A&P 2, Exam 3 (Anki)
What are the subacute sensitivities?
- Cytotoxic (type II) reactions - Immune complex (type III) hypersensitivity
he immune system is a ________ rather than ________ Innate & adaptive defenses intertwined Release & recognize many of same defensive molecules
- Functional system - Organ system
Complement activation tremendously amplifies the inflammation response & promotes ________ via ________
- Phagocytosis - Opsinozation
What are the classes of antibodies
Ig M,A,D,G,E
Almost all secondary responses are ________ (antibody class)
IgG
-Antigens widely distributed in body or blood -Insoluble antigen-antibody complexes form -Complexes cannot be cleared from particular area of body -Intense inflammation, local cell lysis, and cell killing by neutrophils -Example: systemic lupus erythematosus (SLE) What is this describing?
Immune complex (type III) hypersensitivity
IFN alpha and beta also activate ________ cells
Natural Killer
Most clone cells become ________ Secrete specific antibodies at rate of 2000 molecules per second for four to five days, then die Antibodies circulate in blood or lymph Bind to free antigens and mark for destruction by innate or adaptive mechanisms
Plasma cells
B cells can ________ antibody classes but retain antigen specificity IgM at first; then IgG
Switch
False: Antibodies inactivate and tag antigens; do not destroy them -Form antigen-antibody (immune) complexes
T or F: Antibodies destroy pathogens
Positive selection: recognizes Self MHC proteins Negative Selection: does NOT recognize self antigens
The important difference in the pressure tests of T cell maturation is
Naturally acquired—response to bacterial or viral infection Artificially acquired—response to vaccine of dead or attenuated pathogens
WHat are the 2 types of active humoral immunity
Filter lymph—macrophages destroy microorganisms and debris -Prevent delivery of harmful microorganisms to blood and other parts of the body Immune system activation—lymphocytes activated and mount attack against antigens -Strategically located sites where lymphocytes encounter antigens
WHat are the lymph node functions?
Engulf antigens Present fragments of antigens on the MHC protein to T cells for recognition
What are Antigen Presenting Cells
Do not activate naive T cells Present antigens to helper T cell to assist own activation (only concerned with own activation)
What are B lymphocytes in regards to APCs
Bind with fragment of protein synthesized in the cell (endogenous antigen) Endogenous antigen is self-antigen in normal cell; a non-self antigen in infected or abnormal cell Crucial for CD8 cell activation Inform cytotoxic T cells of microorganisms hiding in cells (cytotoxic T cells ignore displayed self-antigens) Act as antigen holders; form "self" part that T cells recognize
What are Class I MHC proteins
Found only on dendritic cells, macrophages, & B-cells Bind with fragments of exogenous antigens that have been engulfed and broken down in a phagolysosome Signal CD4 cells that help is required Recognized by helper T cells What is this describing?
What are Class II MHC proteins
Play central role in adaptive immune response -Activate both humoral and cellular arms -Once primed by APC presentation of antigen, they -Help activate T and B cells -Induce T and B cell proliferation -Their cytokines recruit other immune cells Without TH, there is no immune response
What are Helper T cells
specialized lymph capillaries present in intestinal mucosa -Absorb digested fat and deliver fatty lymph (chyle) to the blood
What are Lacteals
widespread in lymphoid organs and connective tissues Present antigens to T cells to activate themselves into voracious phagocytes that secrete bactericidal chemicals
What are Macrophages in regards to APCs
Nonphagocytic large granular lymphocytes Attack cells that lack "self" cell-surface receptors Induce apoptosis in cancer cells & virus-infected cells Secrete potent chemicals that enhance inflammatory response
What are Natural Killer Cells
Clusters of lymphoid follicles In wall of distal portion of small intestine Similar structures are also found in the appendix Peyer's patches and appendix -Destroy bacteria, preventing them from breaching intestinal wall -Generate "memory" lymphocytes
What are Peyer's Patches
Primary T cell response peaks within a week T cell apoptosis occurs between days 7 and 30 -Benefit of apoptosis: activated T cells are a hazard - produce large amount inflammatory cytokines hyperplasia, cancer Effector activity wanes as amount of antigen declines Memory T cells remain and mediate secondary responses
What are T cell proliferation and differentiation characteristics
Immunoglobulins—gamma globulin portion of blood
What are antibodies primarily made of
Substances that can mobilize adaptive defenses and provoke an immune response Targets of all adaptive immune responses Most are large, complex molecules not normally found in body (nonself)
What are antigens
Include interferons and complement proteins Some attack microorganisms directly Some hinder microorganisms' ability to reproduce Useful against viruses What is this describing?
What are antimicrobial cells?
Immunogenicity: ability to stimulate proliferation of specific lymphocytes Reactivity: ability to react with activated lymphocytes and antibodies released by immunogenic reactions Examples: *foreign protein, polysaccharides, lipids, and nucleic acids*
What are characteristics of complete antigens
Small molecules (haptens) not immunogenic by themselves -E.g., peptides, nucleotides, some hormones May be immunogenic if attached to body proteins and combination is marked foreign Cause immune system to mount harmful attack Examples: poison ivy, animal dander, detergents, and cosmetics
What are characteristics of haptens (incomplete antigens
Chemical messengers of immune system Mediate cell development, differentiation, and responses in immune system Include interferons and interleukins
What are cytokines
pierce membranes with antimicrobial peptides found in neutrophils
What are defensins
Dendritic cells phagocytize pathogens, enter lymphatics to present antigens to T cells in lymph node Most effective antigen presenter known Key link between innate and adaptive immunity
What are dendritic Cells
Immune responses to perceived (otherwise harmless) threat cause tissue damage Different types distinguished by -Their time course -Whether antibodies or T cells involved Antibodies cause immediate and subacute hypersensitivities T cells cause delayed hypersensitivity
What are hypersensitivities
Congenital or acquired conditions that impair function or production of immune cells or molecules such as complement or antibodies
What are immunodeficiencies
Family of immune modulating proteins -Have slightly different physiological effects Viral-infected cells secrete IFNs (e.g., IFN alpha & beta) to "warn" neighboring cells -IFNs enter neighboring cells >> produce proteins that block viral reproduction and degrade viral RNA -IFN alpha and beta also activate NK cells
What are interferons
proteins produced by innate system to recognize foreign invaders
What are lectins
Principal lymphoid organs of body Embedded in connective tissue, in clusters along lymphatic vessels Near body surface in inguinal, axillary, and cervical regions of body
What are lymph nodes
Similar to veins, except -Have thinner walls, with more internal valves -Anastomose more frequently Collecting vessels in skin travel with superficial veins Deep vessels of the trunk and digestive viscera travel with arteries Nutrients supplied from branching vasa vasorum
What are lymphatic collecting vessels
Formed by union of largest collecting vessels -Paired lumbar -Paired bronchomediastinal -Paired subclavian -Paired jugular trunks -Single intestinal trunk
What are lymphatic trunks
main warriors of immune system Arise in red bone marrow Mature into one of two main varieties -T cells (T lymphocytes) -B cells (B lymphocytes)
What are lymphocytes roles in the immune system
solid, spherical bodies of tightly packed lymphoid cells and reticular fibers Often have Germinal centers of proliferating (dividing) B cells -May form part of larger lymphoid organs, like lymph nodes -isolated aggregations of Peyer's patches (in the intestinal wall) and in appendix
What are lymphoid follicles (nodules)
Provide structural basis of immune system House phagocytic cells and lymphocytes Structures include spleen, thymus, tonsils, lymph nodes, and other lymphoid tissues
What are lymphoid organs and tissues?
develop from monocytes - chief phagocytic cells - robust cells Free ________ wander through tissue spaces, e.g., alveolar macrophages Fixed ________permanent residents of some organs; e.g., stellate ________(liver) and microglia (brain) What is this describing?
What are macrophages
Protein molecules (self-antigens) on surface of cells not antigenic to self but antigenic to others in transfusions or grafts Example: MHC glycoproteins -Coded by genes of major histocompatibility complex (MHC) and unique to individual Have groove holding self- or foreign antigen -T lymphocytes can only recognize antigens that are presented on MHC proteins -Usually a dendritic cell (major APC) "presents antigens to naïve T cells to activate them.
What are major histocompatibility complex proteins? (MHC)
most abundant leukocyte but die fighting Become phagocytic on exposure to infectious material
What are neutrophils
Dampen immune response by direct contact or by inhibitory cytokines such as IL-10 and TGF-beta Important in preventing autoimmune reactions -Suppress self-reactive lymphocytes in periphery (outside lymphoid organs) -Research into using them to induce tolerance to transplanted tissue
What are regulatory T cells
Most naturally occurring antigens have numerous antigenic determinants that -Mobilize several different lymphocyte populations -Form different kinds of antibodies against them Large, chemically simple molecules (e.g., plastics) have little or no immunogenicity
What are some characteristics of antigenic determinants
Protects against infectious agents and abnormal body cells Amplifies inflammatory response Activates complement Must be primed by initial exposure to specific foreign substance (antigen) -Priming takes time
What are some characteristics of the adaptive defenses
Stores breakdown products of RBCs (e.g., iron) for later reuse Stores blood platelets and monocytes for release into the blood when needed May be site of fetal erythrocyte production (normally ceases before birth) Encased by fibrous capsule; has trabeculae Contains lymphocytes, macrophages, and huge numbers of erythrocytes
What are some functions of the spleen
rejection after 10 years in 50% of patients Cannot protect from foreign agents Chimeric immune system -Suppress recipient's bone marrow -Douse recipient's bone marrow with bone marrow from donor of new organ -"Combined" immune system may treat transplanted organ as self
What are some immunosuppressive therapy problems
Naturally acquired—antibodies delivered to fetus via placenta or to infant through milk Artificially acquired—injection of serum, such as gamma globulin -Protection immediate but ends when antibodies naturally degrade in body
What are the 2 types of passive humoral immunity
1. Classical pathway (innate & adaptive) 2. Lectin pathway (innate immunity) 3. Alternative pathway (innate)
What are the 3 pathways of complement activation
1. Leukocytosis: release of neutrophils from bone marrow in response to leukocytosis-inducing factors from injured cells 2. Margination: neutrophils cling to walls of capillaries in inflamed area in response to CAMs cell adhesion molecules 3. Diapedesis of neutrophils 4. Chemotaxis: inflammatory chemicals (chemotactic agent) promote positive chemotaxis of neutrophils
What are the 4 steps for phagocyte mobilization (know exact order)
Nonspecific cellular and chemical means of protection (necessary if 1st defense mechanism is breached) Phagocytes Natural killer (NK) cells Antimicrobial proteins interferons & complement proteins Fever Inflammatory response macrophages, mast cells, WBCs, & inflammatory chemicals
What are the basic mechanisms of the 2nd defense
T cells -Manage immune response -Attack and destroy infected cells B cells -Produce plasma cells, which secrete antibodies -Antibodies mark antigens for destruction by phagocytosis or other means
What are the basic roles of B and T cells
1. Redness 2. Heat 3. Swelling 4. Pain (Sometimes 5. Impairment of function)
What are the cardinal signs of inflammation
B lymphocytes (B cells)—humoral immunity T lymphocytes (T cells)—cellular immunity Antigen-presenting cells (APCs) -Do not respond to specific antigens -Play essential auxiliary roles in immunity
What are the cells of the adaptive immune system
Each pathway involves activation of proteins in an orderly sequence Each step catalyzes the next Each pathway converges on C3, which cleaves into C3a and C3b Common terminal pathway initiated that -Enhances inflammation, promotes phagocytosis, & causes cell lysis
What are the characteristics of complement activation
Very permeable (take up proteins, cell debris, pathogens, and cancer cells) -Endothelial cells overlap loosely to form one-way minivalves -Anchored by collagen filaments, preventing collapse of lymphatic capillaries; increased ECF volume opens minivalves Pathogens travel throughout body via lymphatics What is this describing?
What are the characteristics of lymphatic capillaries
Neutralization & agglutination (the two most important) Precipitation & complement fixation
What are the defensive mechanisms used by antibodies
Triggered whenever body tissues injured by trauma, intense heat, chemicals, infections -Prevents spread of damaging agents -Disposes of cell debris and pathogens -Alerts adaptive immune system -Sets the stage for repair
What are the functions of inflammatory response
Macrophages phagocytize foreign substances; help activate T cells Dendritic cells capture antigens and deliver them to lymph nodes; activate T cells Reticular cells produce reticular fiber stroma that supports other cells in lymphoid organs
What are the immune and supporting cells?
Kinins, prostaglandins (PGs), & complement proteins -Dilate local arterioles (hyperemia) congested w/ blood -Causes redness and heat of inflamed region Make capillaries leaky Many attract leukocytes to area Some have inflammatory roles
What are the inflammatory mediators
1st Line of Defense - external body membranes; skin & mucosae that lines all body cavities open to the exterior; mechanical/physical & chemical barrier 2nd Line of Defense - antimicrobial proteins, phagocytes, and other cells -Inhibit spread of invaders -Inflammation most important mechanism (hallmark)
What are the lines of defense for innate immunity
Right lymphatic duct drains right upper arm and right side of head and thorax Thoracic duct arises as cisterna chyli; drains rest of body Each empties lymph into venous circulation at junction of internal jugular and subclavian veins on its own side of body
What are the lymphatic ducts?
Lymphatic capillaries Collecting lymphatic vessels Lymphatic trunks and ducts
What are the lymphatic vessels?
Weakly self-reactive lymphocytes may be activated by -Foreign antigens may resemble self-antigens -Antibodies against foreign antigen may cross-react with self-antigen New self-antigens may appear, generated by -Gene mutations -Changes in self-antigens by hapten attachment or infectious damage -Release of novel self-antigens by trauma to barrier
What are the mechanisms of autoimmune diseases
Origin - all originate in red bone marrow Maturation (two-fold selection process) Seeding secondary lymphoid organs & circulation Antigen encounter and activation Proliferation and differentiation
What are the steps of lymphocyte activation
1. Network of lymphatic vessels (lymphatics) 2. Lymph - fluid in vessels 3. Lymph nodes - cleanse lymph
What are the three main parts of the lymphatic system
Cortex Cortex contains follicles with germinal centers, heavy with dividing B cells Deep cortex houses T cells in transit Medulla Medullary cords extend inward from cortex and contain B cells, T cells, and plasma cells Dendritic cells nearly encapsulate follicles T cells circulate continuously among blood, lymph nodes, and lymph Lymph sinuses
What are the two distinct regiuons inside the lymph node
Innate (nonspecific) defense system Adaptive (specific) defense system
What are the two intrinsic systems of the immune system
CD4 and CD8 cells based on which glycoprotein surface receptors displayed
What are the two types of T cells?
Dendritic cells in connective tissues and epidermis Macrophages in connective tissues and lymphoid organs B cells
What are the types of APCs
Autografts: from one body site to another in same person (ideal) Isografts: between identical twins (ideal) Allografts: between individuals who are not identical twins (most common) Xenografts: from another animal species
What are the types of organ transplants
Specific - recognizes and targets specific antigens Systemic - not restricted to initial site Memory - stronger attacks to "known" antigens
What are three unique traits of the adaptive defense
- Genes, not antigens, determine which foreign substances immune system will recognize -Coded for by ~25,000 genes -Gene segments are shuffled by somatic recombination What is this describing?
What determines antigen receptor diversity
CD4 cells usually become helper T cells (TH); activate B cells, other T cells, macrophages, and direct adaptive immune response -Some become regulatory T cells - which moderate immune response Can also become memory T cells
What do CD4 cells become
become cytotoxic T cells (Tc) Destroy cells harboring foreign antigens Also become memory T cells
What do CD8 cells become
Directly attack and kill other cells (Bind to a self-nonself complex ) Activated TC cells circulate in blood and lymph and lymphoid organs in search of body cells displaying antigen they recognize Targets -Virus-infected cells -Cells with intracellular bacteria or parasites -Cancer cells -Foreign cells (transfusions or transplants)
What do cytotoxic T cells (TC) do?
Return interstitial fluid and leaked plasma proteins back to blood ~ 3L/day Once interstitial fluid enters lymphatics, called lymph One-way system; lymph flows toward heart
What do lymphatic vessels do?
Surface barriers ward off invading pathogens Skin, mucous membranes, & their secretions Physical barrier to most microorganisms Keratin resistant to weak acids/bases, bacterial enzymes, & toxins Mucosae provide similar mechanical barriers What is this describing?
What do the surface barriers do in the 1st defense
Secreted by lymphocytes Widespread immune mobilizing effects Activates macrophages
What does IFN gamma do
Increase capillary permeability leading to exudate Fluid containing clotting factors and antibodies Delivers clotting proteins and complement to the interstitial fluid Causes local swelling (edema) Swelling pushes on nerve endings >> pain Pain also from bacterial toxins, prostaglandins, and kinins Moves foreign material into lymphatic vessel
What does edema do in inflammatory response
The cell becomes immunocompetent by recognizing one specific antigen by binding to it. If they can do that and are unresponsive when binding to self antigens and proteins after forming a receptor, then they become immunocompetent. However, they are still naive because they have yet to bind to a foreign antigen and become activated.
What does it mean by having an immunocompetent but naïve B or T lymphocyte?
Protective chemical barrier inhibit or destroy microorganisms -Acidity of skin & secretions - acid mantle - inhibits growth -Enzymes - lysozyme of saliva, respiratory mucus (mucin), & lacrimal fluid - kill many microorganisms -Defensins - broad-spectrum antimicrobial peptide - inhibit growth (increase when surface barriers are breached) -Other chemicals - lipids in sebum, dermcidin in sweat- toxic to bacteria
What does the chemical barrier do in the 1st defense
Begins with "alarm" chemicals released into ECF by injured tissues, immune cells, blood proteins (mast cells) -Macrophages & epithelial cells of boundary tissues bear Toll-like receptors (TLRs): sound the alarm to trigger an immune response -11 types of TLRs recognize specific classes of infecting microbes Activated TLRs trigger release of cytokines that promote inflammation
What does the inflammatory response in the immune system begin wit
Cripples immune system by interfering with activity of helper T cells Characterized by severe weight loss, night sweats, and swollen lymph nodes Opportunistic infections occur, including pneumocystis pneumonia and Kaposi's sarcoma Caused by HIV
What is Acquired Immune Deficiency Syndrome (AIDS)
Lymphoid tissues in mucous membranes throughout body Protects from pathogens trying to enter body Largest collections of MALT in tonsils, Peyer's patches, appendix Also in mucosa of respiratory and genitourinary organs; rest of digestive tract
What is Mucosa-associated Lymphoid Tissue (MALT
genetic defect Marked deficit in B and T cells Defective adenosine deaminase (ADA) enzyme Metabolites lethal to T cells accumulate Fatal if untreated; treated with bone marrow transplants
What is Severe Combined Immunodeficiency (SCID) Syndrome
Slow onset (one to three days) Mechanism depends on helper T cells Cytokine-activated macrophages and cytotoxic T cells cause damage Example: allergic contact dermatitis (e.g., poison ivy) Agents act as haptens The immune system sees them as foreign after they diffuse through the skin and attach to self-proteins TB skin test depends on this reaction
What is a delayed hypersensitivity
Cell hybrids: fusion of tumor cell and B cell Creates pure antibody that proliferates indefinitely and have ability to produce single type of antibody Used in research, clinical testing, and cancer treatment
What is a hybridoma
Helper T cells cause release of enzymes of respiratory burst, which kill pathogens resistant to lysosomal enzymes by (neutrophils also associated) -Releasing cell-killing free radicals -Producing oxidizing chemicals (e.g., H2O2) -Increasing pH and osmolarity of phagolysosome activating digesting enzymes
What is a respiratory burst
When B cells encounter antigens and produce specific antibodies against them
What is active humoral immunity
Systemic response to allergen that directly enters blood and circulates rapidly Basophils and mast cells enlisted throughout body Systemic histamine release may cause -Constriction of bronchioles; tongue may swell -Sudden vasodilation and fluid loss from bloodstream may >> -Circulatory collapse (hypotensive shock) and death
What is anaphylactic shock
Without T cell co-stimulation they: Become tolerant to that antigen Are unable to divide Do not secrete cytokines
What is anergy
Antibodies bind same determinant on more than one cell-bound antigen Cross-linked antigen-antibody complexes agglutinate Example: clumping of mismatched blood cells
What is antibody agglutination
Amplifies inflammatory response Promotes phagocytosis via opsonization >> Positive feedback cycle that enlists more and more defensive elements
What is antibody complement activation
Main antibody defense against cellular antigens (bacteria, mismatched RBCs) Several antibodies bind close together on a cellular antigen complement-binding sites on stem regions align -Triggers complement fixation into cell's surface -Cell lysis
What is antibody complement fixation
Simplest defensive mechanism Antibodies block specific sites on viruses or bacterial exotoxins Prevent these antigens from binding to receptors on tissue cells Antigen-antibody complexes undergo phagocytosis
What is antibody neutralization
Soluble molecules (instead of cells) are cross-linked Complexes precipitate and are subject to phagocytosis Substance becomes solid to remove it
What is antibody precipitation
cell death
What is apoptosis
Immune system loses ability to distinguish self from foreign Production of autoantibodies and sensitized TC cells that destroy body tissues Examples include multiple sclerosis, myasthenia gravis, Graves' disease, type 1 diabetes mellitus, systemic lupus erythematosus (SLE), glomerulonephritis, and rheumatoid arthritis
What is autoimmune disease
Naive lymphocyte's first encounter with antigen >> selected for further development If correct signals present, lymphocyte will complete its differentiation
What is clonal selection in regard to T and B cells
Requires T cell binding to other surface receptors on an APC - co-stimulatory signals -Dendritic cells and macrophages produce surface B7 proteins when innate defenses mobilized -B7 binding crucial co-stimulatory signal Cytokines (interleukin 1 and 2 from APCs or T cells) trigger proliferation and differentiation of activated T cell
What is co-stimulation in T Cell binding
attachment of C3b to a pathogen.
What is complement fixation
lymphoid cells and reticular fibers found in every body organ (Submucosal membrane sites) Larger collections in lamina propria of mucous membranes such as those lining the digestive tract
What is diffuse lymphoid tissue
A fluid rich in protein and cellular elements that oozes out of blood vessels due to inflammation and is deposited in nearby tissues. -Clotting factors and antibodies
What is exudate
Acquired immunodeficiency Cancer of B cells Leads to immunodeficiency by depressing lymph node cells
What is hodgkins disease
transmitted via body fluids—blood, semen, and vaginal secretions HIV enters the body via -Blood transfusions; blood-contaminated needles; sexual intercourse and oral sex; mother to fetus Destroys TH cells >> depresses cellular immunity
What is human immunodeficiency virus (HIV)
Antibodies, produced by lymphocytes, circulating freely in body fluids Bind temporarily to target cell Temporarily inactivate -Mark for destruction by phagocytes or complement Humoral immunity has extracellular targets
What is humoral immunity
Acute (type I) hypersensitivities (allergies) begin in seconds after contact with allergen Initial contact is asymptomatic but sensitizes person Reaction may be local or systemic >> (anaphylactic shock)
What is immediate hypersensitivity
Interleukin 1 (IL-1) released by macrophages co-stimulates bound T cells to Release interleukin 2 (IL-2) Synthesize more IL-2 receptors
What is interleukin 1 (IL-1)
IL-2 key growth factor, acting on cells that release it and other T cells Encourages activated T cells to divide rapidly
What is interleukin 2 (IL-2)
Houses, and provides proliferation site for, lymphocytes Surveillance vantage point for lymphocytes and macrophages Two main types ("packages") -Diffuse lymphoid tissue; Lymphoid follicles What is this describing?
What is lymphoid tissue
Largely reticular connective tissue - type of loose connective tissue Dominates all lymphoid organs except the thymus
What is lymphoid tissue mainly made of
coating by complement proteins or antibodies to mark pathogens
What is opsonization
Readymade antibodies introduced into body B cells are not challenged by antigens Immunological memory does not occur Protection ends when antibodies degrade What is this describing?
What is passive humoral immunity
Monomer or dimer; in mucus and other secretions Helps prevent entry of pathogens Secretory
What is the IgA antibody class
Monomer attached to surface of B cells Functions as B cell receptor
What is the IgD antibody class
Monomer active in some allergies and parasitic infections Causes mast cells and basophils to release histamine
What is the IgE antibody class
Pentamer (larger than others); first antibody released Potent agglutinating agent (clumping) Readily fixes and activates complement
What is the IgM antibody class
Important functions early in life Found in inferior neck; extends into mediastinum; partially overlies heart Increases in size and most active during childhood Stops growing during adolescence, then gradually atrophies -Still produces immunocompetent cells, though slowly
What is the Thymus
Works at the start of the infection, especially bacterial
What is the alternative pathway to complement activation
T- or Y-shaped antibody monomer of four looping polypeptide chains linked by disulfide bonds Two identical heavy (H) chains with hinge region at "middles" Two identical light (L) chains Variable (V) regions at one end of each arm combine to form two identical antigen-binding sites Constant (C) regions of stem -Determine antibody class -Serve common functions in all antibodies by dictating -Cells and chemicals that antibody can bind -How antibody class functions to eliminate antigens
What is the basic antibody structure
Antibodies bind to pathogens surface
What is the classical pathway to complement activation
Unleashes inflammatory chemicals that amplify all aspects of inflammatory response Kills bacteria and certain other cell types by cell lysis Enhances both innate and adaptive defenses Our cells contain complement activation inhibitors (cells circulate in inactive form)
What is the complement system (2nd defense system)
Vary in shape and size but most bean shaped External fibrous capsule Trabeculae extend inward and divide node into compartments
What is the exterior structure of a lymph node
Returns fluids that leaked from blood vessels back to blood
What is the general function of the lymphatic system
Induced by infection & requires some time before it gains strength Activated by lectins binding to specific sugars on microorganisms surface
What is the lectin pathway to complement activation
Phagocyte must adhere to particle -Some microorganisms evade adherence with capsule -Opsonization marks pathogens—coating by complement proteins or antibodies Cytoplasmic extensions from the phagocyte bind to & engulf particle in vesicle called phagosome Phagosome fuses with lysosome >> phagolysosome >> digestion by enzymes >> exocytosis of debris
What is the mechanism of phagocytosis
Cell proliferation & differentiation upon first antigen exposure Lag period: three to six days (need time to generate B cells) Peak levels of plasma antibody are reached in 10 days Antibody levels then declin
What is the primary immune response of immunological memory
Activated lymphocyte proliferates >> exact clones Most clones >> effector cells that fight infections Few remain as memory cells -Able to respond to same antigen more quickly second time B and T memory cells & effector T cells circulate continuously What is this describing?
What is the proliferation and differentiation of T and B cells
1. Cell lysis begins when -C3b binds to target cell >> insertion of complement proteins called membrane attack complex (MAC) into cell's membrane -MAC forms and stabilizes hole (pore) in membrane >> influx of water >> lysis of cell 2. C3b also causes opsonization which enhances phagocytosis 3. C3a and other cleavage products amplify inflammation -Stimulate mast cells and basophils to release histamine which increase capillary permeability -Increase blood flow -Attract neutrophils and other inflammatory cells
What is the result of complement activation
Re-exposure to same antigen gives faster, more prolonged, more effective response Sensitized memory cells respond within hours Antibody levels peak in two to three days at much higher levels Antibodies bind with greater affinity Antibody level can remain high for weeks to months
What is the secondary immune response of immunological memory
Largest lymphoid organ Served by splenic artery and vein, which enter and exit at the hilum Site of lymphocyte proliferation and immune surveillance and response Cleanses blood of aged cells and platelets, macrophages remove debris
What is the spleen
(L&R) Thymic lobules contain outer cortex and inner medulla Most thymic cells are lymphocytes Cortex contains rapidly dividing lymphocytes and scattered macrophages Medulla contains fewer lymphocytes and thymic corpuscles involved in regulatory T cell development (prevent autoimmunity)
What is the structure of the Thymus
Two distinct areas White pulp around central arteries -where immune functions take place -Mostly lymphocytes on reticular fibers Red pulp in venous sinuses and splenic cords -Rich in RBCs and macrophages for disposal of worn-out RBCs and bloodborne pathogens -Composed of splenic cords and sinusoids -Splenic cords separate the blood filled splenic sinusoids
What is the structure of the spleen
Contain follicles with germinal centers Are not fully encapsulated Overlying epithelium invaginates forming tonsillar crypts -Trap and destroy bacteria and particulate matter -Allow immune cells to build memory for pathogens
What is the structure of tonsils?
grouped at base of tongue
Where are Lingual Tonsils
in posterior wall of nasopharynx Referred to as adenoids if enlarged
Where are Pharyngeal Tonsils
surrounding openings of auditory tubes into pharynx
Where are Tubal Tonsils
Absent from bones, teeth, bone marrow, and CNS
Where are lymphatic capillaries NOT located
B cells stay in the bone marrow (Primary Lymphoid Organ) T cells mature in the thymus (Primary Lymphoid Organ) -All other lymphoid organs are known as secondary Both originate in the red bone marrow
Where do T and B cells mature
Type I MHC: CD8 cell (all cells except RBCs) Type II MHC: CD4 cell (Only APCs)
Which type of MHC is recognized by T cells and what cells constitute each type
nucleic acid surrounded by a protein envelope- lacks cellular machinery to generate ATP or protein synthesis Virally infected cells can't do much to save themselves BUT can secrete IFN (interferon) What is this describing?
a virus
Helper, cytotoxic, & regulatory T cells are ________ Naive T cells simply termed CD4 or CD8 cells
activated T cells
Proteins secreted by plasma cells Capable of binding specifically with antigen detected by B cells Grouped into one of five Ig classes What is this describing?
antibodies
T and B cells protect against ________ Anything body perceives as foreign Bacteria and bacterial toxins, viruses, mismatched RBCs, cancer cells
antigens
Where are Palatine tonsils
at posterior end of oral cavity Largest; often become infected
Lymphocytes act against target cell -Directly - by killing infected cells -Indirectly - by releasing chemicals that enhance inflammatory response; or activating other lymphocytes or macrophages ________ has cellular targets What is this describing?
cellular immunity
What is the function of the TH2 helper T cell?
defend against parasitic worms; mobilize eosinophils; promote allergies
IFNs have an indirect role in ________
fighting cancer
T and B cells are seeded to secondary lymphoid organs in order to ________
increase chance of encounter with antigen
Antibodies do not ________ unless lesion present Can act intracellularly if attached to virus before it enters cell
invade solid tissue
What is the function of the TH17 helper T cell?
link adaptive and innate immunity by releasing IL-17; may play role in autoimmune disease
What do lymph sinuses contain
macrophages
The complement protein C3b stimulates ________, and enhances inflammation
mast cells and basophils to release histamine
What is the function of the TH1 helper T cell?
mediate most aspects of cellular immunity
Clone cells that do not become plasma cells become ________ Provide immunological memory Mount an immediate response to future exposures to same antigen
memory cells
Immunocompetent (matured) B and T cells not yet exposed to antigen called ________
naive
What are the phagocytes in the 2nd defense system
neutrophils and macrophages
The complement protein C3b causes ________, and enhances phagocytosis
opsonization
What are antigen determinants
parts of an antigen that allow lymphocyte or antibody receptors to bind to them (immunogenic)
What are the steps of the interferon mechanism against viruses (short answer)
1. Virus enters cell 2. interferons genes switch on 3. cell produces interferon molecules 4. Interferon is released and binds to a neighboring cell which stimulates the cell to turn on genes for antiviral proteins 5. Antiviral genes in neighboring cell block reproduction of the virus when it enters
Recognize antigens by binding to them Communicate with one another so that whole system mounts specific response Use lymphocytes, APCs, and specific molecules to identify and destroy nonself substances
Adaptive immunity depends on its cells ability to
he adaptive immune system is ________ Specialized, not generalized
specific
Monomer; 75-85% of antibodies in plasma Main antibody from secondary & late primary responses Crosses placental barrier which Ig antibody class is this describing?
the IgG antibody class
What are the two types of MHC cells important to T cell activation?
Class I MHC proteins Class II MHC proteins Both types are synthesized at ER and bind to peptide fragments
-Antibodies bind to antigens on specific body cells, stimulate phagocytosis and complement-mediated lysis of cellular antigens -Example: mismatched blood transfusion reaction What is this describing?
Cytotoxic (type II) reactions
Adaptive defense system (specific) attacks particular foreign substances Takes longer to react than innate system What is this describing?
the tonsils
Enters convex side (think bean shape) via afferent lymphatic vessels; travels through large subcapsular sinus and smaller sinuses to medullary sinuses; exits concave side at hilum via efferent vessels Fewer efferent vessels so flow somewhat stagnates; allows lymphocytes and macrophages time to function
Describe the circulation of lymph in the lymph nodes
Adaptive defense system (specific) attacks particular foreign substances Takes longer to react than innate system Which defense system (in number order) is this describing?
third line of defense for the immune system
Class I: Endogenous (intracellular pathogens or proteins made by cancerous cells) Class II: Exogenous (phagocytized extracellular pathogens)
Foreign antigens on MHC proteins are
________ is a two-step process -Antigen binding -Co-stimulation: B7 protein "double handshake" Both occur on surface of same APC Both required for clonal selection What is this describing?
How are T Cells activated
Immunocompetence - lymphocyte can recognize one specific antigen by binding to it -B or T cells display only one unique type of antigen receptor on surface when achieve maturity - bind only one antigen Self-tolerance -Lymphocytes unresponsive to own antigens
How are T and B cells educated
Soon after inflammation begins phagocytes flood the damaged area Neutrophils lead; macrophages follow -As attack continues, monocytes arrive -12 hours after leaving bloodstream >> macrophages -These "late-arrivers" replace dying neutrophils and remain for clean up prior to repair If inflammation due to pathogens, complement activated; adaptive immunity elements arrive
How are phagocytes mobilized
Dendritic cells engulf dying virus-infected or tumor cells, or import antigens via temporary gap junctions with infected cells—then display both class I and class II MHCs
How do APCs get endogenous antigens from another cell and display them on class I MHCs?
B cells may be activated without TH cells by binding to T cell-independent antigens -Response weak and short-lived Most antigens require TH co-stimulation to activate B cells: T cell-dependent antigens
How do B cells activate without T helper cell
________ mature in red bone marrow Positively selected if successfully make antigen receptors Those that are self-reactive (high affinity to self) are eliminated by apoptosis (clonal deletion)
How do B cells mature
Recognize other signs of abnormality -Lack of class I MHC -Antibody coating target cell -Different surface markers of stressed cells What is this describing?
How do NK cells attack?
Lethal hit - two methods: TC cell releases perforins and granzymes by exocytosis -Perforins create pores through which granzymes enter target cell -Granzymes stimulate apoptosis TC cell binds specific membrane receptor on target cell, and stimulates apoptosis
How do T Cytotoxic cells attack?
T cells mature in thymus under positive & negative selection pressures ("tests") Positive selection -Selects only the T cells that are able to recognize self-MHC proteins; failures destroyed by apoptosis Negative selection -Prompts apoptosis of T cells that bind to self-antigens displayed by self-MHC -Ensures self-tolerance (keep the ones that do NOT recognize self)
How do T cells mature
respond only to processed fragments of antigens displayed on surfaces of cells Antigen presentation vital for activation of naive T cells & normal functioning of effector T cells
How do T cells respond to the immune system?
Amplify responses of innate immune system Activate macrophages >> more potent killers Mobilize lymphocytes and macrophages and attract other types of WBCs
How do T helper cells interact with immunity besides CD4 and CD8
Interact directly with B cells displaying antigen fragments bound to MHC II receptors Stimulate B cells to divide more rapidly and begin antibody formation (releases ILs) What is this describing?
How do helper T cells activate CD4 cells
CD8 cells require TH cell activation into destructive cytotoxic T cells Cause dendritic cells to express co-stimulatory molecules required for CD8 cell activation (IL-2)
How do helper T cells interact with CD8 cells
Oxygen and Nurtients are supplied from branching vasa vasorum.
How do lymphatic vessels obtain oxygen and nutrients from the vascular system?
Most of dead or attenuated (weakened) pathogens Spare us symptoms of primary response Provide antigenic determinants that are both immunogenic (stimulate lymphocytes) & reactive (ability to activate a response)
How do vaccines help in artificially acquired humoral immunity
Causes liver and spleen to sequester iron and zinc (needed by microorganisms) so inhibits bacterial growth Increases metabolic rate >> faster repair
How does a fever benefit other parts of the immune system
Abnormally high body temperature Systemic response to invading microorganisms Leukocytes and macrophages exposed to foreign substances secrete pyrogens Pyrogens act on body's thermostat in hypothalamus, raising body temperature What is this describing?
How does fever play a role in immune system
Has no follicles because it lacks B cells Does not directly fight antigens -Functions strictly in T lymphocyte maturation -Kept isolated via blood thymus barrier Stroma of epithelial cells (not reticular fibers) -Provide environment in which T lymphocytes become immunocompetent
How does the Thymus differ from other lymphoid organs
Mucus-coated hairs in nose Cilia of upper respiratory tract sweep dust- & bacteria-laden mucus toward mouth
How does the respiratory system aid in the 1st defense
Milking action of skeletal muscle Pressure changes in thorax during breathing Valves to prevent backflow Pulsations of nearby arteries Contractions of smooth muscle in walls of lymphatics
How is lymph transported?
What are the two arms of the adaptive defenses
Humoral (antibody-mediated) immunity [extracellular]; use B cells Cellular (cell-mediated) immunity [intracellular]; use T cells
