Immunobiology chapters 1-6

Compare and contrast the 4 types of antigen-binding molecules used by the immune system-antibodies, T-cell receptors, class I MHC molecules, and class II MHC molecules-- in terms of the following characteristics: a) Specificity for antigen b) Cellular expression c) Types of antigen recognized

(a) Both antibodies and T-cell receptors display fine specificity for antigen; very small modifications in an antigen can prohibit its binding to its corresponding antibody or T-cell receptor. MHC molecules do not possess such fine specificity, and a variety of unrelated peptide antigens can be bound by the same MHC molecule. (b) Antibodies are expressed only by the cells of the B-cell lineage; T-cell receptors are expressed by the cells of the T-cell lineage; class I MHC molecules are expressed by virtually all nucleated cells; class II MHC molecules are expressed only by specialized cells that function as antigen-presenting cells (e.g., B cells, macrophages, and dendritic cells). (c) Antibodies can bind to protein or polysaccharide antigens; T-cell receptors recognize only peptides associated with MHC molecules; MHC molecules bind only to processed peptides.

Adaptive immune responses exhibit four immunologic attributes:

1) specificity 2) diversity 3) memory 4) self-nonself recognition

cytotoxic T lymphocytes (CTLs)

A T cell that is antigen-specific and is able to search out and kill specific types of virus-infected cells. When cytotoxic T-lymphocytes (CTLs) find cells carrying the viral peptide they are looking for, they induce these cells to secrete proteins that attract nearby macrophages (a type of white blood cells). These macrophages then surround and destroy the infected cells. CTLs are important in the body's response to viruses and cancer.

mast cells

A bone-marrow-derived cell present in a variety of tissues that resembles peripheral blood basophils, bears fc receptors for IgE, and undergoes IgE-mediated degranulation.

lymphoid progenitor cell

A cell committed to the lymphoid lineage from which all lymphocytes arise.

differentiation antigens

A cell surface marker that is expressed only during a particular developmental stage or by a particular cell lineage.

myeloid progenitor cell

A cell that gives rise to cells of the myeloid lineage.

follicular dendritic cells

A cell with extensive dendritic extensions that is found in the follicles of lymph nodes. Although they do not express MHC class II molecules, they are richly endowed with receptors for complement and Fc receptors for antibody. They are of a lineage that is distinct from MHC class II-bearing dendritic cells.

antibody-dependant cell-mediated cytotoxicity (ADCC)

A cell-mediated reaction in which nonspecific cytotoxic cells that express Fc receptors (e.g., NK cells, neutrophils, macrophages) recognize bound antibody on a target cell and subsequently cause lysis of the target cell.

neutrophil

A circulating, phagocytic, granulocyte involved early in the inflammatory response. It expressed Fc receptors and can participate in antibody-dependent cell-mediated cytotoxicity. Neutrophils are the most numerous white blood cells in the circulation.

Natural killer (NK) cells

A class of large, granular, cytotoxic lymphocyte that do not have T- or B-cell receptors. They are antibody-independent killers of tumor cells and also can participate in antibody-dependent cell-mediated cytotoxicity.

periarteriolar lymphoid sheath (PALS)

A collar of lymphocytes encasing small arterioles of the spleen

cluster of differentiation (CD)

A collection of monoclonal antibodies that all recognize an antigen found on a particular differentiated cell type or types. Each of the antigens recognized by such a collection of antibodies is called a CD marker and assigned a unique identifying number.

marginal zone

A diffuse region of the spleen, situated on the periphery of the PALS, between the red pulp and white pulp that is rich in B cells and contains lymphoid follicles, which can develop into germinal centers.

CD8

A dimeric protein that serves as a coreceptor on MHC class I restricted T cells. Most cytotoxic T cells are CD8+.

GATA-2 gene

A gene encoding a transcription factor that is essential for the development of several hematopoietic cell lineages, including the lymphoid, erythroid, and myeloid lineages.

severe combined immunodeficiency (SCID)

A genetic defect in which immune responses do not occur because of a lack of T cells and possibly B and NK cells.

CD4

A glycoprotein that serves as a co-receptor on MHC class II restricted T cells. Most helper T cells are CD4.

B lymphocytes (B cells)

A lymphocyte that matures in the bone marrow and expresses membrane-bound antibody. After interacting with antigen, it differentiates into antibody-secreting plasma cells and memory cells.

T lymphocytes (T cells)

A lymphocyte that matures in the thymus and expresses a T-cell receptor, CD3, and CD4 or CD8. Several distinct T-cell populations are recognized.

NK1-T cell

A lymphocyte with some of the characteristics of T cells (it has T-cell receptors) as well as those of natural killer cells.

primary follicle

A lymphoid follicle, prior to stimulation with antigen, that contains a network of follicular dendritic cells and small resting B cells.

monocytes

A mononuclear phagocytic leukocyte that circulates briefly in the bloodstream before migrating into the tissues where it becomes a macrophage.

stromal cells

A nonhematopoietic cell that supports the growth and differentiation of hematopoietic cells.

basophil

A nonphagocytic granulocyte that expresses Fc receptors for IgE. Antigen-mediated cross-linkage of bound IgE induces degranulation of basophils.

Pathogen

A pathogen or infectious agent is a biological agent that causes disease or illness to its host.

CD3

A polypeptide complex containing 3 dimers; T-cell co-receptor helps to activate the cytotoxic T-Cell. It consists of a protein complex and is composed of four distinct chains. In mammals, the complex contains a CD3γ chain, a CD3δ chain, and two CD3ε chains. These chains associate with a molecule known as the T-cell receptor (TCR) and the ζ-chain (zeta-chain) to generate an activation signal in T lymphocytes. The TCR, ζ-chain, and CD3 molecules together comprise the TCR complex.

secondary follicle

A primary follicle after antigenic stimulation; it develops into a ring of concentrically packed B cells surrounding a germinal center.

thymus

A primary lymphoid organ, where T-cell maturation takes place.

lymphoblasts

A proliferating lymphocyte.

Antibody molecule

A protein (immunoglobulin), consisting of 2 identical heavy chains and 2 identical light chains that recognizes a particular epitope on an antigen and facilitates clearance of that antigen. Membrane-bound antibody is expressed by B cells that have not encountered antigen; secreted antibody is produced by plasma cells. Some antibodies are multiples of the basic four chain structure.

germinal center

A region within lymph nodes and the spleen where B-cell activation, proliferation, and differentiation occurs. Germinal centers are sites of intense B cell somatic mutation and selection.

chemokines

A restricted class of cytokines that have chemotactic activity and recruit specific cells to the site of the cell secreting that cytokine; Any one of numerous secreted, low molecular-weight polypeptides that mediate chemotaxis for different leukocytes and regulate the expression and/or adhesiveness of leukocyte integrins.

spleen

A secondary lymphoid organ where old erythrocytes are destroyed and blood-borne antigens are trapped and presented to lymphocytes in the PALS and marginal zone.

lymph nodes

A small secondary lymphoid organ that contains lymphocytes, macrophages, and dendritic cells and serves as a site for foreign antigen and for activation and proliferation of lymphocytes.

stem cells

A stem from which differentiated cells derive. Stem cells are classified as totipotent, pluripotent, multipotent, or unipotent depending on the range of cell types that they can generate.

opsonin

A substance (e.g., an antibody or C3b) that promotes the phagocytosis of antigens by binding to them

Ikaros

A transcription factor required for the development of all lymphoid cell lineages.

T regulatory (Treg) cells

A type of T cell that carries CD4 on its surface and is distinguished from TH cells by surface markers, such as CD25, associated with its stage of activation.

leukocytes (white blood cells)

A white blood cell. The category includes lymphocytes, granulocytes, platelets, monocytes, and macrophages.

adaptive immunity (acquired)

Adaptive immunity refers to antigen-specific immune response. The adaptive immune response is more complex than the innate. The antigen first must be processed and recognized. Once an antigen has been recognized, the adaptive immune system creates an army of immune cells specifically designed to attack that antigen.

leukocytosis

An abnormally large number of leukocytes, usually associated with acute infection. Counts greater than 10,000/mm3 may be considered leukocytosis.

chemotactic factors

An agent that can cause leukocytes to move up its concentration gradient.

hematopoietic-inducing microenvironment (HIM)

An anatomical site that contains all of the cells and cellular factors required for the generation and development of blood cells.

Antibody

An antibody (Ab), also known as an immunoglobulin (Ig), is a large, Y-shaped protein produced mainly by plasma cells that is used by the immune system to identify and neutralize pathogens such as bacteria and viruses.

memory B cells

An antigen-committed, persistent B cell. B-cell differentiation results in formation of plasma cells, which secrete antibody, and memory cells, which are involved in the secondary responses

high endothelial venules (HEV)

An area of capillary venule composed of specialized cells with a plump, cuboidal ("high") shape through which lymphocytes migrate to enter various lymphoid organs.

anaphylaxis

An immediate type I hypersensitivity reaction which is triggered by IgE-mediated mast cell degranulation. Systemic anaphylaxis leads to shock and is often fatal. Localized anaphylaxis involves various types of atopic reactions.

Programmed cell death

An induced and ordered process in which the cell actively participates in bringing about its own death.

phagolysosome

An intracellular body formed by the fusion of a phagosome with a lysosome.

T-cell receptor (TCR)

Antigen-binding molecule expressed on the surface of T cells and associated with CD3. It is a heterodimer consisting of either an alpha or beta chain or a gamma and delta chain

effector cells

Any cell capable of mediating an immune function (e.g., activated TH cells, CTLs and plasma cells).

immunodeficiency

Any deficiency in the immune response. It may result from a defect in phagocytosis, the humoral response, or the cell-mediated response. Combined immunodeficiencies affect both the humoral and cell-mediated immune response.

granulocytes

Any leukocyte that contains cytoplasmic granules, particularly the basophil, eosinophil, and neutrophil.

cytokines

Any one of numerous secreted, low molecular-weight proteins that regulate the intensity and duration of the immune response by exerting a variety of effects on lymphocytes and other immune cells. The cytokines react with receptors on various cell types and signal the cell to perform functions such as synthesis of new factors or to undergo differentiation to a new cell type

There are 3 types of lymphoid cells:

B cells, T cells, and NK cells. Only B and T cells are members of clonal populations distinguished by antigen receptors of unique specificity. B cells synthesize and display membrane antibody, and T cells synthesize and display T-cell receptors.Most NK cells do not synthesize antigen-specific receptors, although a small subpopulation of this group, NK-T cells, do synthesize and display a T cell receptor.

dendritic cell (DC)

Bone-marrow-derived cells that descend through the myeloid and lymphoid lineages and are specialized for antigen presentation to helper T cells.

cell-mediated immunity

Cell mediated immunity is an immune response that does not involve antibodies, but rather involves the activation of phagocytes, antigen-specific cytotoxic T-lymphocytes, and the release of various cytokines in response to an antigen.

Fc receptor (FcR)

Cell surface receptor specific for the Fc portion of certain classes of immunoglobulin. It is present on lymphocytes, mast cells, macrophages, and other accessory cells.

clone

Cells arising from a single progenitor cell.

clonal-selection theory

Clonal selection theory is a scientific theory in immunology that explains the functions of cells (lymphocytes) of the immune system in response to specific antigens invading the body. The concept was introduced by an Australian doctor Frank Macfarlane Burnet in 1957 in an attempt to explain the formation of a diversity of antibodies during initiation of the immune response. The theory has become a widely accepted model for how the immune system responds to infection and how certain types of B and T lymphocytes are selected for destruction of specific antigens. The theory states that in a pre-existing group of lymphocytes (specifically B cells), a specific antigen only activates (i.e. selection) its counter-specific cell so that particular cell is induced to multiply (producing its clones) for antibody production. This activation occurs in secondary lymphoid organs such as the Spleen and the Lymph Nodes. In short the theory is an explanation of the mechanism for the generation of diversity of antibody specificity. The first experimental evidence came in 1958, when Gustav Nossal and Joshua Lederberg showed that one B cell always produces only one antibody. The idea turned out to be the foundation of molecular immunology, especially in adaptive immunity.

DiGeorge's syndrome

Congenital thymic aplasia caused by deletion of a sequence on chromosome 22 during embryonic life. Consequences include immunodeficiency, facial abnormalities, and congenital heart disease.

Give examples of mild and severe consequences of immune dysfunction. What is the most common cause of immunodeficiency throughout the world today?

Consequences of mild forms of immune dysfunction include sneezing, hives, and skin rashes caused by allergies. Asthma and anaphylactic reactions are more severe consequences of allergy and can result in death. Consequences of severe immune dysfunction include susceptibility to infection by a variety of microbial pathogens if the dysfunction involves immunodeficiency, or chronic debilitating diseases, such as rheumatoid arthritis, if the dysfunction involves autoimmunity. The most common cause of immunodeficiency is infection with the retrovirus HIV-1, which leads to AIDS.

immunocompetent

Denoting a mature lymphocyte that is capable of recognizing a specific antigen and mediating an immune response.

opsonization

Deposition of opsonins on an antigen, thereby promoting a stable adhesive contact with an appropriate phagocytic cell.

effector response

Effector response is the phenomenon that occurs after the immune system recognizes a foreign organism. A variety of cells and molecules are then recruited to mount an appropriate response to eliminate or neutralize the organism.

endocytosis

Endocytosis is a form of active transport in which a cell transports molecules (such as proteins) into the cell (endo- + cytosis) by engulfing them in an energy-using process.

interstitial fluid

Fluid found in the spaces between cells of an organ or tissue.

class II MHC molecules

Heterodimeric membrane proteins that consist of a noncovalently associated alpha and beta chain, both encoded in the MHC. They are expressed by antigen-presenting cells and function to present antigen to CD+T cells. The classical class II molecules are H-2 IA and IE in mice and HLA-DP in mice and HLA-DP, -DQ, and -DR in humans.

class I MHC molecules

Heterodimeric membrane proteins that consist of an alpha chain encoded in the MHC associated noncovalently with Beta2 microglobulin. They are expressed by nearly all nucleated cells and function to present antigen to CD8+ T cells. The classical class I molecules are H-2 K, D, and L in mice and HLA-A, -B, and -C in humans.

nude mice

Homozygous genetic defect (nu/nu) carried by an inbred mouse strain that results in the absence of the thymus and consequently a marked deficiency of T cells and cell-mediated immunity. The mice are hairless (hence the name) and can accept grafts from other species.

humoral immunity

Humoral immunity, also called the antibody-mediated beta cellularis immune system, is the aspect of immunity that is mediated by macromolecules (as opposed to cells) found in extracellular fluids such as secreted antibodies, complement proteins, and certain antimicrobial peptides.

secondary response

Immune response following exposure to previously encountered antigen; the secondary response occurs more rapidly and is in greater magnitude and duration than the primary response.

Primary response

Immune response following initial exposure to antigen; this response is characterized by short duration and low magnitude compared to response following subsequent exposures to the same antigen

gamma globulin/immunoglobulin

Immunoglobulins, also known as antibodies, are glycoprotein molecules produced by plasma cells (white blood cells). They act as a critical part of the immune response by specifically recognizing and binding to particular antigens, such as bacteria or viruses and aiding in their destruction.

antigenic peptides

In general, a peptide capable of raising an immune response, for example, in a peptide that forms a complex with MHC that can be recognized by a T-cell receptor

Innate and adaptive immunity act in cooperative and interdependent ways to protect the host. Discuss the collaboration of these 2 forms of immunity.

Innate and adaptive immunity cooperate to give a complete protective response against pathogens. An example is the phagocytic cell, which takes up foreign material and processes it to form peptide antigens that are presented by the phagocyte. The presented antigens stimulate T cells that either provide help to B cells for production of antibody or stimulate cytotoxic T cells to provide protection against infected or cancerous cells. In addition, the phagocytic cells take part in inflammation, producing cytokines that attract T cells and B cells to the site.

Innate immunity

Innate immunity refers to nonspecific defense mechanisms that come into play immediately or within hours of an antigen's appearance in the body. These mechanisms include physical barriers such as skin, chemicals in the blood, and immune system cells that attack foreign cells in the body.

innate immunity

Innate immunity refers to nonspecific defense mechanisms that come into play immediately or within hours of an antigen's appearance in the body. These mechanisms include physical barriers such as skin, chemicals in the blood, and immune system cells that attack foreign cells in the body.

lymph

Interstitial fluid derived from blood plasma that contains a variety of small and large molecules, lymphocytes, and some other cells. It circulates through the lymphatic vessels.

signaling

Intracellular communication initiated by receptor-ligand interaction

phagosome

Intracellular vacuole containing ingested particulate materials; formed by the fusion of pseudopodia around a particle undergoing phagocytosis.

Why was Jenner's vaccine superior to previous methods for conferring resistance to smallpox?

Jenner's method of using cowpox infectection to confer immunity was superior to earlier methods because it carried a significantly lower risk of serious disease. The earlier method of using material from lesions of smallpox victims conferred immunity but at the risk of acquiring the potentially lethal disease.

peyer's patch

Lymphoid follicles situated along the wall of the small intestine that trap antigens from the gastrointestinal tract and provide sites where B and T cells interact with antigen.

mucosa-associated lymphoid tissue (MALT)

Lymphoid tissue situated along the mucus membranes that line the digestive, respiratory, and urogenital tracts.

pseudopodia

Membrane protrusions that extend from motile and phagocytosing cells.

collectins

Molecules that have surfactant qualities and can lyse bacterial cell walls. are a part of the innate immune system.

macrophages

Mononuclear phagocytic leukocyte that plays roles in adaptive and innate immunity. There are many types of macrophages, some are migratory, whereas others are fixed in tissues.

apoptosis

Morphologic changes associated with programmed cell death, including nuclear fragmentation, blebbing, and release of apoptotic bodies, which are phagocytosed. In contrast to necrosis, it does not result in damage to surrounding cells.

necrosis

Morphologic changes that accompany death of individual cells or groups of cells that release large amounts of intracellular components to the environment, leading to the destruction and atrophy of tissue.

eosinophil

Motile, somewhat phagocytic granulocytes that can migrate from blood to tissue spaces. They have large numbers of IgE receptors and are highly granular. They are thought to play a role in the defense against parasitic organisms such as roundworms.

extravasation

Movement of blood cells through an unruptured vessel wall into the surrounding tissue, particularly at sites of inflammation.

Opportunistic infections

Opportunistic infections (OIs) are infections that occur more frequently and are more severe in individuals with weakened immune systems, including people with HIV

secondary lymphoid organs

Organs and tissues in which mature, immunocompetent lymphocytes encounter trapped antigens and are activated into effector cells. In mammals, the lymph nodes, spleen, and mucosal-associated lymphoid tissue (MALT) constitute the secondary lymphoid organs.

primary lymphoid organs

Organs in which lymphoid precursors mature into antigenically committed, immunocompetent cells. In mammals, the bone marrow and thymus are the primary lymphoid organs in which B-cell and T-cell maturation occur, respectively.

red pulp

Portion of the spleen consisting of a network of sinusoids populated by macrophages and erythrocytes. It is the site where old and defective red blood cells are destroyed.

white pulp

Portion of the spleen that surrounds the arteries, forming a periarteriolar lymphoid sheath (PALS) populated mainly by T cells.

exocytosis

Process by which cells release molecules (e.g., cytokines, lytic enzymes, degradation products) contained within a membrane-bound vesicle by fusion of the vesicle with the plasma membrane.

major histocompatibility complex (MHC) molecules

Proteins encoded by the major histocompatibility complex and classified as class I, class II, and class III MHC molecules.

The sizes of B-cell epitopes range widely.

Some are quite small (e.g., small peptides or small organic molecules), and are often bound in narrow grooves or deep pockets of the antibody. Protein B-cell epitopes are much larger and interact with a larger, flatter complementary surface on the antibody molecule.

M cells

Specialized cells of the intestinal mucosa and other sites, such as the urogenital tract, that deliver antigen from the apical face of the cell to lymphocytes clustered in the pocket of its basolateral face.

intraepidermal lymphocytes

T cells found in the epidermal layers.

T helper (TH) cells

T cells that are stimulated by antigen to provide signals that promote immune responses.

T cytotoxic cells (Tc)

T cells that kill target cells in an antigen-specific manner

Adaptive immunity exhibits 4 characteristic attributes, which are mediated by lymphocytes. List these 4 attributes and briefly explain how they arise.

The 4 immunological attributes are specificity, diversity, memory, and self/nonself recognition. Specificity refers to the ability of certain membrane-bound molecules on a mature lymphocyte to recognize only a single antigen (or small number of closely related antigens). Rearrangement of the immunoglobulin genes during lymphocyte maturation gives rise to antigenic specificity; it also generates a vast array of different specificities, or diversity, among mature lymphocytes. The ability of the immune system to respond to nonself-molecules, but (generally) not to self-molecules, results from the elimination during lymphocyte maturation of immature cells that recognize self-antigens. After exposure to a particular antigen, mature lymphocytes reactive with that antigen proliferate and differentiate, generating a larger population of memory cells with the same specificity; this expanded population can respond more rapidly and intensely after a subsequent exposure to the same antigen, thus displaying immunologic memory.

Did the treatment for rabies used by Pasteur confer active or passive immunity to the rabies virus? Is there any way to test this?

The Pasteur method for treating rabies consists of a series of innoculations with attenuated rabies virus. This process actively immunizes the recipient who then has anti-rabies to stop the progress of infection. A simple test for active immunity would be to look for anti-rabies antibodies in the recipient's blood at a time after completion of treatment when all antibodies from a passive treatment would have cleared from circulation. Alternatively, one could challenge the recipient with attenuated rabies to see whether a secondary response occurred (this treatment may be precluded by the ethical ramifications).

Pattern recognition

The ability of a receptor or ligand to interact with a class of similar molecules, such as mannose-containing oligosaccharides. Innate immunity. The ability to recognize a given class of molecules.

plasma cells

The antibody-secreting effector cell of the B lineage.

clonal selection

The antigen-mediated activation and proliferation of members of a clone of B cells that have receptors for the antigen (or for complexes of MHC and peptides derived from the antigen, in the case of T cells.

memory response

The attribute of the immune system mediated by memory cells whereby a second encounter with an antigen induces a heightened state of immune reactivity.

hematopoietic stem cell (HSC)

The cell type from which all lineages of blood cells arise

plasma

The cell-free, fluid portion of blood, which contains all the clotting factors.

hematopoiesis

The formation and differentiation of blood cells.

Infants immediately after birth are often at risk for infection with group B streptococcus. A vaccine is proposed for administration to women of childbearing years. How can immunizing the mother help the babies?

The immunized mothers would confer immunity upon their offspring because the anti-streptococcal antibodies cross the placental barrier and are present in the babies at birth. In addition, the colostrums and milk from the mother would contain antibodies to protect the nursing infant from infection.

medulla

The innermost of central region of an organ

thoracic duct

The largest of the lymphatic vessels. It returns lymph to the circulation by emptying into the left subclavian vein near the heart.

bone marrow

The living tissue found within the hard exterior of bone.

Pathogenesis

The means of attacking the host; the manner of development of a disease.

cortex

The outer or peripheral layer of an organ.

antigenic specificity

The property of mature B and T lymphocytes that enables them to respond to specific foreign antigens entering the body. Antigen specificity requires mature B and T cells that have been previously exposed to the antigen and, therefore, are able to recognize it again and respond by neutralizing or destroying it. The exact process by which B lymphocytes become capable of recognizing and responding to antigens is unknown. Development of antigen specificity by T cells requires macrophage processing of the antigen for recognition.

Name 3 features of a secondary immune response that distinguish it from a primary immune response.

The secondary immune response involves an amplified population of memory cells. The response is more rapid and achieves higher levels than the primary response.

antigenically committed

The state of a mature B cell displaying surface antibody specific for a single immunogen.

The T cell is said to be class I restricted. What does this mean?

They can recognize only antigen that is associated with class I MHC molecules.

lymphatic vessels

Thinly walled vessels through which the fluid and cells of the lymphatic system move through the lymph nodes and ultimately into the thoracic duct, where it joins the bloodstream.

Variolation

Variolation or inoculation was the method first used to immunize an individual against smallpox (Variola) with material taken from a patient or a recently variolated individual in the hope that a mild, but protective infection would result. The dried crusts from smallpox pustules were either inhaled into the nostrils or inserted into small cuts into the skin.

lysozyme

a crystalline, basic protein present in saliva, tears, egg white, and many animal fluids, which functions as an antibacterial enzyme.

Toll-like receptors (TLRs)

a family of pattern-recognition receptors in mammals that can discriminate between chemically diverse classes of microbial products, including bacterial cell-wall components; can elicit pathogen-specific innate cellular immune responses.

lymphocyte

a form of small leukocyte (white blood cell) with a single round nucleus, occurring especially in the lymphatic system. Cell responsible for both cellular and humoral immunity.

Interferon

a protein released by animal cells, usually in response to the entry of a virus, that has the property of inhibiting virus replication; interferon comprises a group of proteins produced by virus infected cells. Among the many functions of interferons is the ability to bind to nearby cells and induce a generalized antiviral state.

platelets

a small colorless disk-shaped cell fragment without a nucleus, found in large numbers in blood and involved in clotting.

Vaccine

a substance used to stimulate the production of antibodies and provide immunity against one or several diseases, prepared from the causative agent of a disease, its products, or a synthetic substitute, treated to act as an antigen without inducing the disease. From the Latin vacca, meaning "cow", in honor of Jenner's work with cowpox inoculation.

phagocytes

a type of cell within the body capable of engulfing and absorbing bacteria and other small cells and particles.

Math the cell type with the receptor found on that cell. Cell Type Receptor a. Antigen presenting cell. 1. CD8+ b. B cell 2. MHC c. Helper T cell 3. BCR d. Cytotoxic T cell 4. CD4+

a) 2 b) 3 c) 4 d) 1

Fill in the blanks of the following statements with the most appropriate terms: a. _____________, _____________, and _____________ all function as antigen-presenting cells. b. Antigen-presenting cells deliver a _____________ signal to _____________ cells. c. Only antigen-presenting cells express lass _____________ molecules, whereas nearly all cells express class _____________ MHC molecules. d. The scientific term that refers to all white blood cells in general is _____________. e. The _____________ arm of the immune system is so called because antibodies are generated in response to specific pathogens. Prior exposure to a pathogen is required for this part of the immune system to develop. f. T cells must have coreceptors so they can efficiently bind to MHC molecules. The coreceptor for recognition of class I MHC is _____________ and the coreceptor for recognition of class II is called _____________. g. The part of the antigen bound by an antibody is known as the _____________.

a) Macrophages, B cells, dendritic cells. b) Co-stimulatory; TH cells. c) II ; I d) Leukocyte e) Adaptive f) CD8, CD4 g) Epitope

Which of the following statements about how B and T cells recognize antigen are true? a. B cells only recognize antigen presented by class I or class II MHC molecules. b. Both cell types can recognize antigen in solution (without cells). c. Both cell types recognize extracellular matrix-bound antigens. d. T cells only recognize antigen presented by class I or class II MHC molecules.

a) false b) false c) false d) true

For each of the following statements, indicate whether the statement is true or false. If you think the statement is false, explain why. a. Booster shots are required because repeated exposure to an antigen builds a stronger immune response. b. The gene for the T cell receptor must be cut and spliced together, deleting entire sections, before it can be transcribed. c. Our bodies face the greatest onslaught from foreign invaders through our mucus membranes. d. Increased production of antibody in the immune system is driven by the presence of antigen. e. Antigens is bound directly by T cells. f. Peptides are added to the binding of cleft of class MHC I molecules in the cytosol. g. In order for B cells to mature into plasma cells they need "help" from T cells.

a) true b) true c) true d) true e) false; antigen must be presented to T cells in the context of MHC molecules f) false: peptides are added to the binding cleft of MHC class I in a vesicle g) true

Indicate to which branch(es) of the immune system the following statements apply, using H for the humoral branch and CM for the cell-mediated branch. Some statements may apply to both branches. a. Involves class I MHC molecules b. Responds to viral infection c. Involves T helper cells d. Involves processed antigen e. Responds following an organ transplant f. Involves T cytotoxic cells g. Involves B cells h. Involves T cells i. Responds to extracellular bacterial infection j. Involves secreted antibody k. Kills virus-infected self cells

a. CM b. H and CM c. H and CM d. H and CM e. CM f. CM g. H h. CM i. H j. H k. CM

Dysfunctions of the immune system include common maladies such as

allergies and asthma as well as immunodeficiency and autoimmunity

Serum

an amber-colored, non cellular, protein-rich liquid that separates out when blood coagulates.

antigen

an antigen is a molecule capable of inducing an immune response on the part of the host organism, though sometimes antigens can be part of the host itself. In other words, an antigen is any substance that causes an immune system to produce antibodies against it. The general term for a substance that binds with a specific antibody.

T-cell epitopes are generated by

antigen processing, which fragments protein into small peptides that combine with class I or class II MHC molecules to form peptide-MHC complexes that are displayed on the surface of cells. T-cell activation requires the formation of a ternary complex between a T cell's TCR and peptide-MHC on antigen-presenting or altered self cells.

Antibodies recognize and interact directly with

antigen. T-cell receptors recognize only antigen combined with major histocompatibility complex (MHC) molecules.

Innate immunity constitutes a first line of defense, which includes:

barriers, phagocytic cells, and molecules that recognize certain types of pathogens

Immature forms of the dendritic cells have the capacity to

capture antigen in one location, undergo maturation and migrate to another location, where they present antigen to TH cells. Dendritic cells are the major population of antigen presenting cells.

antigen-presenting cells (APCs)

cells that process protein antigens into peptides and present them on their surface in a form that can be recognized by lymphocytes. APCs include Langerhans cells, dendritic cells, macrophages, B cells, and, in humans, activated T cells.

Innate and adaptive immunity operate

cooperatively; activation of the innate immune response produces signals that stimulate a subsequent adaptive immune response

naive

denoting mature T and B cells that have not encountered antigen; synonymous with unprimed and virgin.

Primary lymphoid organs are the sites where lymphocytes

develop and mature. T cells arise in the bone marrow and develop in the thymus; in humans and mice, B cells arise and develop in bone marrow.

Many of the body's cells, tissues, and organs arise from

different stem cell populations. Leukocytes develop from a pluripotent hematopoietic stem cell during a highly regulated process called hematopoiesis.

Agglutinate

firmly stick or be stuck together to form a mass.

Immunogenicity is determined by many factors including

foreignness, molecular size, chemical composition, complexity, dose, susceptibility to antigen processing and presentation, the genotype of the recipient animal (in particular, its MHC genes), route of administration, and adjuvants.

All immunogens are antigens but not all antigens are

immunogens

complement

includes a group of serum proteins that circulate in an inactive state. A variety of specific and non specific immunologic mechanisms can convert inactive forms of complement proteins into an active state with the ability to damage the membranes of pathogenic organisms, either destroying the pathogens or facilitating their clearance. Complement occupies a position that truly straddles the innate and adaptive immune systems, in that certain components may directly deal with pathogens, whereas others require prior binding of antibodies to activate its effector system.

Vertebrates have 2 types of immunity:

innate and adaptive

Secondary lymphoid organs provide sites where

lymphocytes encounter antigen, become activated, and undergo clonal expansion and differentiation into effector cells.

The high degree of specificity in adaptive immunity resides in

molecules (antibodies and T-cell receptors) that recognize and bind specific antigens

The innate immune system uses

pattern-recognition receptors to recognize and respond to broad structural motifs that are highly conserved within microbial species but are generally absent from the host.

Apoptosis, a type of

programmed cell death, is a key factor in regulating the levels of hematopoietic and other cell populations.

Haptens are

small molecules that can bind to antibodies but cannot by themselves induce an immune response. However, the conjugate formed by coupling a hapten to a large carrier protein is immunogenic and elicits production of anti-hapten antibodies when injected into an animal. Such injections also produce anti-carrier and antihapten/ carrier antibodies as well.

The 2 major subpopulations of T lymphocytes are

the CD4+ T helper (TH) cells and CD8+ T cytotoxic (Tc) cells, which give rise to cytotoxic T cells (CTLs)

In the body, the formation of hapten-carrier conjugates is

the basis of allergic responses to drugs such as penicillin.

The humoral (antibody) and cell mediated responses of the immune system result from

the coordinated activities of many types of cells, organs, and tissues found throughout the body.

active immunity

the immunity that results from the production of antibodies by the immune system in response to the presence of an antigen.

Vertebrate orders differ greatly in

the kinds of lymphoid organs, tissues and cells they possess. They most primitive, the jawless fish, lack B and T cells and can not mount adaptive immune responses; jawed vertebrates have T and B cells, have adaptive immunity, and display and increasing variety of lymphoid tissues.

Macrophages and neutrophils are specialized for

the phagocytosis and degradation of antigens. Macrophages also have the capacity to present antigens to T cells.

epitope

the portion of an antigen that is recognized and bound by an antibody or TCR-MHC combination; also called antigenic determinant.

passive immunity

the short-term immunity that results from the introduction of antibodies from another person or animal.

immunity

the state of being immune from or insusceptible to a particular disease or the like. 2. the condition that permits either natural or acquired resistance to disease. 3. the ability of a cell to react immunologically in the presence of an antigen.

Immunity is

the state of protection against foreign organisms or substances (antigens)