Cytokines are pleitropic and each one can mediate numerous seemingly unrelated biological effects. They are also synergistic (combine) and are critical for all aspects of immunity

Define Agglutination inhibition

Soluble antigen in patient sample is mixed with antibody (reagent). Antigen-particulate is added. Outcome: No agglutination= positive reaction Agglutination= negative reaction

Recombinant cytokine inhibitiors

Soluble receptors are made by fusing extracellular part of receptor w/ Fc region of IgG (which has a high half life in blood); binds cytokine to prevent it binding to normal receptors on cells

T cell repertoire

Somatic recombination and diversification can create a repertoire of millions of different TCRs which can give rise to a unique T cell clone. There may be as many as 25,000 identical TCRs on any given cell and collectively the clones expressing the receptors represent the T cell repertoire

The fate of memory B cells

Some memory B cells colonize the secondary lymphoid tissues. However, most join the pool of recirculating B cells that circulate from blood, lymph, and tissues that were the primary sites of previous antigen encounter. Entry of memory B cells into lymph nodes occurs via afferent lymphatics rather than HEVs because memory B cells have reduced expression of L-selectin, molecule that facilitates extravasation of naïve B cells from the blood to the lymph node at the HEVs.

Discuss the classic experiment by Zinkernagel and Doherty demonstrating MHC restriction by cytotoxic T cells

Spleen cells were mixed with intracellular 51Cr-labeled target cells of: uninfected H-2K, infected H-2K and infected H-2b; killing of the target cell by TC assessed by 51Cr in the medium; demonstrated MHC restriction by TC cells

IL-23 (Cytokine Secreted by Macrophages)

Stabilization of Th17 cells during differentiation from Thp cells (requires TGFβ, IL-1/IL-6 and IL-21) (Elevated in multiple sclerosis, psoriasis and crohn's and is also a proinflammatory cytokine)

Stages of B Cell development

Stem cell--> proB cell--> Pre-B cell--> immature B cell--> mature B cell (if activated by antigen then progresses to)--> Memory B cell or Plasma Cell.

What was the experiment showing the existence of cell-mediated immune response?

Strain C receives graft from strain A Strain C rejects graft in 10-14 days If the same strain C receives a second graft from strain A, rejection is faster (can occur in 4-8 days this time) due to secondary response

In general terms define the terms "subclass" and allotype as it relates to IgG and IgA

Subclass: IgG and IgA variation (small differences in AA sequences in heavy chain constant region) (IgG1, IgG2, IgG3, IgG4 and IgA1, IgA2). These different subclasses have different biological activities and different half lives. Allotype: Polymorphisms within IgA or IgG constant region (Am and Gm)

Antigen

Substances capable of reacting with preformed antibodies or activatable cells (specific portions of substances that have high specificity for antibody binding sites).

Discuss T cell activation by super-antigens

Superantigens - bacterial/viral proteins bind to Vβ-domains of TCR and α-chains of Class II MHC that crosslink and activate massive amounts of TH and secretion of cytokines by TH leading to systemic toxicity (can be exogenous or endogenous)

Be able to identify what H2-Kk is. (i.e. what's the anchor)

Superscript letter represents allele type. The big letter represents the gene locus (anchor).

Name 5 disorders for which the anti-nuclear antibodies (ANA) may be detected

Systemic Lupus Erythematosus Rheumatoid arthritis, Juvenile chronic arthritis Drug-induced lupus Hashimoto's thyroiditis Graves' disease

Typical manifestations: IgE mediated allergic responses:

Systemic and local anaphylaxis

what initiates T cell activation?

T cell activation is initiated when a peptide/MHC complex on the APC binds to a specific TCR.

T cell antigens

T cell antigens are peptide antigens and can only activate T cells through the process of antigen presentation!

Discuss the role of T helper cells in the B cell response

T cell interaction: · TCR recognizes MHC-peptide · CD28 on activated TH interacts with B7 on B cell · CD40L of TH interacts with CD40 on B cell that induces expression of cytokines supporting proliferation of mature B cells

MHC restriction

T cell receptors can only recognize a peptide antigen if it is presented by an APC bearing host MHC molecules.

overview of antigen presentation by T cells

T cells are activated by the process of antigen presentation. Antigen presentation is the process by which antigenic peptides are displayed on the surface of antigen presenting cells (APCs) for recognition by T cell receptors. T cell antigens are peptide antigens and can only activate T cells through the process of antigen presentation! Depending on the route of antigen capture, antigenic peptides are loaded onto MHC Class I or II molecules inside the cell, and the MHC/peptide complex is displayed on the APC surface. T cell activation is initiated when a peptide/MHC complex on the APC binds to a specific TCR.

Types of T cells

T helper lymphocytes -TCR and CD4+ cells recognize exogenous antigen processed and presented by MHC Class II molecules T cytotoxic lymphocytes -TCR and CD8+ cells recognize endogenous antigens processed and presented by MHC Class I molecules

T independent vs T dependent antigens

T independent antigens can only produce IgM however T dependent antigens can produce other classes of Igs via CD40 receptor

Functions of T-lymph response

T-cells express a TCR with specifficity for an antigenic determinant. Regulates immune responses, integral in cell mediated immunity, and critical in B-cell antibody production.

B cell activation (by T-dependent antigens)

T-dependent antigens are soluble proteins or non-protein molecules like carbs attached to proteins activation leads to signal transduction: activation of TFs, endocytosis of antigen, altered gene expression, antigen processing/presentation w/ MHCII; upregulation of Cytokine receptors (CCR7) activated B cell is now an APC for CD4+, which ahve been activated by DCs; Th and APC interactions occur. B cells will now upregulate CXCR5 in response to cytokines from T cells and return to follicle (Now a follicular B cell) w/ Tfh and generate germinal center

T lymphocyte development

T-lymphs develop in the thymus and interact with MHC molecules to determine self vs. non-self differentiation. (auto-recognizing T-lymphs are destroyed).

Discuss self-MHC restriction of T cells

TCR can only recognize self-MHC/specific peptide complex

TCR-CD3

TCR forms complex with CD3 to function in signal transduction (not Ag recognition); CD3 is γε, δε, ζη, and ζζ (90% are ζζ, other 10% are ζη) transmembrane domain is negatively charged, interacts with positive transmembrane domain of TCR chains; ITAMs at bottom of CD3 in cytoplasm impo in signal transduction

Genes coding for TCRs

TCR genes closely related to members of the immunoglobulin gene superfamily. Each chain consists of a Constant (C) and variable (V) region formed by a gene-sorting mechanism similar to antibody formation, i.e. combinatorial joining of VDJ genes and by N region diversification via deoxynuclytidyl-transferase. Recombination is coordinated by RAG-1 and RAG-2. Alpha and gamma regions only have V and J segments. Beta and Delta have V D and J segments. Alpha and beta have ore variable (V) genes than gamma and delta (more diversity with Va and Vb)

hole-in-the-repertoire model

TCR recognizing foreign Ag may be eliminated due to close resemblance to self-Ag (thymic processing)

Discuss the TCR-CD3 complex

TCR-CD3 complex - TCRs join with CDR3 co-receptors to form a complex; CD3 just involved in signal transduction after Ag recognition and expression of αβ and γδ, not involved in Ag recognition

In discussing T cell receptors: What is the TCR-CD3 complex's purpose?

TCRs join with CDR3 co-receptors to form a complex; CD3 involved in signal transduction after Ag recognition, not involved in Ag recognition itself - CD3 also necessary for the expression of both αβ and γδ TCR heterodimers

What is the B cell response to thymus-dependant (TD) Antigen?

TD Antigen · Soluble antigens active in humoral response · Signal 1: cross-linking of mIg by Ag · Signal 2: interaction between CD40 on B cell and CD40L on activated TH cells (direct contact)

Activated macrophages secrete IL-12 induces ______

TH1 response

What does Th1 and Th2 secrete?

TH1: secretes IL-2, TNF and INFy and activates cytotoxic T cells, NK cells and activated macrophages (intracellular infections) TH2: Produces IL-4, IL-10, IL-13 which activates B cells and cause them to produce antibodies (Extracellular infections)

How are cytokines involved in the Th2 subset of T cell development and regulation?

TH2 cells stimulate eosinophil activation and differentiation, help B cells and promote the production of IgM, IgE and non-complement-activating subtypes of IgG. This subset is involved in allergic reactions. -They produce IL-3, IL-4, IL-5, IL-10, and IL-13.

What is the B cell response to Thymus-independent (TI-1) Antigen?

TI-1 Antigen · Components of bacterial cell walls (LPS) · Polyclonal B-cell activators (mitogens) that activate B cells regardless of antigenic specificity · Provides both signals 1 and 2 · No direct physical contact between B and TH cells

What is the B cell response to Thymus-independent (TI-2) Antigen?

TI-2 Antigen · Highly repetitive proteins (flagellin) · Not mitogens · Require cytokines released from TH cells but no direct contact · TI response is weaker than TD

TLRs and their associated PAMPs

TLR-2 : Gram positive bacteria (bacterial peptidoglycan) TLR-4 : Gram negative bacteria (lipopolysaccharide) ENDOSOMAL: TLR-3 : dsRNA TLR-7 : ssRNA TLR-8 : ssRNA TLR-9 : CpG DNA

______ - cells that present Ag to CD8; can be any nucleated cell infected by a virus, intracellular microorganism, cancer cells, or allogenic cells from a graft

Target cells

Discuss the types of cells that present antigens to CD8+ Tc and CD4+ Th cells

Target cells present Ag to CD8; APCs present Ag to CD4

linkage disequilibrium

Tendency for certain alleles at 2 linked loci to occur together more often than expected by chance. Measured in a population, not in a family, and often varies in different populations

how does the C5 convertase generates the membrane attack complex?

The C5 convertase cleaves C5 to C5a + C5b. C5b binds C6, then C7, and C8 come together to form a complex that uses C9 to form a pore (membrane attack complex, MAC), in the microbe membrane. Water flows in through the MAC to cause lysis.

Why is the Haemolytic (Hemolytic) titration CH50 assay a screening test instead of a confirmatory test?

The CH50 test can give a quantitative value for the functional activity of total complement. It does not identify which component(s) are deficient. Hence it is only useful as a functional screening test.

Which ELISA test variant is used to detect antibody (Ab) in a patient's serum and antigen (Ag) in a patient's serum? Both variants use a "tagged" antibody. What is the tag?

The ELISA is a laboratory test to detect antigens or antibodies present in a patient's serum sample. Indirect ELISA is used to detect antibody in patient's serum Sandwich ELISA is used to detect antigen in patient's serum The tag is fluorescent anti-human IgG (Rhodamine or Fluorescein Isothiocyanate FITC tag)

How do the endogenous peptides gain access to the ER lumen and the class I molecules?

The TAP-1 and TAP-2 proteins which exist in the ER membrane are responsible for the transportation of the peptides into the ER. They form a heterodimer linking the cytoplasm of the cell with the lumen of the ER (Transporters Associated with Antigen Processing 1 & 2 are encoded by genes within the MHC)

Expression of a unique TCR (Thymic Cortex Process)

The TCRa chain is transcribed following somatic recombination and allelic exclusion. The preTa chain is down regulated allowing for the cell surface expression of a unique TCR-CD3 complex. (Thymocyte is still a DP at this stage)

What is the antigen on the slide to which the patient's serum is added? (VDRL Test)

The VDRL is a screening test for syphilis. The test is based on the fact that anticardiolipin (antigen) antibodies produced in patients with syphilis cross react with it

Which cytokine enhances the ability of NK cells to kill?

The ability of NK cells to kill is enhanced by activation with the cytokine IL-2.

The role of factor B, factor D, properdin and formation of C3 convertase in the alternative pathway

The active C3b on the microbe surface binds factor B which is then cleaved to Ba and Bb by factor D. Ba diffuses away and Bb binds to C3b forming C3 convertase C3bBb. The C3bBb is stabilized by the addition of properdin (P) forming C3bPBb. This extends its half life. C3bPBb cleaves many C3 molecules. Some of the C3b formed acts as opsonins and the rest attach to C3 Convertase to form C5 Convertase C3bPBb3b. 3) C5 Convertase cleaves C5 to C5a and C5b. C5b binds C6 and C7 which binds to the microbe membrane. C8 and multiple C9 attach forming MAC and microbe is destroyed.

Structure of MHC II

The base is made of Beta-pleated sheets in an immunoglobulin domain. The sides of the groove that hold the peptides are alpha-helices.

Clonal Selection

The binding of B or T lymphocytes to specific antigens results in a large proliferation of antigen-specific activated lymphocytes.

Explain how the complement and intrinsic coagulation pathway systems are linked. Explain how this leads to the production of bradykinin, activation of neutrophils, generation of C5a, and chemotaxis of neutrophis

The complement and the intrinsic coagulation systems are intimately linked via the plasma protein kallikrein, the enzymatic form of the zymogen, pre-kallikrein The conversion of pre-kallikrein to its enzymatic form follows activation of the intrinsic coagulation system in response to tissue damage. This triggers the activation of Factor XII to XIIa. XIIa cleaves pre-kallikren forming kallikren. Kallikren then activates neutrophils (PMNLs) and also cleaves kininogen to bradykinin (vasodilator). It also cleaves C5 to C5a

What is the role of the complement system? Specify the tissue where most of the complement proteins are synthesized

The compliment system is an early defense mechanism against mainly bacteria cells. Compliment proteins are synthesized mainly in the liver however some are also synthesized in macrophages and fibroblasts (compliment proteins circulate as pro-enzymes whose activation requires proteolytic hydrolysis)

Both figures on the slide are the result of renal biopsies; both are the result of a direct fluorescence test. Yet, they appear very different because they are from patients with different diseases. Goodpasture's syndrome versus Systemic lupus erythematosus. Explain the different patterns

The different patterns are the result of Linear Deposition of anti-glomerular basement membrane Ig in Goodpasture's syndrome versus Irregular (lumpy/bumpy) deposition of complexes in Systemic lupus erythematosus

Hematopoiesis

The formation of blood cells derived from pluripotent hematopoietic stem cells in the bone marrow.

Germline hypothesis

The genome contains many loci encoding antibody molecules. B cells express one of these loci. Different B cells express different loci

Describe eosinophils with respect to half-life and percent of circulating leukocytes in a normal, healthy patient.

The half-life of eosinophils in circulation is 8-10 hours and about 1% of circulating leukocytes are eosinophils. Eosinophils are not present in a healthy esophagus but during inflammatory conditions with helminths, or in respiratory airways in atopic or asthmatic patients, eosinophils migrate from bone marrow into circulation and tissues (eosinophilia).

Explain the molecular mechanism that results in isotype switching. Specify the cytokine required to isotype switch to IgE.

The heavy chain constant region is modified leading to isotype switching. DNA encoding the μ and the δ constant regions is excised, resulting in the juxtaposition of the heavy chain variable region to either an α, ε, or γ heavy chain constant region. (This occurs in the germinal centers approximately one week after initial B cell activation by T-dependent antigen.) IL-4 is the cytokine required to isotype switch to IgE.

What is the difference between Type I, II, III hypersensitivity and IV?

The humoral types: I, II, III Mediated by TH1 cells: IV

What is the result of antigen-antibody interaction?

The identification of the paraprotein via immunofixation gel

immunological synapse formation

The immunological synapse forms by the binding of adhesion molecules (integrins) between the APC and T cell. The synapse stabilizes the APC-T cell interaction to facilitate binding of the peptide antigen to the TCR. Note that regions of the MHC molecule physically interact with regions of the TCR.

Explain how the balance of activating and inhibitory receptors on the NK cell determines the fate of the target cell. Name the two molecules that are released from the granules extruded by NK cells.

The inhibitory and activating receptors are linked to different signaling cascades. Whether cells that express Class I MHC are protected or destroyed depends on which signal dominates Perforin and granzymes are released from granules extruded by NK cells. Perforin in the presence of high extracellular Ca concentration forms a cylindrical structure and inserts itself into membrane of target cell and forms a poor for granzymes to pass which then activates proteases of caspase family leading to apoptosis

lymphatic system

The lymphatic system plays an important role in adaptive responses by delivering antigens or microbes to lymph nodes. The lymphatic system begins in peripheral areas of the body as a network of closed lymphatic vessels closely intertwined with blood capillaries and venules.

the major complement proteins

The major complement proteins are C1, C2, C3, C4, C5, C6, C7, C8, and C9, each made by cells in the liver and secreted into the blood stream.

chemotaxis

The movement of cells down a chemical gradient.

What is the physician trying to determine when requesting an indirect immunofluorescence test that consists of a single microscopic slide containing very small slices of frozen tissue of the following tissues: human thyroid tissue, murine kidney, stomach, and liver?

The physician is trying to see if the patient has one of a number of autoimmune disorders by detecting the presence of a soluble autoantibody in the patients serum

Specify the site of a primary immune response. Explain what is meant by a "primary" response.

The primary immune response occurs in the secondary lymphoid tissues and leads to the generation of T cell subsets that secrete distinct patterns of cytokines. Some of the T cells differentiate to memory cells while others undergo apoptosis. Subsequent exposure to the same MHC II induces the reactivation of these memory cells.

Isotype switching

The process by which cells expressing IgM and IgD are modified at the genomic level such that they produce antibodies of different isotypes (IgA, IgE, or IgG) (B cells that have not undergone differentiation to plasma cells secreting IgM will undergo isotype switching and affinity maturation)

Describe somatic recombination (Part 1)

The process by which various gene segments are selected and combined to form a unique variable region in the TCRa and TCRB polypeptide chains during T cell development. This process is initiated by recombinases, products of the RAG-1 and RAG-2 genes Vs, Ds and Js are randomly selected and combined to form the variable region of TCRa and TCRB The rearranged genes are transcribed to mRNA which are translated to an alpha and a beta chain polypeptide = TCR.

Signal 1 and signal 2 as well as the outcome of the combined effects of these two signals on NALP3 Inflammasome

The release of IL-1 and IL-18 is a two signal process: 1) Signal 1: activation of NFκB following PAMP binding to pattern recognition receptors PPR which leads to transcription of pro-IL-1 and pro-IL-18 2) Signal 2: leads to activation of inflammasome by conversion of pro-caspase-1 to caspase-1. Caspase-1 then cleaves the biologically inactive precursors pro-IL-1 and pro-IL-18 to their active forms which are then secreted from the cell (IL-1 is a key mediator of inflammation and IL-18 along with IL-12 stimulates NK cells to secrete IFNy.)

epitope

The specific region of an antigen that binds to an antigen receptor

innate immune protection in the gingival sulcus

The sulcus is formed by hard tissue on one side (enamel) and soft tissue on the other (sulcular epithelium). Sulcular epithelial cells form a protective physical barrier against invasion by microbes. Neutrophils (phagocytic function) are normally present in a healthy sulcus. Neutrophils and epithelial cells secrete defensins and cathelicidins into the gingival crevicular fluid. Macrophages and dendritic cells in the lamina propria (adaptive responses).

6.8 Discuss class switching of Ig heavy chain.

The switch regions are located 2-3 kb upstream of each CH segment except in the delta region contains multiple copies of short repeats (GAGCT and TGGGG) seize of switch regions range from 2-10 kb switch recombinase binds to switch region and mediates recombination cytokine signaling dictates the isotype to which B cell switches after antigenic stimulation of B cells, heavy-chain DNA can undergo additional rearrangement recombined VDJ unit joins with any C gene segment special sequences located upstream of C gene segments called switch regions are involved

To what does titer refer? If a sample is positive at a dilution of 1/160, how do you express the titer?

The titer is the reciprocal of the smallest dilution producing a positive result. If a sample is positive at a dilution of 1/160 you express the titer by finding the reciprocal.

Name the two different types of light-chain constant regions

The two different types of light chain constant regions are kappa or lambda The predominant light chain in Igs are kappa.Kappa chains demonstrate allotypy (presence of allelic forms of the same protein in the population).

Mucosa Associated Lymphoid Tissue (MALT)

The un-encapsulated (more diffuse) lymphoid tissue present in regions underlying the mucosal areas. Some MALT regions are more precisely defined including GALT (gastrointestinal associated lymphoid tissue) and BALT (bronchus associated lymphoid tissue)

Somatic mutation hypothesis

There are a small number of antibody genes which undergo mutation as the B cell matures thus giving rise to B cells expressing antibodies of different specificities

CD4 T cell polarization

There are multiple types of CD4 T helper cells that can arise after naïve CD4 T cells are activated! Differentiation of naïve CD4 T cells into unique subsets is referred to as CD4 T cell polarization.

Specify the number of identical binding sites on a monomeric antibody

There are two identical binding sites on each monomeric antibody molecule

what are the two major classes of T cells

There are two major classes of T cells according to the presence of either of two proteins on their surface, CD4 or CD8. Most T cells in the body are either CD4 T cells or CD8 T cells. T cells that have finished development express one or the other, CD4 or CD8, but never both!

How are cytokines involved in the Th1 subset of T cell development and regulation?

There are two sets of helper T cells that are distinguishable by the cytokines that they secrete. The profile of cytokines is what determines the functions of these two sets of TH cells. - TH1 cells are responsible for cell-mediated functions and for the production of opsonization-promoting and complement-activating 1gG antibodies. These cells are also involved in inflammation rxns, macrophage activation, delayed-type hypersensitivity(DTH) and cytotoxic T cell(TC) activation. - They produce IL-2, IFN-gamma, TNF-Beta, GM-CSF, and IL-3.

All nucleated cells express HLA-class I molecules with a small peptide in the groove. In the absence of infection, the small peptide is a "self-peptide". Deduce why these cells are not destroyed by cytotoxic T cells.

These cells are not destroyed by the T cells because all T cells that recognized self-peptides are destroyed before they mature

Activation of either complement pathway generates proteolytic fragments that play a role in the immune response. Specify their effects

These proteolytic fragments: 1) Opsonin-mediated phagocytosis which eliminates immune complexes (C3b) 2) Enhance vascular permeability by inducing degranulation of mast cells/basophils. (C4a) 3) Induce chemotaxis of neutrophils (C5a) 4) Osmolytic Lysis of bacteria (MAC) (proteolytic fragments also include the C3 and C5 convertases)

why are Neutrophils, monocytes/macrophages, and dendritic cells important?

They are phagocytic cells derived from the myeloid lineage that are vital for destruction of microbes early during an infection.

How are the separated proteins visualized on the gel?

They are stained with a certain dye. (Different stains are used for proteins and nucleic acids.)

Explain why CD80/CD86 interaction with CD28 is critical for T cell activation and clonal expansion

This is critical for T cell activation because this interaction leads to signal transduction events that lead to stabilization of mRNA for IL-2 Both CD80/CD86 ligands are constitutively expressed on dendritic cells. Following clonal expansion Thp differentiates to ThO

Missing Self Hypothesis

This occurs when the cell displaying high levels of specific self MHC self peptide is not killed by NK cell because the interaction of the NK inhibitory receptor with specific Class I-MHC peptide delivers an inhibitory signal (tolerance) (aka when the NK inhibitory interaction is sufficiently strong the cell expressing Class I MHC is protected - cell tolerance is maintained)

Specify the receptor & cytokine that must be expressed for Thp cells to clonally expand

Thp, express IL-2 receptors and secrete cytokine IL-2 that functions in both an autocrine and paracrine manner. Interaction of IL-2 with its receptor induces clonal expansion of antigen stimulated T cells This clonal expansion increases the number of T cells with a specificity uniquely recognizing the peptide/MHC class II complex that induced the initial differentiation

Thymus

Thymocyes are found here, NOT T-CELLS

Thymus (again)

Thymocytes are educated to become T lymphs. T cells learn to recognize self vs. non-self

what is required for antigenic peptides to be presented?

To be presented, antigenic peptides become anchored to the binding groove or cleft of MHC molecules (right). For antigen presentation to occur, an immunological synapse must form at the point of contact between the APC and the T cell!

Explain the role of a "tagged" fluorescent secondary antibody.

To detect the bound auto antibodies (anti-human IgG)

learning objectives

To learn how innate responses provide first-line defense against microbial infections. To understand the importance of barrier functions of epithelial cells (skin, mucosal surfaces). To learn how microbes are sensed and activated by innate cells (pathogen-associated molecular patterns and pattern recognition receptors). To learn antimicrobial effector functions of innate cells (phagocytosis, respiratory burst, antimicrobial molecules).

Learning objective

To learn the elements/events of the acute inflammatory response. To learn the roles of proinflammatory cytokines for regulating acute inflammation. To understand the factors that regulate neutrophil recruitment to the site of infection/inflammation. To learn the role of complement in acute inflammation. To understand the initiation of gingivitis in terms of the acute inflammatory response.

Learning objectives

To learn the two signals needed for T cell activation. To understand how changes in dendritic cell phenotype enhance T cell activation. To understand how coordinated changes in T cell phenotype facilitate T cell activation. To learn the factors that regulate CD4 T cell polarization.

when does the immune response occur?

To preserve health, immune responses must readily occur whenever microbes breach the protective barriers to infection.

What is the role of the immune system in host defense?

To provide defense against antigens and other infectious agents via innate immunity or adaptive immunity.

Explain why a patient's serum or plasma sample is electrophoresed?

To separate the different molecules of the patien't serum based on charge, mass, shape and migratory rates. (Small particles move faster than large particles, which results in a distinct pattern in the gel when molecules are stained with a dye.)

Learning objectives

To understand the differences between innate and adaptive (acquired) responses and to learn the types of leukocytes that carry them out. To understand the differences between primary and secondary adaptive responses. To learn the definitions of an antigen, antigen receptors, and antibodies. To learn the elements of the immune system that combat extracellular pathogens, intracellular pathogens, and viruses. To learn a rudimentary scheme of hematopoiesis, and the differences between primary (bone marrow and thymus) and secondary lymphoid tissues (spleen and lymph nodes).

Learning objectives

To understand the importance of antigen presentation for T cell activation. To learn the two different pathways of antigen presentation (intracellular versus extracellular pathway). To understand the role of major histocompatibility antigens in antigen presentation (MHC restriction). To become familiar with CD4 versus CD8 T cells and learn the requirements for activating each type.

Define the term tolerance and state what happens when we lose this mechanism

Tolerance is the ability of the body to discriminate self from non self molecules (antigens) and destroy non-self molecules. When something goes wrong with this mechanism this leads to autoimmunity a disorder in which self molecules are interpreted as foreign and they trigger an immune response.

What is an application of FACS that we discussed in class?

Tracking of infections such as HIV

Pro-B Cell Stage

Transcription and expression of RAG-1 and RAG-2, CD19, Tdt and CD79a/CD79b which are all required for differentiation of the B cell in the next stage of development. (CD19 is the pan B Cell Marker and it is continuously expressed from this point. Btk is expressed in the transition from Pro-B to Pre-B cell stages)

Discuss the experiment that demonstrates the presence of two antigen processing pathways

Treated target cells with viruses, emetine (inhibit virus), and chloroquine (inhibits endocytic pathway) to see which class of MHC they would be restricted to; virus with no inhibition will be Class I MHC restricted

T/F: the innate and adaptive immune systems regulate each other

True

Name 4 conditions that may result in a false positive test for rheumatoid arthritis.

Tuberculosis Syphilis Systemic lupus erythematosus Viral hepatitis

How many signals are required for T cell activation?

Two!

Blood group Antibodies

Type A: Can receive type A and O blood. Type B: Can receive type B and O blood. Type O: Can ONLY receive type O blood. *Type O* is the *universal RBC donor* because type O lacks anyA or B antigens on the RBC cell surface. *Type AB* is the *universal RBC RECIPIENT* because type AB lacks anti-RBC antibodies in plasma. *Type O* is the *universal PLASMA RECIPIENT* *Type AB* is the *universal PLASMA DONOR*

What are the types of interferons?

Type I -interferon-alpha (leukocytes) -interferon-beta (fibroblasts, epithelial cells, etc.) Type II -interferon-gamma (immune interferon, activated TH1 cells and NK cells)

What are the four types of hypersensitivities in the Gell and Coombs Classification System?

Type I- IgE mediated hypersensitivity (humoral) Type II- IgG or IgM-mediated cytotoxic hypersensitivity (humoral) Type III- Immune Complex-mediated hypersensitivity (humoral) Type IV- Cell-mediated hypersensitivity or delayed hypersensitivity (mediated by TH1 cells and occurs days after re-encountering antigen.)

Myasthenia gravia

Type II HS antigen: AChR; mechanism: Ab inhibits Ach binding; muscle weakness, paralysis

Pernicious anemia

Type II HS antigen: IF of gastric parietal cells Ab neutralizes IF, less B12 absorption

Graves disease

Type II HS antigen: TSH receptor mechanism: Ab stimulates TSH receptors hyperthyroidism

Goodpasture syndrome

Type II HS antigen: basement membrane in kiney glomeruli, lungs mechanism: complement and Fc receptor-mediated inflamm nephritis, lung hemorrhage

Rheumatic fever

Type II HS antigen: streptococcal cell wall antigen Ab cross-reacts w/ myocardial antigen, inflammation, macrophage activation myocarditis results

Excessive amounts of immune complexes in people with high anti-Ag titers can stimulate a strong complement response and neutrophil degranulation causing ___

Type III reaction

Blood Types and their antibodies

Type O: No cell surface ABO antigens, Anti-A and Anti B Isohemagglutinins, universal donor Type A: A antigens, Anti B Isohemagglutinin, receives from type A Type B: B antigens, Anti A Isohemagglutinin, receives from type B Type AB: A and B antigens, no Isohemagglutinin, receives from type A or B (Universal acceptor)

what determines what type of cytokines are produced by APCs?

Type of microbe (PAMPs) or antigen. Type of dendritic cell or APC. The environment the APCs are activated in.

______ - small protein added post-translationally that acts as a tag by which the protein-transport machinery carries a protein to the proteasome for degradation; attached to ε-amino acids on Lys side chain

Ubiquitin

Describe the NLR-Related Protein 3 Inflammasome (NALP3)

Under normal conditions the NALP3 is dormant. It only becomes active when it binds to PAMP or DAMP. On activation the assembly of NALP3 Inflammasome occurs. This is a large intracellular complex comprising of NALP3 and pro-caspase 1 that plays a critical role in innate immunity by mediating the conversion of the zymogen procaspase-1 to caspase-1. Caspase-1 converts pro-IL-1 and pro-IL-18 to the biologically active forms which are secreted from the macrophage.

Paratope

Unique amino acids in the antigen binding region that interact with a specific antigen.

Describe the fate of unselected "Vs", ("Ds") and "Js", the open reading frame and terminal deoxynucleotidyl transferase (Tdt)

Unselected Vs, Ds and Js are deleted. When the recombination of the gene segments do not result in a downstream open reading frame nucleotides are incorporated by a template independent DNA polymerase Tdt and this allows transcription to mRNA to form a unique alpha or beta polypeptide chain

Upon activation, mast cells release what molecules? What do these molecules cause?

Upon activation, mast cells release molecules: - enzymes - toxic mediators: histamine and heparin → increase vascular permeability and cause smooth muscle contraction - cytokines: TNF-alpha → promotes inflammation and stimulates cytokine production; IL-4 and IL-13 → stimulate and amplify TH2 cell response; IL-3, IL-5, GM-CSF→ promote eosinophil production and activation - chemokine: CCL3 lipid mediators → cause smooth muscle contraction, vascular permeability and cause mucus secretion and also activated neutrophils, eosinophils, and platelets

Specify role of IFNγ on MHC class II expression.

Upregulates the expression of MHC Class II & I (Secreted by NK cells (innate immune response) and Th1 cells (adaptive immune response))

Specify the rational for requesting a CH50 complement test. If the results indicate abnormal complement activity, what complement components are targeted for further testing?

Used to assess potential complement pathway deficiencies or complement activation in immune complex associated diseases such as glomerulonephritis, rheumatoid arthritis, or systemic lupus erythematosus. CH50 indicates the presence of C1-C9 in the serum sample. This test will identify those patients with a total, or severe deficiency in any one of the complement proteins, but will not identify those patients with a lower absolute concentration of any given complement proteins. The CH50 test is a measure of total classical complement pathway activity. Tests for C3 & C4 are often used if CH50 test is abnormal.

Direct Recognition

Uses primitive pattern recognition receptors (PPRRs) including mannose receptor and LPS receptor (CD14), scavenger receptors and Toll like receptors (TLRs) that interact with pathogens via pathogen associated molecular patters (PAMPs) on their surface. Each TLR protein recognizes a different type of molecule. When TLR is activated it sends a signal to the nucleus of the macrophage and this leads to the production of cytokines

What are the heavy chains and their segments?

V, D, J, C 1-94 = V gene segment 95-97 = D gene segment 98-113 = J gene segment V, D, and J combine together and encode variable region of heavy chain

Note about VCAM-1, ICAM-1 and ICAM-2

VCAM-1 on vascular endothelium interactions with VLA-4 (CD49d/CD29) on monocytes, lymphocytes and eosinophils. ICAM-1 and ICAM-2 on vascular endothelium interacts with LFA-1 (CD11a/CD18) on neutrophils, monocytes, lymphocytes, and eosinophils. (VLA = Very Late Antigen; slowest of the migrating cells and are activated during inflammation)

6.3 Discuss the gene segments involved in light and heavy chain variable region assembly What is the order of rearrangement?

VH gene rearranges and then VL gene rearranges light chain: 5' L -- exon -- intron -- VJ -- intron -- C3' heavy chains: 5:L' -- exon -- intron -- VDJ -- intron C (gene segments)3'

variable region gene rearrangement

VJ of light: (5'L--exon--intron--VJ--intron--C3') VDJ of heavy: D seg joins to J, then V joins rearranged DJ (5'L--exon--intron--VDJ--intron--C3' DJ before VDJ

Vaccine development

Vaccines are similar to T-cell independent response, but the addition of the polysaccharide epitopes are conjugated to a larger carrier protein which can be ingested and presented on MHC-II thus stimulating a T-Helper Dependent IgG response for production of long term immune memory.

Antibody Structure

Variable domain allows for antigen-binding specificity. the constant domains are for common biological function.

MHC Class III

Various secreted proteins, components of complement system, proteins involved in inflammation

Phagosomes

Vesicles that contain the engulfed pathogen and serve as battlefield where microorganisms are destroyed by phagocytic weapons including lysosomal enzymes, reactive oxygen intermediates and reactive nitrogen intermediates that target the antigen in the phagosome

phagocytes

WBC that engulfs and absorbs bacteria and other small pathogens Macrophages and neutrophils are major and important for innate immunity, communicate to give better adaptive response; eosinophils (parasites) and dendritic cells Macrophages have receptors for Fc complement fragments (C3b)

21.1 (4) Experimental models of immunodeficiency (nude mice, RAG1 & KO mice, SCID mice)

WHAT THE F*CK UTHAY

Why is the ELISA a screening test, but the Western Blot a confirmatory test?

Western Blot is a Confirmatory Test for Human Immunodeficiency Virus (HIV) while ELISA is just a screening test because Western Blot detects specific antibodies to several HIV proteins in a patient's serum. This is in contrast to the ELISA screening test that detects antibodies to one particular HIV protein (generally gp120) in a patient's serum sample. (Confirmation using the Western Blot technique typically requires antibodies to one envelope protein and one core protein)

What does a western blot detect?

Western blotting techniques are used to detect or identify specific proteins in homogenized tissue.

allelic exclusion

What is essential to ensure that each B cell synthesized has only ONE heavy chain and ONE light chain? one heavy gene rearranges---if not productive the other one does---if not productive apoptosis heavy--kappa---lambda

Questions for studying

What is the functional significance of the phenomenon of antigen presentation? Describe each of the two types of antigen presentation pathways. Describe the fate of a protein antigen after it is phagocytosed by a DC. Explain what is needed for an immunological synapse to form between an APC and a CD4 T cell versus a CD8 T cell. Explain why cross-presentation of a viral antigen is unique with respect to activation of CD8 T cells by APCs.

Explain the term "T cell exhaustion"

When T cells lose the ability to synthesize cytokines, proliferate or destroy infected cells due to the binding of PD1. T cell exhaustion is detrimental in the face of chronic viral infections or cancer (FDA approved anti-PD1 antibody which can reverse T cell exhaustion and this is also effective in inducing tumor regression in melanoma patients)

Explain why a T cell can become anergic instead of activated when the TCR is engaged with MHC-peptide complex.

When a T cell interacts with a MHC/peptide complex in the absence of costimulatory interactions the T cell becomes anergic (unresponsive) On the other hand when the T cell interacts with an antigen displayed on an APC in association with peptide/Class II MHC and various costimulatory molecules it is activated

Erythroblastosis fetalis (hemolytic disease of the newborn)

When during a placental bleed or during the birthing process, some of the baby's red blood cells leak into the mother's circulation. When the Rh antigen enters the mother's circulation, it is recognized as foreign and she develops anti-Rh antibodies. When these antibodies are of the IgG isotype, they can cross the placenta and so the fetus is exposed to these antibodies. These antibodies bind to the Rh antigen on the fetal red blood cells, which leads to destruction of the red blood cells = anemia and jaundice

Cross Presentation

When exogenous antigens normally presented only by MHC II molecules are instead presented by MHC I molecules. This can only occur with dendrocytes

When initiated, mast cells have different effects on different tissues: what are these effects and on what tissues?

When initiated they have diff effects on diff tissues: GI tract: increased fluid secretions and peristalsis→ diarrhea and vomiting Respiratory tract: decreased diameter and increased mucus→ congestion Connective tissues/blood vessels: increased blood flow and increased permeability

Cytokine Storm

When oligoclonal activation leads to the secretion of many cytokines

Explain the term leaky B cells

When small numbers of B cells are present in the peripheral blood of most XLA patients. XLA patients have profoundly reduced numbers of B cells in peripheral blood and serum Ig levels of all classes are very low (Suggests the presence of compensatory pathway that can kind of take over the role of Btk)

Primary Lymphoid organs

Where cells originate: bone marrow and Thymus.

Secondary lymphoid organs

Where immune response develops, ie lymph nodes, spleen and tonsils and MALT/GALT/BALT

Example of how AIRE works

Whereas the gene encoding insulin is normally only expressed in pancreatic beta cells in the periphery, the presence of AIRE protein in the medullary TECs allows insulin to be transcribed in the thymus and presented in context of MHC for recognition by thymocytes. Therefore, developing T cells that express TCRs with a specificity for these tissue proteins (presented as a peptide complex with MHC) with high avidity, are deleted before they can be exported from the thymus in a second "round" of negative selection.

PALS of the White Pulp of spleen

White Pulp: contains the lymphoid tissue, arranged around a central arteriole as a periarteriolar lymphoid sheath (PALS). PALS composed of a Germinal Center surrounded by a Mantle and Marginal Zones.

Leukocytes

White blood cells that provide either innate or specific adaptive immunity. Includes: 1. *myeloid cells- non-specific innate* immunity. 2. *non-specific lympohid* cells (*NK-cells*) 3.*Lymphoid* cells: *Humoral (B Cell*) and *Cell mediated* specific immunity (*T Cell*)

21.1 (4) X-linked Agammaglobulinemia

X-linked mutation in Bruton's tyrosine kinase (Btk) defect in B cells extremely low IgG levels and absence of other Ig classes have recurrent bacterial infections

4.3 Differentiate conformational (discontinuous) and sequential (continuous) determinants CONFORMATIONAL

a receptor comes into contact with an antigen with surface amino acids that are discontinuous and come together in a 3D conformation and interact with the receptor's paratope

Blood transfusion reaction: ABO blood group is controlled by...

a single gene with 3 alleles

Adjuvant

a substance that enhances immune response by: 1. increasing the half-life of an immunogen. 2. Increasing local inflammation 3. Improving processing and presentation by MHC.

List two physical barriers to infection

a) Intact skin b) Mucosal linings (Chemical and physical barriers serve as the first line of defense to deter pathogens. Once infectious agents have penetrated these defenses, innate immunity is induced in an attempt to eliminate intruders.)

List three chemical barriers to infection

a) Lysozyme: present in secretions (sweat, tears, saliva etc) splits the cell walls of bacteria. b) Spermine: Located in semen and prevents the growth of bacteria. c) The acid pH of the stomach: Prevents colonization of bacteria

Give three examples of how the site of antigen entry determines the site of initial immune response.

a)If antigen is carried via lymphatics, initial site of adaptive immune response will be the lymph node. b)If antigen is blood-borne, initial site of adaptive immune response will be the spleen. c)If antigen enters via mucosal tissue, initial site of adaptive immune response will be MALT.

Antigenicity

ability to combine specifically w/ products of adaptive response

4.1 Define antigenicity

ability to combine specifically with the products of the humoral and/or cell mediated responses

Immunogenicity

ability to evoke an immune response

4.1 Define immunogenicity

ability to induce a humoral and/or cell-mediated immune response -all cells that have this property also have properties of antigenicity but the opposite is not true

what do dendritic cells (DCs) do after antigen capture?

activated DCs migrate to draining lymph nodes and present antigen to naïve T cells

Complement

additional immune force that participates in killing of microbes in infected tissue sites group of proteins produced by liver that lyses microbes; sequential assembly of complement components to form channels in the membranes of microbial cells, leading to osmotic lysis of microbial cell

21.1 (4) Chronic granulomatous disease (CGD)

affects phagocytes and leads to recurrent or persistent intracellular bacterial and fungal infections and to granuloma formation manifests as pneumonia, infectious dermatitis, and recurrent or severe subcutaneous abscess formation genetically heterogeneous immunodeficiency disorder resulting from inability of phagocytes to kill microbes impairment of killing is caused by defects in the NADPH oxidase enzyme complex that generates the microbicidal respiratory burst phagocytes ingest bacteria normally but cannot kill the bacteria

affinity maturation

after exposure to antigens, those antibodies with higher affinity to the antigen are preferentially selected to survive

What three types of antibodies do hapten-carrier conjugates elicit?

against hapten against carrier against the new epitope formed by combined parts of hapten and carrier

adjuvant

agents that potentiate immune responses (not immunogens) increase the biological half life of vaccine induce production of local inflammatory responses improve antigen delivery and processing by APC

C1 inhibitor deficiency

aka hereditary angioedema; intense swelling episodes, affecting face/GI tract

Leukocyte maturation

all leukocytes derive from self-renewwing HSC in bone marrow; then go to bone marrow or thymus to mature, where they acquire target-binding receptors (pattern recognition receptors, or PRRs, on innate immunity cells, BCR on B cells, and TCR on T cells)

minor variation in am in acid difference in conserved portion of Ig molecules callod allotypic determinants

allotype -minor differences in aa sequence of an Ab within the constant region that results from a mutated allele -no change in isotype or function

T helper cells

allow B cells to mature to plasmas, allows TC to mature and develop cytotoxicity; have TCR and CD4 to recognize exogenous Ag presented on MHC Class II molecules

7.1 anchor residue

allow peptides to bind to MHC, protrude into the pockets in the peptide-binding grooves recognition of antigens by T cells requires that peptides derived from that antigen be displayed in the cleft of an MHC molecule forming a peptide-MHC complex

What is the J chain?

allows for IgM and IgA transport through epithelium consists of dimers or tetramers together

somatic hypermutation

already rearranged VJ and VDJ; occurs in germinal centers of 2' follicles; nuc subs occurs at regions encoding the three CDRs; generates Abs with varying affinities for Ags; Activation-induced cytidine deaminase (AID) helps this and class-switching

4.1 Define epitope

also known as antigenic determinant antigenic site which binds to an antibody OR gives rise to the MHC-binding peptide recognized by the T-cell receptor can be sequential or non-sequential aa complex proteins have multiple overlapping B-cell epitopes some of which are immunodominant usually 6 aa or 5-7 monosaccharides in length

6.9 Discuss the role of alternative RNA splicing in membrane Ig (mIg) and secretory Ig (sIg) forms, and membrane IgM (mIgM) and membrane IgD (mIgD)

alternative splicing is a process during gene expression that results in a single gene coding for multiple proteins B cells ---> mIg plasma cells --> sIg

Types of macrophages

alveolar macrophages-lungs histiocytes-connective tissue kupffer cells-liver mesangial cells-kidney microglial-brain osteoclasts-bone

anchor residues

amino acids at defined positions along peptide that anchor it into the groove of the MHC molecule - anchor amino acids typically interact with the ends of the closed groove of the MHC class I molecule

What is agglutinin?

an antibody, lectin, or other substance that causes agglutination

Give examples of innate immunity.

anatomical barriers and secretions phagocytes and phagocytosis moleculear sensors- pattern recognition receptors inflammaion fever other factors include cytokines, complement, clotting factors, acute phase proteins

Peripheral B cell tolerance

anergy if no T cell help; suppressed by Tregs; Upreg of Fas that binds FasL on T cells

MHC-ass'd autoimmune disease

ankylosing spondylitis, RA, DM type I, pemphigus vulgaris mechanism? possibly the way the MHC proteins encoded by faltering alleles present culprit self-peptide to T cells

Repeat exposure to same microbe

anti-microbe memory B cells (present in higher numbers than naive B cells) quickly activated and give greatly expanded secondary Ab response high affinity non-IgM Abs (mainly IgG0

What is an example of cross-reactivity?

antibody against Group A Strep also reacts with human myocardium and may lead to rheumatic fever antibody elicited against Epstein-Barr virus reacts with SRBC and by measuring the heterophile against SRBC clinically, indirect evidence of recent EBV infection can be determined

4.1 Define paratope

antibody-combining site on antibody located in the variable region of an antibody that is composed of 3 CDRs

What is the progression of antigen and lymphocytes through the spleen?

antigen and lymphocytes --> marginal zone --> dendritic cells process antigen --> activation of B cells and Th cells in PALS --> activated B cells with some Th cells migrate to the primary follicle forming a characteristic secondary follicle which then forms the germinal center

Sensitization occurs when..

antigen is processed by APC and presented via MHC Class II to TH cells that become activated by TH1 cells

how are T cells activated?

antigen presentation

3.15 (2) Discuss the types of dendritic cells.

antigen-presenting cells that are classified according to their location Langerhans cells (in skin) Interstitial dendritic cells (in connective tissue of most organs) Interdigitating dendritic cells (in lymphoid tissues) Circulating dendritic cells (in bloodstream) Follicular dendritic cells (in lymph nodes)

Epitope

antigenic determinant that is recognized by Ag-binding site of Ab (paratope); hydrophilic aa on surface of immunogenic molecule; can be sequential or non-sequential aa

idiotype

antigenic determinants of variable region

What are histocompatibility antigens?

antigens that are responsible for rejection of foreign tissues

Kinin

any of a group of substances formed in body tissue in response to injury. They are polypeptides and cause vasodilation and smooth muscle contraction. *Bradykinin* is very important in both *inflammatory reactions* and *pain signalling* *INC Vasodilation, INC vascular permeability, INC Pain sensation*

Outcomes of central tolerance:

apoptosis (T and B cells); development of regulatory T cells (Tregs), or receptor editing (B cells)

Thymic selection

apoptosis of cells that: -unable to recognize self-MHC -have high affinity for self-Ag on MHC

cytokines (what are the, what makes them, and what do the do?)

are proteins produced by many cell types including all leukocytes, and regulate proliferation, activation, differentiation, and communication To be effective, cytokines must bind to specific cytokine receptors expressed on the surface of cells.

CD4+ T helper/CD8+ cytotoxic T cells

are responsible for cell-mediated immunity needed to combat intracellular pathogens (eurlikia and other intracellulars that arent killed by macrophages); T helper are also vital for REGULATION OF HUMORAL RESPONSES and take care of any infected cell

Function of AIRE in central tolerance

autoimmune regulator (AIRE) is a TF that directs the expression of antigens only found in some peripheral tissues on the epithelial cells of the thymus; this allows - selection of thymocytes that recognize tissue-specific self antigens

What are lymph nodes and describe their structure.

bean shaped structure at juncture of lymphatic vessels that filters antigens from lymph -packed with macrophages, dendritic cells, and lymphocytes -first organized lymphatic tissue to encounter antigens cortex = outermost layer paracortex = layer just beneath the cortex medulla = innermost layer (secondary lymphoid organ)

TCR rearrangement

beta chains exhibit allelic exclusion, alpha chains do not; limited diversity compared to Igs; NO somatic hypermutation

Antigen

bind to components of immune response but doesn't illicit response (eg. hapten)

4.1 Define immnunogen

bind to components of the immune response and evoke an immune response ex: immunogen eliciting allergic response to allergens "All immunogens are antigens, but not all antigens are immunogens."

4.1 Define antigen

bind to components of the immune response but do not elicit an immune response ex: haptens

Anti-PD-1 antibody

binds PD-1 on T cell; prevents CD8+ cell apoptosis

Penicillin as a hapten

binds proteins to create neoepitopes, which can be processed to lead to Th2 response

IgE

binds to Fc receptors on mast cells and basophils, induces degranulation, responsible for allergy symptoms

Barrier epithelial cells

block microbes from penetrating mucosal surfaces and also play an active role in innate defense.

lymphatic system

blood circulates under pressure in the capillaries; plasma can escape and leak into the tissues, much of this interstitial fluid goes back to the blood and the remaining (lymph) is captured in the lymphatic capillaries

What are manifestations of Type II?

blood transfusion reactions, erythroblastosis fetalis, and autoimmune hemolytic anemia (AIHA)

If ____ or ____ rearrange nonproductively, the B cell will not mature

both heavy chain alleles or all four light chain alleles (losing kappa first)

Presentation of antigen samples to T cells

by dendritic cells, macrophages, and B cells, all of which internalized the antigen in peripheral lymphoid organs

systemic anaphylaxis:

by drugs, serum, venoms, peanuts - Enter intravenously and cause vascular permeability, smooth muscle contraction, tracheal occlusion, circulatory collapse, and death. This due to mast cell degranulation and general release of histamine. - Food allergy: allergen cross-linking of IgE on mast cells in upper GI tract from ingestion of allergen. Then it diffuses into the blood vessels. (Some can cause TH2 responses and IgE production but IDk why) *Basophils also play important role in food allergies

how are antigens taken in by phagocytosis normally processed?

by the extracellular pathway!

how are granulocytes identified by staining patterns?

can be distinguished by the staining patterns of their cytoplasmic granules as well as by their irregularly shaped nuclei (A, neutrophil; B, eosinophil; C, basophil).

What do dendritic cells do?

capture antigen in tissues and then go to the lymphoid organs to present the antigen to T lymphocytes -more potent APC than macrophages or B cells

Cell-mediated immunity

carried out by T cells; required for destruction of microbes that can survive within host cells.

humoral immunity

carried out by antibodies produced by B cells; required for destruction of microbes in extracellular environments especially mucosal surfaces.

List some microbial peptides produced by skin.

cathelicidin (IL-37) beta defensin (hBD-1,2,3) psoriasic (kills E.Coli/antibacterial activity)

C3 defects

cause severe immunodeficiency; absence of C3 abrogates all fxns of complement, predisposing to infections

primary immunodeficiency

caused by mutations affecting immune responses -most present in clinic as recurrent or overwhelming infections in very young children - milder inherited abnormalities may not show clinical signs until later in life -may affect adaptive or innate immune systems and most defects affect either the myeloid or the lymphoid lineages of cells -mostly inherited

21.1 (4) Leukocyte adhesion deficiency (LAD)

cell adhesion molecules (CAMs) are affected defect in common CD18 of the receptors - LFA-1, Mac-1, gp150/95 neutrophils do not express CAMs and therefore are unable to adhere to the endothelium during an inflammatory event susceptibility to both Gram + and Gram - bacteria occurs

non-professional APC

certain cells (fibroblasts, glial cells) can express Class II and co-stimulatory molecules and function as APC for short period of time

Isotype switching

change in the heavy chain isotype expressed by a given B cell thereby allowing other heavy chain isotypes to be expressed after antigen exposure. Ex: switching from IgM to IgG3. Stimulated by antigen exposure + cytokines produced by TH cells and interaction with TCell surface molecules.. V region and antigen binding specificity DO NOT change.

Chemical mediators of inflammation

chemical mediators can act on the local level or systemic level. Some local mediators can move into the blood stream and have systemic effects as they work at longer distances.

Interleukin-8 (IL-8)

chemoattractant that triggers adhesion and subsequent diapedesis of neutrophils into target tissues.

what results from activation of naive T cells?

clonal proliferation and differentiation into effector and memory T cells.

combinatorial vs. junctional diversity

combinatorial: due to VDJ arrangements; mediated by RAG enzymes junctional: add'n/deletion of NTs @ jxns of recombining VDJ segments; contributes to high degree of variability in CDR3 regions. Add'n of P NTs (DNA pol) and N NTs (terminal deoxynucleotidyl transferase TdT); exonucleases also remove nts from VDJ @ sites of recombination

series of 30 serum proteins which together compromise 5% of the total serum proteins - although part of innate defense, works with the adaptive system and circulates as zymogens

complement

Membrane attack complex (MACs)

complement components C5b-C9 requires sequential, pre-assembly of C3convertase and C5convertase

MHC Class III

complement proteins, TNF and lymphotoxin.

7.1 MHC

complex of genes encoding cell surface molecules involved in self/non-self recognition, transplantation, antigen presentation to T cells, immune regulation, and immune responsiveness -discovered as the genetic locus whose products were responsible for rapid tissue rejection of tissue grafts exchanged between inbred strains of mice (Peter Gorer and George Snell)

MHC

complex of genes encoding cell surface molecules involved self/nonself recognition and Ag presentation to T cells, and transplantation; loci are highly polymorphic having many forms of alleles, co-dominantly expressed in each individual from both parents; proteins synthesized in rough ER

Complement system

component of the innate immunity that either alone or with the help of antibodies, recognize and attack foreign molecules resulting in complement cascade formation resulting in hypotonic lysis, increased efficiency of phagocytosis, and directed leukocytte migration to augment clearance of foreign molecules/pathogens (immune response) Classical activation= antibody mediated Alternate activation= no antibodies required

S1P

concentrations are greater in blood and lymph than in lymph nodes; high levels keeps expression of S1P receptor on T cells low when cell enters node (lower S1P levels), it upregulated receptor expression; if it doesn't find its peptide:MHC it follows gradient out If it does find its peptide and gets activated, S1P receptor levels are depressed for several days; keeps it in T cell zone where it proliferates/differentiates; when done, S1PR incr., lose expression of CCR7 and L-selectin

7.1 polymorphism

condition of occurring in several different forms, presence of genetic variation within a population, upon which natural selection can operate -MHC loci are highly polymorphic and many alternative forms of alleles at each loci

If immune complexes aren't cleared effectively, they may deposit in tissues, triggering release of inflammatory mediators and vasoactive mediators. -Proteases released may damage ____ -____ may form as complexes activate platelets

connective tissues Clots

Mast cells are present in:

connective tissues mucosa of GI respiratory tract

Recombination signal sequences (RSS)

conserved palindromic heptamer and AT-rich nonamer; either 1-turn or 2-turn; similar RSS cannot join so V segs don't join other V segs kappa=1-turn V and 2-turn J lambda=2-turn V and 1-turn J heavy=2-turn V&J, 2 1-turn D (one at each side)

What is secretory component?

consists of give Ig-like domains that bind the Fc regions of an IgA dimer and protects the hinge region from protease digestion

Describe the paracortex of lymph nodes.

contains T lymphocyte and interdigitating dendritic cells that express high levels of class II MHC molecules paracortex is also called thymus-independent area

What are the compartments of the thymus and what do they do?

cortex = outer region -densely packed with immature lymphocytes called thymocytes medulla = inner compartment -sparsely populated with thymocytes

Describe the cortex of lymph nodes.

cortex contains mostly B cells, follicular dendritic cells, and macrophages arranged in clusters called primary follicles also called thymus-independent area following antigenic stimulation, the primary follicles enlarge and become secondary follicles the germinal center (GC) contains proliferating B cells and plasma cells interspersed with macrophages and dendritic cells from blood, lymphocyes arrive at the lymph node through specialized endothelial cells called high endothelial venules (HEV) cells move into lymph node by extravasation process

Therapy strategies for T cell-mediate disease

corticosteroids, anti-inflamm TNF inhibitors (Abs, mimetics) B7 inhibitors, anti-cytokines or their receptors

Therapy strategies for antibody-mediated HS (II and III)

corticosteroids, anti-inflammatory drugs plasmapheresis to reduce levels of circulating pathogenic Abs or immune complexes IVIG pooled from healthy donors (block FcR on myeloid cells?) Rituximab (anti-CD20 to deplete B Cells)

What are some specific ways mucus is expelled from the body?

coughing, sneezing expels mucus

Immunosuppression of TCR signalling

cyclosporine inhibits calcineurin (prevents NFAT from PLCgamma) Rapamycin blocks response to IL-2 and prevents Akt and mTOR activation in PI-3-kinase pathway CTLA4 binds B7 on APCs, prevents interaction w/ CD28 on T cells block of inhibitory PD-1 receptor on T cells, so T cells can proliferate and kill cancer cells

allergen in the feces of dust mites is ______ which is also homologous to the protease papain (From a papaya fruit)

cysteine protease Der p1 **Occupational allergies occur - example: some individuals in the meat industry develop an occupational allergy to meat tenderizer - cause of allergy is the papain of papaya origin in the tenderizer

Erythropoietin

cytokine that regulates differentiation of RBCs

substances that modulate the immune response which are made by specific cells (innate)

cytokines

DAMPS (what is it, what do they do, and what are some examples of specific ones?)

damage-associated molecular patterns are produced by stressed, damaged, or dying cells; also called danger molecules or alarmins. Some are patterns, but not all DAMPs include heat shock proteins, adenosine triphosphate (ATP), potassium ions (K+), and nucleic acids. DAMPs stimulate non-infectious inflammation by activating macrophages. ex. Most cells loaded with K+ (more inside then outside) when damaged leak K, ATP (can stimulate damage responses), damps can result from innate imune response to microbe. Is why you can still have symptoms/feel sick after

21.1 (4) Wiskott-Aldrich Syndrome (WAS)

defect in CD43 (sialophorin), a cytoskeletal glycoprotein cellular and humoral immunodeficiency normal level of T and B cells low level of IgM persistent thrombocytopenia (low platelet count) increased risk of autoimmune disease and hematological malignancy is an X-linked recessive genetic condition that affects only boys 1 case per million live male births in US morbidity and mortality has improved with abx, advances in blood banking, and stem cell transplanation

21.1 (4) Severe combined immunodeficiency (SCID)

defect in lymphoid development that affects T cells either alone or in combination with B cell and/or NK cell involvement represents a group of rare, sometimes fatal, congenital d/os characterized by little or no immune response affects 1/50,000 birthds, 100,000 children born in the USA with disease commonly known as "bubble boy disease" patients are susceptible to recurrent infections like pneumonia, meningitis, and chicken pox and can die before end of first year of life through invasive new treatments such as bone marrow and stem cell transplantations, we can save SCIF patients

Hyper IgM syndrome

defective expression of CD40L on Th cells, prevents help to B cells for Ig class switching predisposes to pyogenic infections (from pus-inducing extracellular microbes)

What can lead to immunodeficiency of both the humoral and cell-mediated branches of the immune system?

defective intercellular communication (mutations of genes that encode receptors or signal transduction molecules) defects in genes controlling Ig or T cell receptor rearrangement (absence of RAG1 or RAG2)

What is the difference between dendritic cells and follicular dendritic cells?

dendritic cells are antigen-presenting cells of the immune system that are derived from the bone-marrow HSC follicular dendritic cells are cells of the immune system found in primary and secondary lymph follicles of the B cell areas of the lymphoid tissue, derived from the mesenchyme

langerhans cells

dendritic cells in the skin

Adaptive immunity

develops after antigen encounter; adapts to unique characteristics of each antigen (takes several days); has memory, so the adaptive system to subsequent encounters w/ same antigen is faster and of much greater magnitude than the response on first encounter

Light chains and heavy chains are encoded by separate multi-genes located on ________ chromosomes

different

determinant selection model

different Class II MHC molecules differ in their ability to bind to processed Ag

Direct vs. indirect allorecognition

direct: T cell recognizes unprocessed allogeneic MHC molecule on graft APCs indirect: T cell recognizes processed peptide of allogeneic MHC molecule bound to self MHC molecule on host APC

Paroxysmal nocturnal hemoglobinuria (PNH)

due to defects in DAF; Hgb released from lyses RBCs released in blood, esp. concentrated in morning

secondary immunodeficiency

due to loss of immune function as a consequence of other disease or exposure to various environmental agents ex: retrovirus HIV-1 is the causative agent of AIDs

Why is it difficult to treat HIV?

due to the poor proofreading quality of viral RT, there are constant mutations in the strains of HIV, making it difficult to make an antibody that will be able to keep up with the changes to inhibit the viral strains

when are dendritic cells activated?

during infection by pamps

Receptor editing of B cells (central B cells)

edits IgL

Leukocyte Adhesion deficiency

elevated WBC, inability of PMNs, macrophages, T cells to traffic to sites of infection LAD-1: mutation in CD18, a beta chain integrin LAD-2: mutation in E- and P selectins

RAG-1 and RAG-2

encode V(D)J recombinase that recognize RSS, bring segments into proximity

Phagocytosis

engulfment of large particles (e.g., microbes) results in microbial death and processes antigens for activation of adaptive responses Phagocytosis is a gradual process; as PAMPs bind to PRRs, the phagocyte membrane gradually "zippers" around the microbe until it is completely engulfed.

In Immunofluorescence, the primary antibody recognizes the target molecule (antigen) and binds to a specific region called the ______.

epitope

What characterizes generalized type III?

excess of immune complexes circulating. - these complexes are less apt to be destroyed by phagocytes. More easily pass thru basement mem of blood vessel walls. - antiserum therapy can lead to form of Abs to foreign serum proteins that then form immune complexes in circulation= serum sickness

T cell activation depends on the balance of what two things?

excitatory and inhibitory signals

what causes DC maturation

exposure to microbes (pamps

Cytotoxicity

extracellular killing; achieved by lysis of microbial particles or by inejction of toxic substances into microbes or infected host cells

Mature B cell development occurs in the ___ in fetuses and in ___ in adults

fetal stage - yolk sac, fetal liver and fetal bone marrow adult stage - bone marrow

Pattern recognition receptors (PRRs)

few dozen, each of which binds to common component present on a category or subcategory of microbes or on damaged tissue (ie flaggellin) INTRACELLULAR or CELL SURFACE

What are the V regions? C?

first 100-110 aa of the amino terminal region of the L and H chains where the interaction with the antigen takes place, Igs with different specificities vary greatly in their V region the rest of the Ig molecule does not vary much when comparisons between other Igs are made so the rest is the constant region

IgM

first Ig to be synthesized; monomeric M is membrane-bound in B cells (naive, 1st to see pathogen, primary response); pentameric M is secreted form; J chain stabilizes pentamer & allows for transport to epithelial surfaces

2.12 Discuss innate imumunity and adaptive immunity. INNATE

first line of defense that acts to prevent agents from invading, colonizing, and spreading within a host -buys time for adaptive response to become active -cells and many components present in higher amounts prior to encounter with pathogen -not specific for any pathogen

structures composed by aggregates of lymphoid and non-lymphoid cells surrounded by a network of lymphatic capillaries

follicles

Tfh cells

follicular helper T cells assist B cells w/ antibody production in the follicle of PLOs (don't exit the PLOs like other effector cells)

4.2 Discuss the properties of antigens

foreign-ness (recognizes the albumin as foreign to elicit immune response) high molecular weight >5,000 da (high molecular weights are immunogenic) chemical composition and complexity (homopolymeric compounds are not immunogenic because there is no chemical complexibility-- need to have primary, secondary, tertiary, and quaternary struture) degradability (antigens must be processed by APC into small fragments and noncovalently bound to MHC expressed on the surface of APC) genetic composition (controlled by genes mapped within the M HC) dose, route of administration (subcutaneous, intravenous, gastrointestinal)

What are characteristics of immunogen?

epithelial cells

form protective barriers to infection (skin, mucosal surfaces) and secrete antimicrobial molecules.

Hematopoiesis

formation of blood cells from hematopoietic stem cells (HSCs) that are multipotent or pluripotent; happens in liver during development then bone marrow in adults

coding joint

formed from combining of coding regions and product of V(D)J recombination

TCRs

found on cell surface

BCRs

found on cell surface and as soluble molecules (Abs, or Igs)

Avidity

functional affinity- strength of the interaction of antigen molecules having multiple epitopes with antibodies having more than one paratope multiple epitope-paratope interactions are involved nAb + mAg = AbnAgm cumulative binding strength (or affinities) of all antibody-epitope pairs

hinge region

gamma, delta, and alpha heavy chains have a small region between CH1 and CH2 domains that is rich in proline and cysteine, presence of proline gives flexibility at the polypeptide region

7.1 co-dominance

genetic scenario in which neither allele is dominant or recessive and both get expressed ex: type AB blood, where both A allele and B allele equally expressed Ex: roan fur in cattle - white hair and red hair are equally expressed Ex: MHC genes are co-dominantly expressed in each individual, alleles from both parents are expressed

Progenitor

give rise to specific cells; lymphoid (B, T, NK) and myeloid (RBCs, leukocytes)

myeloid lineage products

gives rise to blood monocytes, dendritic cells, and granulocytes (neutrophils, basophils, eosinophils).

erythroid lineage produces

gives rise to erythrocytes (red blood cells) and platelets.

lymphoid lineage products

gives rise to lymphocytes (B and T cells) and natural killer or NK cells.

MHC Class II

glycoproteins expressed on the cell surface of APCs; two polypeptides as dimer (α and β chains); present antigens to TH cells; α1 and β1 form open cleft; Ags are exogenous

What types of cells make mucus?

goblet cells

HIV life cycle

gp120 binds CXCR4/CCR5; HIV RNA genome enters cell and RT-mediated synthesis of proviral DNA DNA integrated into genome cytokine activation of cell, TX of genome; synthesis of HIV proteins, assembly of virion core expression of gp120 on cell surface and budding of mature virion

xenograft

graft b/n different species

allograft

graft b/n individuals of different strains

xenograft

graft between different species ex: skin graft from a pig to a human

isograft

graft between identical individuals ex: skin graft from one mouse strain to another mouse of the same strain ex: skin graft from one identical twin to the other

allograft

graft between individuals of different strains ex: kidney transplant from one human to another where the donor and recipients are NOT identical twins ex: skin graft from one strain to another mouse strain

autograft/isograft

graft from individual to itself/identical individual

autograft

graft from one individual to itself ex: skin graft from one part of the body to another

Neutrophils

granulocyte that is first cell to arrive at inflammation site; phagocytosis; oxygen dep and indep killing mechanisms; primary and secondary granule lysosomes

Describe the secondary humoral response.

greater magnitude response short lage phase (1-2 days) - memory cell response long duration - months short peak response (2-7 days)

B cell maturation

happens in bone marrow; pro-B --> pre-B (IgH)--> immature B --> mature B signalling through pre-BCR is req'd for expression of IgL (kappa then lambda), cell proliferation, and developmental progression to mature B; lack of signalling = apoptosis

T cell maturation

happens in the thymus; double-negative --> pre-T cell (pre-TCR, only TCRbeta) --> double-positive --> CD4/8 signalling through pre-TCR req'd for expression of TCRalpha, proliferation, and developmental progression to double positive stage

T cytotoxic cells

have TCR and CD8 to recognize endogenous Ag presented on MHC Class I molecules (which are on all nucleated cells)

Mast cells

have granules containing histamine; develop allergies; leave bone marrow undifferentiated & enter tissues to become mast cells

Fungi

have nuclei, therefore are eukaryotes; cell wall composed of polysaccharides and polypeptides can be single cell yeasts or multi-cell molds (which form long filaments)

TCR

heterodimers composed of two chains (alpha-beta or gamma-delta); structure similar to Ig; V and C regions; gamma-delta ones are CD4/8 neg and recognize phospholipids; alpha is like light, beta like heavy (gamma and delta, respectively) rearrange

2.12 Discuss innate imumunity and adaptive immunity. ADAPTIVE

highly pathogen-specific -second line of defense that works with innate defense -mediated by antigen presenting cells and lymphocytes -relies on gene rearrangement and clonal expansion for detection of specific antigens of the invading pathogen

7.1 HLA

human leukocyte antigen, gene complex encoding the MHC proteins in humans -study of individuals who had received multiple blood transfusions or individuals who had received kidney transplants and later rejected the transplanted kidney contain alloantibodies that react against antigens present on the leukocytes (alloantigens) of the donor and these studies were used to construct the locus

What are the two types of adaptive immune responses?

humoral immune response cellular immune response

antigenic detrminants of the variable region, the unique aa sequence in the variable region of each Ab clone can stimulate an immune response in the same species

idiotype

What is the sequence of events in the thymus?

immature lymphoid cell --> enters cortex --> divides --> migrates to medulla --> becomes mature T cell --> leaves thymus and enters circulation

Type III Hypersensitivity: Immune Complex-Mediated Pathogenesis

immune complex (drug-antibody) adsorbs loosely to the RBCs Complement is activated, and the RBCs are considered "innocent bystanders", resulting in hemolysis

Type III mechanism:

immune complex mediated - Ag-Ab complexes form and deposit in various tissue locations ---> Stimulation of strong complement response: Inflammation mediated by massive infiltration of neutrophils. Ex.) Immune complex (drug-antibody) adsorbs loosely to the RBCs --> Complement is activated, and the RBCs are considered "innocent bystanders", resulting in hemolysis *Excesssive amounts of antigen leads to circulating Ag-Ab complexes

carrier molecule

immunogenic molecule that is recognized by T cells in an antibody response ex: bovine serum albumin (69,000 Da) keyhole limpet hemocyanin (>2,000,000 Da)

Chronic granulomatous disease (CGD)

inability of macrophages and PMNs to kill phagocytosed microbes due to mutation in phagocyte oxidase

Toxoid vaccines

inactivation of toxin by formaldehyde or heat to toxoid form; Abs form against toxoid, and still are active against toxin if ever introduced diphtheria, tetanus, botulism

signs of gingivitis

include neutrophil recruitment into the sulcus, and redness, swelling, and painful irritation of the gingival tissues.

Fever

increased body temp; accelerates metabolism and improves circulation, destroys old cells, increased lympocytes

What is the outcome, in immune response terms, if a species has limited MHC polymorphism?

increased susceptibility for diseases

B cell activation by T-independent antigens

independent antigens are typical capsular polysaccharides and lipids w/ repeating identical units/no protein component engage Ab molecules on surface of B cell and stim CR2 or TLR to stimulate B cell to express survival and cycling proteins, and CCR7; no peptides, so no presentation via MHCII multple interactions of BCR molecules w/ repeating epitopes is sufficient to activate, proliferate, and terminally differentiate B cell to short-lived IgM-secreting plasma cells

HLA and disease

individuals with HLA allele for certain disease compared to same allele in general population indicates relative risk of DZ -risk=1 then no association of DZ w/HLA allele -risk>1 then possible association exists

What do defects in myeloid lineage affect?

innate immunity, especially phagocytic activity

Describe the medulla of lymph nodes.

innermost layer of lymph node sparsely populated with lymphocytes plasma cell that secrete antibody are present

neutropenia

insufficient numbers of neutrophils (neutropenia) result in an increased risk of acute bacterial infections.

4.3 Differentiate conformational (discontinuous) and sequential (continuous) determinants SEQUENTIAL

interact with the paratope based on their primary structure

HLA gene complex

interchanged with MHC, same thing. In humans, the MHC loci is designated as HLA. HLA Class I consists of: HLA- A, B, and C loci. HLA Class II region consists of: HLA- DP, DQ, DR.

glycoproteins made in response to viral infections (innate)

interferons

How is HIV spread?

intimate contact of infected body fluids -vaginal/anal intercourse -receipt of infected blood/blood products -passage of HIV from mother to infant -dendritic cells in virus-exposed areas may take up and harbor virus and pass it on to CD4+ T cells

Phagocytosis

intracellular killing, achieve by ingestion and degradation of microbial particles; carried out by neutrophils, macrophages, and monocytes

Bruton's tyrosine kinase

involved in signal transduction through the pre-BCR; defect results in B cell immunodeficiency, X-linked agammaglobulinemia (XLA)

constant region determinants, defines each heavy chain class and sub-class and each light chain type and sub-type

isotype

What are common antimicrobial components contained in mucus?

isozyme IgA lactoferrin lactoperoxidase beta-defensins cathelicidins *antimicrobial peptides, also called host defense peptides (HDPs), are part of the innate immune response found among all classes of life.

MHC (HLA) Class II deficiency: Bare lymphocyte syndrome

lack of CD4 T cells; decreased cell-mediated and humoral immunity (no T cell help for macrophages, B cells) lack of MHC class II expression on APCs, and thymic epithelial cells due to mutation of genes encoding TFs for MHC II expression-->thymocytes w/ class II restricted TCRs cannot undergo + selection

How tumors evade immune response:

lack of T cell recognition of tumor (failure to produce tumor antigen); mutations in MHC genes or genes needed for antigen processing; inhibition of T cell activation (production of immunosppressive proteins or expression of inhibitor cell surface proteins)

What are the light chains and their segments?

lambda and kappa chain family V, J, C 1-97 = V gene 98=101 = J gene segment V and J combine together and encode variable region of light chain

What is the spleen and how does it function?

large organ situated in the upper left abdominal cavity traps blood-borne antigens antigens/lymphocytes reach the spleen through splenic artery primary lymphoid follicles are attached to PALS, are rich in B cells, some of them are within the germinal center marginal zone is peripheral to PALS and contains macrophages and lymphocytes (secondary lymphoid organ)

What is encoded at the 5' end of each V gene?

leader peptide

neutrophils

leave the blood stream to storm the site of acute bacterial infections

monocytes

leave the bloodstream and mature into macrophages in all tissues of the body; macrophages are vital for regulation of the acute inflammatory response and for stimulating adaptive immune responses through the process of antigen presentation.

Eosinophils

less phagocytic than neutrophils; important in immunity against parasites

Memory B cells

live for years; circulate through PLOs to occasionally receive low-level "bystander" cytokine stim.; others home to mucosal tissues

Arthrus reaction

local type III hs: subcutaneous challenge with Ag; localized raction with IgG in skin; MINUTES central wheal of edema (plasma leakage), flare of vascular congestion (vasodilation)

Activation of the complement system produces anaphylatoxins (C3a, C4a, C5a) =

localized mast cells degranulate and increase vascular permeability

If immune complexes stay and accumulate at the site of antigen entry, ____

localized rxn occurs called Arthus rxn.

What results from the lack of thymus?

loss of T-lymphocyte development Digeorge's syndrome: congenital birth defect in humans loss of antibody formation that requires helper T cells, cell-mediated immune responses increase in infection (because thymus is the site of antigenic diversity)

Describe the primary humoral response.

low magnitude response long lag phase (5-7 days) to allow for activated B cells to secrete antibody short duration long peak response (10-17 days)

3.10 Define Natural Killer cells

lymphocytes that can kill host cells (i.e. virus-infected cells) without making their own unique antigen-specific receptor (do not require Ab or TCR- innate immunity only) -releases lytic granules that kill some virus-infected cells

In DTH, ___ are the effector cells

macrophages

What are three examples of APC?

macrophages dendritic cells B cells

Humoral immunity

main form of protection against extracellular microbes and microbial toxins; and against intracellular microbes before they invade host cells

Generation of B cell memory

majority of activated proliferating follicular B cells --> plasma cells some: T-cell contact and cytokine help lead to differentiation to long-lived memory B cells--don't secrete Ab but BCR is class-switched and high affinity. They are activated faster than naive B cells on repeat encounters and generate plasma cells and memory B cells

21.1 (4) Complement deficiencies (properdin and MBP defect)

many complement deficiencies associated with increased susceptibility to bacterial or fungal infections and/or immune complex disease due to -defect in properdin -defect in mannose binding lectin protein (MBP)

Graft vs. host disease

mature T cells from donor (after HSC transplant) attack the host; share features w/ T cell mediated autoimmune diseases

Humoral immune response

mediated by B lymphocytes that proliferate and differentiate into plasma (secrete Abs or Igs) and memory cells

Cellular immune response

mediated by T lymphocytes that have TCRs that bind to Ag epitopes presented by APC on MHC APCs=macrophages, dendritic cells, B cells

B cell receptor

membrane Ig w/ disulfide linked a/b heterodimer

Fc receptor

membrane glycoproteins expressed by many cells; leads to effector functions like opsonization (receptor specific to isotype)

anaphylaxis

mild (urticaria/hives) to life-threatening (shock) systemic Ag distribution, systemic mast cell degranulation, systemic complement activation (C5a, C3a, C4a), rapid fall in BP due to vasodilation, airway obstruction due to laryngeal edema

gingivitis

mild inflammation of the gum tissue that can progress to severe periodontal disease (destruction of alveolar bond and tooth loss).

Localized tissue and vascular damage notable ~4-8 hours w/ edema and erythema varying in severity from ____ to ____

mild tissue damage to tissue necrosis

Mononuclear cells

monocytes and macrophages are types of... -macrophages are larger and have more phagosomes & hemolytic enzymes -granulocyte-monocyte progenitor cells---promonocytes---mature monocytes---circulate in bloodstream for 8 hours---migrate to tissues---terminally differentiated macrophages (activated by Ag & enhanced by cytokines, IFN-gamma)

IgG

most abundant class: IgG1,3,4 cross placenta and protect fetus IgG3 potent complement activator, then 1,2 (not 4) IgG1,3 effective at opsonization bc high affinity w/FcRs, 4 has intermediate aff, 2 has very low aff

2.3 List five areas of the body which are the major portals of entry for microorganisms.

mouth and upper alimentary canal (enzymes, antimicrobial peptides, directional flow to stomach) stomach (low pH, digestive enzymes, antimicrobial peptides) small intestine (digestive enzymes) large intestine (normal intestinal flora compete with invading microbes) airway and lungs (cilia sweep mucus forward, coughing, sneezing expels mucus, macrophages in alveoli of lungs) (skin is a poor portal of entry)

2.2 Describe the role of mucus and skin in preventing pathogen entry. MUCUS

mucosal membranes are lined with epithelium covered with mucus -respiratory, GI, urogenital systems, and the eyes are all common portals of entry -mucus traps entering microbes and then flushes them from the systems of the body by mechanical movement -provide moisture, entrapment, flushing away of microbes -primary portals of entry and exist

MALT

mucosal-associated lymphoid tissue

What is MALT?

mucosal-associated lymphoid tissue of secondary lymphoid organs -mucous membranes lining the digestive, respiratory, and urogenitcal systems, contain organized lymphoid tissues called this

allotype

multiple allelic form of genes in a species responsible for allelic variation; allotypic determinants are minor variations that determine allotype (no change in isotype or function)

Tumor cells express different types of tumor antigens; namely:

mutated self protein that doesn't contribute to tumorigenesis; product of oncogene or mutated tumor suppressor; overexpressed or aberrantly expressed self protein; oncogenic virus

Hyper IgM immunodeficiency

mutation in CD40L: X-linked mutation in CD40; AR

XLA

mutation in gene encoding Btk leads to decrease in serum levels of all immunoglobulins; treatment = IVIG every 3-4 wks for life (generates passive immunity)

What are patients with IFN-gamma receptor defect susceptible do?

mycobacteria infections

what happens when naive B and T cells encounter an antigen?

naïve B and T cells proliferate and differentiate into effector B and T cells AND memory B and T cells.

chemotactic response

neutrophil migration to the source of chemokine

What are major leukocytes of innate immunity?

neutrophils macrophages dendritic cells natural killer cells

types of granulocytes

neutrophils, eosinophils, and basophils, with neutrophils being the most prevalent leukocyte in blood.

Can you elicit an immune response by injecting only hapten?

no, must be injected in combination with a carrier molecule to elicit an immune response

Ab forms ___ bonds with Ag

non-covalent -critically dependent upon the distance between the interacting groups (must be in close proximity before the forces become significant)

Antigenic epitopes are _____ bound to MHC and expressed on the cell surface.

non-covalently

Basophils

non-phagocytic; release histamines; involved in developing allergies

7.1 linkage diequilibrium

non-random association of alleles at different loci, when the frequency of association of different alleles of loci is higher or lower than would be expected if the loci were independent and associated randomly ex: HLA alleles, because HLA genes are located at adjacent loci on the particular region of a chromosomes and presumed to exhibit epistasis with each other or with other genes

Innate immunity

nonspecific first line of defense; buys time for adaptive response to build skin, phagocytes, PRRs, inflammation, fever, complement

what is an immune response

normally a coordinated response against foreign substances carried out by cells and molecules of the immune system The immune system possesses the ability to react to an infinite number of substances, but normally does not react to healthy cells and tissues. Immune repsonse is coordinated, involves a lot of diff. molecules that work together to address anything foreign in /on barriers

Viruses

obligate intracellular parasites (require machinery of host cell to replicate their nucleic acids and synthesize their proteins) enveloped and non-enveloped--both have protein capsid surrounding their DNA or RNA and both have attachment proteins that bind host receptors to gain entry

somatic gene recombination

occurs during maturation in bone marrow/thymus; IgH (whose C region is initially Cmu) and TCRbeta have gene segments VDJ; IgL and TCRalpha have V and J proper fx relies upon recombinase activating genes (RAG1/2) seq: D+J=DJ + V = VDJ

somatic hypermutation

occurs in already rearranged VJ and VDJ segments occurs in germinal centers of the secondary follicle nucleotide substitutions occur at regions encoding the three CDRs with a frequency of one nucleotide substitution for every one-two cell divisions generates antibodies with varying affinities for antigens

Hyperacute graft rejection

occurs in minutes casued by Abs in recipient recognizing antigens on endothelial cells; activates complement and coagulation-->ischemic necrosis

Acute graft rejection

occurs within days to weeks (<6 mo.) active immune response stimulated by graft alloantigens; mediated by Abs and T cells (CD8 directly destroy, CD4 secrete cytokines)

IgD

on B cell membranes; no biological effector function

MHC Class I

on cancer/virus-infected cells; glycoproteins expressed on the surface of all nucleated cells to present antigens to TC cells; α1 and α2 responsible for forming the closed peptide-binding cleft; α3 highly conserved and interacts with CD8 on TC cells. β2 microglobulin expressed on cell surface; if none of these molecules, then no expression of Class I molecules; Ags are endogenous

mucus

on epithelial surfaces, produced by goblet cells; provides moisture and entraps/eliminates pathogens

Bcl-2

oncogene inhibits apoptosis by preventing the release of cytochrome c from mitochondria; only when Ag is present; bax gene does the opposite

7.1 allele

one of two or more alternative forms of a gene that arise by mutation and are found at the same place on a chromosome

affinity maturation

only Abs with high aff to Ag are preferentially selected to survive

Subset of B cells found in marginal zone of spleen

outside follicle in mucosal tissue/peritoneal cavity; self-renewing cells that express BCRs specific for capsular polysacc (T-independent antigens); quickly activated to provide IgM-secreting plasma cells

What molecular fragments are formed by papain digestion of IgG?

papin digestion: three fragments -cleaves above the disulfide bonds joining the H chains two identical fragments are called Fab (fragment, antigen binding) -composed by the L chain and part of the H chain one fragment is called Fc (fragment, crystallizable) -composed of only by H chains

Immunological approaches to cancer:

passive immunization: Abs directed against tumor antigens; blocking growth factor signaling--UNLOCKS ACTIVE IMMUNE RESPONSE active immunization: tumor pulsed DCs, vaccination against oncogenic viruses (HCB, HPV)

____ can induce all four types of hypersensitivity

penicillin

What fragments are formed by pepsin digestion of IgG?

pepsin digestion: one fragment -cleaves below disulfide bonds composed of two Fab-like fragments: F(ab')2 -can bind and precipitate antigens

DTH can be caused by various contact antigens such as ____,_____, and ___.

poison ivy, hair dye, and cosmetics

Dead (inactivated or killed) vaccines

polio, pertussis, diphtheria, hep B

How do B cells produce membrane-bound IgM and IgD?

poly-adenlyation and differential splicing

Specific immune globulin treatments

post-exposure treatment for: Hep B, Tetanus, rabies

Innate immunity

pre-exists in the host before antigen encounter; manifest w/in hours of infection, recognizes general features of groups of microbes or abnormal self-components, and is the same on first and subsequent encounters of the same antigen

IgA

predominant secretory Ig (milk, saliva, tears, mucus); SIgA exists as dimers or tetramers w/ J chain and secretory component (SC) that protects from enzyme digestion once secreted (poly-Ig receptor cleaved from membrane and becomes SC)

before contacting the antigen, the lymphoid follicle is known as this and is composed of follicular dendritic cells and small resting B cells

primary follicle

20.1 Discuss immune responses that prevent virus infection, specifically the role of: NK cells

primary innate responses against viruses (along with IFN-alpha, beta) -respond to IFN-alpha and beta thereby enhancing their activity and ability to kill virus-infected cells

3.16 (2) Discuss primary and secondary lymphoid organs. PRIMARY

primary lymphoid organs = site of lymphocyte maturation thymus, bone marrow

Bone marrow

primary organ for B cell maturation (liver in fetus) -selection process eliminates B cells with self-reactive Ab receptors

Thymus

primary organ for T cell maturation; cortex outside packed with immature lymphocytes=thymocytes; medulla inner sparse with thymocytes immature lymph cell---enters cortex---divides then goes to medulla---mature T cell---leaves thymus

Spleen

produces lymphocytes, filters the blood, stores blood cells, and destroys old blood cells traps blood-borne Ags; Ags and lymphocytes get there through splenic artery -red pulp-has macrophages and RBCs where old RBCs are destroyed -white pulp-PALS with T lymphocytes; Marginal Zone with B cells in 1' follicles

signal joint

products of V(D)J recombination include a signal joint that is later degraded intervening segments between coding joints

SCID: ADA, PNP deficiency

progressive loss of T and, to lesser extent, B cells; decr. cell-mediate and humoral mutation in genes encoding ADA or PNP leads to toxic metabolite accumulation in lymphocytes

What are interferons?

proteins produced naturally by cells in the immune system after exposure to viruses (alpha, beta, gamma) secreted from different types of cells

What are interferons?

proteins produced naturally by cells in the immune system after exposure to viruses (alpha, beta, gamma) secreted from different types of cells made only when needed and increase MHC I expression and activate NK cells

What does "prozone phenomenon" mean? What is its significance in serological testing?

prozone phenomenon: achieving a false negative result in the reaction of antibody and soluble antigen (precipitation reaction) due to the excess of antibodies not allowing the precipitate to form. This is significant in serological testing because the serum must be titered (diluted) to lower concentrations until it reaches an optimal concentration and a precipitate forms.

RAST

quantitation of allergen-specific IgE

RIST

quantitation of serum IgE levels

conserved sequences in regions just upstream or downstream of gene segments that contains a conserved palindromic heptamer sequence and a conserved AT-rich nonamer sequence

recombination signal sequence (RSSs) (this binds to RAG1 and RAG2 to mediate joining of V(D)J gene segments)

21.1 (4) DiGeorge Syndrome (DGS)

recurrent infections, heart defects, characteristic facial features usually though symptoms vary greatly between individuals large deletion from chromosome 22 produced by an error in recombination at meiosis alcohol consumption during early stages of fetal development may be an environmental explanation for the microdeletion deletion means that several genes from this region are not present in DGS patients immune defect is due to loss of a single TBX gene that encodes for transcription factor T-box-1

Describe the two regions of the trabeculae of spleen

red pulp- contains macrophages and red cells, site at which old and defective red cells are destroyed white pulp- surrounds splenic artery forming the periarteriolar lymphoid sheath (PALS) that is populated with mainly T cells

Structure of immunoglobulin

relatively consistent and resembles a "Y", with antigen binding sites at either end of the top of the "Y". Each side of the structure consists of two chains, a light chain and a heavy chain, which are held together with disulfide bonds. The variable portion of the structure is the antigen-binding region; hinge region between the two Fab segments

C3a, C5a, and C5b67 attract large numbers of neutrophils to the site of the immune complex where they...

release lytic enzymes as they attempt to phagocytose the immune complexes causing tissue destruction.

Harmful effects of fluid exudate

release of lysosomal enzymes by inflammmmatory cells.Destruction of normal tissues by enzymes. Swelling and obstruction of ducts, lymphatics or possible ischemic damage (vascular constriction due to inc. pressure)

Parasites

rely on host for survival single cell protozoa (malaria) and multi-cell, multi-organ animals called worms or helminths (pinworm)

What does CD43 do?

required for assembly of actin filaments needed for formation of microvesicles

Oxygen-dependent killing mechanisms

respiratory burst leads to production of reactive oxygen and nitrogen intermediates (ROI/RNI) such as superoxide, peroxide, hypochlorite, nitric oxide

2.13 (2) Discuss humoral immune response and cell-mediated immune response. CELL-MEDIATED

responses mediated by T lymphocytes -T cells have TCR -TCR bind to antigenic epitopes "presented on" MHC of APC -antigen is processed by APC and bound to MHC on the surface of the cell -T cells can recognize epitope only when it is associated with an MHC molecule on the surface of a self-cell (either APC or altered self-cell)

B cells

responsible for humoral immune responses: they give rise to antibodies that combat and prevent infection by extracellular pathogens.

after activation by the antigen, the follicle is known as this, formed by a ring of concentrically packed B lymphocytes surrounding a center called the germinal center where B cells proliferate and differentiate into plasma cells

secondary follicle

3.16 (2) Discuss primary and secondary lymphoid organs. SECONDARY

secondary lymphoid organs = site of lymphocyte activation -lymph nodes -mucosal associated lymphoid tissue (MALT) -spleen

7.1 haplotype

set of alleles present on each chromosome, group of genes within an organism that was inherited together from a single parent

mechanism of V region rearrangement

site-specific recombination with specific conserved sequences

Where are germinal centers?

sites within secondary lymph nodes where mature B lymphocytes proliferate, differentiate, and mature their antibody genes and switch the class of their antibody genes

Anatomical barriers and secretions

skin (breaks) - antimicrobial peptides, fatty acids mouth - enzymes, directional flow toward stomach stomach - acidic environment degrades peptides small intestine - digestive enzymes large intestine - normal flora, expels waste airway/lungs - cilia move mucus outwards

2.2 Describe the role of mucus and skin in preventing pathogen entry. SKIN

skin is a poor portal of entry and is an anatomical barrier -contains microbial peptides, fatty acids in sebum -largest surface area of all organs in body (16% of total body weight) -most infectious agents cannot penetrate skin directly (except blood flukes and nemtodes) and must enter through a wound -keratinocytes produce antimicrobial compounds that are effective against bacteria and fungi, especially when the skin is damaged -microbiota of the skin produce inhibitory fatty acids and other acids that decrease skin pH

Cytokines

small low molecular weight proteins that link innate immunity

4.1 Define hapten

small molecules/compounds that are <10 kDa may bind antibodies but cannot activate B cells on their own when covalently attached to a carrier molecule (macromolecule), an immune response can then be elicited ex: aniline, DNP, or penicililn

What is the role of somatic hypermutation in affinity maturation?

somatic hypermutation provides the diverse antibodies with various affinities to antigens that affinity maturation can stem from (highest affinity options are selected)

2.14 List four characteristics of the adaptive immune response.

specificity (recognition of subtle differences among antigens) memory (second encounter with the same antigen produces a faster response) diversity (heterogeneity) (capable of recognizing billions of uniquely different antigens) recognition of self and non-self (distinguishes foreign from self-antigens)

In add'n to 2 signal requirement for T cell activation:

stabilization by adhesion molecules (LFA-1 integrin on T cell binds integrin ligand ICAM-1 on APC)

Hematopoietic Homeostatic Mechanism

steady state exists at any given time (equilibrium of proliferation/differentiation and apoptosis); done by controlling expression of cytokines and their receptors and through apoptosis

21.1 (4) Reticular dysgenesis

stem cell defect affects maturation of all leukocytes is a general failure of immunity affected children die at a young age defects in components late in the immune system-

Avidity

strength of interaction btwn multiple target subunits and multiple receptor molecules on the cell surface; avidity is orders of magnitude higher than the affinity, due to synergistic binding of multiple subunits, which greatly reduces the chance of target dissociation from the host cell, since all subunits would have to dissociate simultaneously

Adjuvant

substance injected w/ Ag to enhance immune response -not immunogens -forms a complex to slow release of immunogen, increase half-life of vaccine -induces inflammatory response

Cytokines

substances that modulate immune response and are made by specific cells (communication)

MHC Class I

synthesized in RER. *participates in ENDOGENOUS antigen presentation to CD8+ lymphocytes (Cytotoxic lymphocytes).* *ALL NUCLEATED CELLS EXPRESS MHC Class I.*

MHC Class II

synthesized in RER. *participation in EXOGENOUS antigen presentation to CD4+ lymphocytes (TH Cells). * *MHC II are found on macrophages, dendritic cells and B cells.*

Typical manifestations of Type I are ____ and ____

systemic anaphylaxis and localized anaphylaxis

Facts about Systemic anaphylaxis:

systemic anaphylaxis: by drugs, serum, venoms, peanuts - Enter intravenously and cause vascular permeability, smooth muscle contraction, tracheal occlusion, circulatory collapse, and death. This due to mast cell degranulation and general release of histamine. - Food allergy: allergen cross-linking of IgE on mast cells in upper GI tract from ingestion of allergen. Then it diffuses into the blood vessels. *Basophils also play important role in food allergies Disseminated mast cell activation causes both an increase in vascular permeability and widespread smooth muscle contraction. Fluid leaving the blood causes the blood pressure to drop drastically, a condition called anaphylactic shock. Treat with epinephrine

Cell-mediated immunity (CMI)

the arm of the adaptive immune system that combats infection w/ intracellular pathogens; relies on T cells (Th1 and CTLs) Th1: activate macrophages for enhanced destruction of ingested microbes (classical pathway of macrophage activation) CTLs: kill cells w/ microbes in cytosol, whose antigens presented via MHCI; perforin puts hole in cell and granzymes enter to induce apoptosis; kill target cell

What is cross reactivity?

the epitopes between heterophile antibodies are identical or similar (heterophile antibodies being antibodies elicited by one antigen that can cross-react with a second unrelated antigen)

Alternative pathway

the first to be activated first and the most important pathway for defense against microbes; is activated by microbial polysaccharides.

7.1 genotype

the genetic constitution of an individual organism

gamma interferon

the most important macrophage activating cytokine. involved in T cell type 1 cases where macrophage is infected with something it can't kill like a mycobacterium

antigen presentation

the process of T cell activation by which antigenic peptides are displayed on the surface of antigen presenting cells (APCs) for recognition by T cell receptors

summarize the receptor-ligand pairs important for T cell activation

these elements are required for stimulation of the second signal for T cell activation. look at why they are important and what regulated the (PAMPs)

How do MHC I and II molecules know which antigenic peptides to bind?

they bind antigenic peptides to varying degrees depending on how well the peptide fits into the peptide binding groove.

Gram positive bacteria

thick peptidoglycan layer

Gram negative bacteria

thin peptidoglycan layer, lipoprotein; contain an outer membrane containing LPS (aka endotoxin)

Translocation of microbe antigen-->peripheral lymphoid organs

through vasculature, for presentation to B and T lymphocytes; this is done either as diffusing soluble molecules or in association w/ dendritic cells, which ingest these sample in the infected tissue sites

Allograft:

tissue transferred between genetically different individuals of the same species

Isograft:

tissue transferred between genetically identical individuals

Xenograft:

tissue transferred between individuals of different species

Define Autograft:

tissue transferred from one part of the body to another within the same individual

Intravenous immune globulin (IVIG)

treats: B cell immunodeficiencies (XLA, hyper IgM) some autoimmune diseases

Classical pathway

triggered by immune complexes containing IgG, IgM, or C-reactive protein, and is the last to be activated; plays an important role in certain types of autoimmune diseases.

Lectin pathway

triggered by mannose-binding lectin (MBL) and is the second pathway to be activated.

21.2 (2) Discuss the HIV-1 replication cycle

two RNA genomes and reverse transcriptase enzyme (RT) -HIV gp120 binds to CD4 on target cell -fusion of target cell membrane and envelope of virus -nucleocapsid containing viral genome and enzyme enters cell -viral genome and enzymes released following removal of core proteins -RT uses RNA genome to form a cDNA copy (ssRNA--> SSDNA --> dsDNA) -integrase translocates viral dsDNA into the nucleus and integrates into host chromosomal DNA -cDNA copy integrated into host cell chromosome, directing the rest of the viral replication cycle -transcription factors stimulate transcription of proviral DNA into genomic ssRNA and after processing, mRNA -viral RNA exported to cytoplasm -host-cell ribosomes catalyze synthesis of viral precursor proteins -viral protease cleaves precursors into viral proteins -membrane buds out, forming viral envelope -released viral particles complete maturation; cleaved by viral protease into viral particles

Describe the basic structure of IgG.

two identical light (L) chains of about 25,000 MW two identical heavy (H) chains of about 50,000 MW each light chain is bound to a heavy chain by a strong covalent disulfide bond and by a combination of noncovalent weak interactions (ionic interactions, hydrogen bonds, hydrophobic bonds) L-H chains combo linked to an identical combination of L-H chains forming a four-chain structure of Igs (L-H)^2

Structure of MHC Class II molecule

two polypeptides -33 kDa alpha-chain and 28 kDa beta-chain alpha and beta polypeptides exist as a dimer on the cell surface with the peptide binding cleft facing opposite direction peptide binding cleft lacks conserved terminal peptide and forms open pocket peptide-binding region is made of eight anti-parallel beta-strands spanned by two long anti-parallel alpha-helical regions

What are SCID-like deficiencies?

tyrosine kinase (ZAP-70) defect bare-lymphocyte syndrome (Type I) bare-lymphocyte syndrome (Type II)

Class switching in constant region

upon antigenic stimulation-B cells; special sequences upstream of C segment; interleukins play a role

3.10 Define T lymphocyte

used in the cellular immune response -can recognize epitope only when it is associated with an MHC molecule on the surface of a self-cell (either an antigen presenting cell or an altered self-cell), TCR cannot recognize antigen directly -mature in thymus -express antigen binding receptor (TCR) -Class I MHC recognized by Tc, express CD8 -Class II MHC recognized by Th, express CD4

3.10 Define B lymphocyte

used in the humoral immune response can recognize epitope alone activated B cell can become a plasma cell and secretes Ig

Distinction btween type II/III HS-mediated renal disease

using immunofluorescence; type II: detection of patient autoantibodies binding glomerular basement membrane antigens type III: diffused granular staining pattern indicates immune complexes deposited and trapped in glomeruli; seen in SLE

Systemic anaphylaxis:

usually initiated when allergen introduced directly into the blood stream or absobred from the gut or skin - secondary contact with an allergen can lead to respiratory stress and a drop in BP, a state known as anaphylactic shock. - Insect venom, penicillin, shellfish, and nuts have been associated with sys. anaphylaxis.

chain sequencing

variable domain-amino terminal half/variable constant domain-carboxyl terminal half/constant -kappa is 60%, lambda is 40% (single Ig can only contain one type) -isotypes of constant regions include mu, delta, gamma, epsilon, and alpha (determines class of Ab)

Hapten

very small Ag that cannot evoke an immune response alone; can bind to Ab but cannot activate B cells on their own without being covalently bound to carrier (eg. aniline, DNP, penicillin)

Presentation of antigen samples to B cells

via antigen-presenting cells (APCs), or follicular dendritic cells

What are examples of endogenous antigens processed and presented with Class I MHC on the surface of host cells?

virus infected host cells unique proteins synthesized by cancerous cells

What is thymic selection?

when lymphocytes recognize foreign antigens and disregard self-antigens, involves the programmed cell death of cells that -cannot recognize self-MHC molecules and -have high affinity for self-antigens associated to MHC -95-99% of thymocytes die while maturing due to selective processes

immunodeficiencies

when one or more components of the immune system is/are defective

MHC class I and II molecules

where antigenic peptides are loaded within the T cell (depending on the route of antigen capture) and the MHC/peptide complex is displayed on the APC surface.

Secondary lymphoid organs

where lymphocytes gather to contact the various antigen (lymph nodes, spleen, MALTs)

Type III may be localized or generalized depending on ___

where the immune complexes form

Treatment of Eryth. fetalis?

within 24-48 hrs after delivery, administer anti-Rh antibody (Rho-GAM)--> clears out Rh+ fetal cells before memory B cells may develop

Pus

yellowish white opaque creamy matter produced by the process of suppuration consisting of neutrophils (some dead and dying) and tissue debris.

Localized tissue and vascular damage are noticeable ___ hours later with edema and erythema

~4-8

Describe the organization of TCR genes

α and γ chains encode V and J regions (like light); β and δ chains encode V, D, and J regions (like heavy); gene segments are between V and J segments of the α chain except for δ chain; αβ and γδ are located on different chromosomes

Discuss the outcome of productive rearrangement of alpha-chain gene segments

α-chain gene segment deletes δ-chain genes after productive rearrangement so αβ cannot be coexpressed with γδ receptors

Discuss and compare the structure and function of gamma-delta and alpha-beta T cell receptors (TCR)

αβ TCR - lots of CD3 cells and positive for either CD4 or CD8 phenotypes; MHC restriction to Class I and II; ligands are peptide + MHC γδ TCR - low number of CD3 cells; ligand is microbial phospholipid/parasitic antigen; negative for CD4/CD8 phenotypes; secrete cytokines; regulates αβ TCR to site of pathogen invasion

Describe how the TCR-beta chain was identified

αβ receptor analogous to light/heavy Ig chain

Compare TCR diversity and Ig diversity

β chain rearrangement exhibit allelic exclusion (but not α chain rearrangement); TdT addition in all TCR junctions; TCRs have more limited diversity than Ig in CDR1 and CDR2, but higher diversity in CDR3 because more than one D segment can be joined together

Discuss gamma delta-T cells in regards to their location and function

γδ T cells make up less than 5% of peripheral T cells; major T cell type in skin, intestinal and pulmonary epithelia; intraepidermal lymphoctyes on skin are DN; intraepithelial lymphocytes on intestinal epithelia are CD8+; have limited diversity that can bind Ag directly without MHC

Biochemical Events in Mast Cell Activation and Degranulation:

• Activation of Phosphotyrosine Kinase (PTK) • Phospholipase C (PLC) converts Phosphotidyl Inositol-4,5 biphosphate (PIP2) into Diacylglycerol (DAG) and Inositol Triphosphate (IP3) - ER - Ca 2+ • DAG + Ca 2+ ® activates Protein Kinase C (PKC) - necessary for microtubule assembly and fusion of granules with plasma membrane • Calcium channel (15 seconds - methylation of membrane phospholipids) influx of (Ca 2+) • Transient increase of cAMP and immediate drop below base level - necessary for granule release • Microtubule assembly and contraction of microfilaments ( Ca 2+ ) • SNARE (soluble N-ethylmaleimide attachment receptor) is present in both granules and plasma membrane

What is the process of the detailed biochemical mechanism and signaling mechanism involved in mast cell activation and degranulation?

• Allergen crosslinks IgE bound to FcERI on mast/baso • The proteins tyrosine kinase Lyn is associated w/ the cytoplasmic domain of the gamma-chain of FcERI. Cross link of FcERI receptor activates Lyn, phosphorylating ITAMs of the B and Gamma chains --> further phos. rxns involving Lyn, Syk, Fyn, and phospholipase C (PLC) • Phospholipase C (PLC) converts Phosphotidyl Inositol-4,5 biphosphate (PIP2) into Diacylglycerol (DAG) and Inositol Triphosphate (IP3) - ER - Ca 2+ • DAG + Ca 2+ ® activates Protein Kinase C (PKC) - necessary for microtubule assembly and fusion of granules with plasma membrane. Increase in intracellular Ca +PKC = degranulation • Calcium channel (within 15 seconds of receptor activation - methylation of membrane phospholipids--> Calcium channel) influx of (Ca 2+) at 2 min. • Microtubule assembly and contraction of microfilaments ( Ca 2+ ) • SNARE (soluble N-ethylmaleimide attachment receptor) is present on both granules and plasma membrane. Facilitates fusion and exocytosis of primary mediatiors associated with mast cell degran. •Receptor activation -> activation of mitogen-activated protein kinase (MAPK)= cytokine production and activation of phospholipase A2 (PLA2) •PLA2 hydrolyzes membrane phospholipids and converts arachidonic acid into two powerful lipid mediators: prostaglandins and leukotrienes • Transient increase in activity of mem-bound adenylate cyclase = increase of cAMP (rapid peak at 1 min) -> cAMP-dependent protein kinase phosphorylates mem. proteins in granules. Granules fuse with plasma mem. cAMP level drops below base level - necessary for granule release.

MI

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