BIO - TERMS - ANTIGEN Flashcards
(210 cards)
1
Q
ABO blood group system
A
The classification of red blood cells based on the presence or absence of A and B carbohydrate antigens.
2
Q
accessory effector cells
A
Cells that aid in an adaptive immune response but are not involved in specific antigen recognition. They include phagocytes, neutrophils, mast cells, and NK cells.
3
Q
acellular pertussis vaccines
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A formulation of pertussis used for vaccination containing chemically inactivated antigens, including pertussis toxoid.
4
Q
activated macrophage
A
A macrophage that has increased phagocytic ability and other functions after exposure to mediators released by T cells after stimulation by antigens.
5
Q
afferent lymphatic vessels
A
Vessels of the lymphatic system that drain extracellular fluid from the tissues and carry antigen, macrophages, and dendritic cells from sites of infection to lymph nodes or other peripheral lymphoid organs.
6
Q
agnathan paired receptors resembling Ag receptors (APARs)
A
Multigene family of genes containing immunoglobulin domains present in hagfish and lamprey, that possibly represent ancestral predecessors of mammalian antigen receptors.
7
Q
allelic exclusion
A
In a heterozygous individual, the expression of only one of the two alternative alleles of a particular gene. In immunology, the term describes the restricted expression of the individual chains of the antigen receptor genes, such that each individual lymphocyte produces immunoglobulin or T-cell receptors of a single antigen specificity.
8
Q
allergic asthma
A
An allergic reaction to inhaled antigen, which causes constriction of the bronchi, increased production of airway mucus, and difficulty in breathing.
9
Q
allergic reaction
A
A specific response to an innocuous environmental antigen, or allergen, that is caused by sensitized B or T cells. Allergic reactions can be caused by various mechanisms, but the most common is the binding of allergen to IgE bound to mast cells, which causes the cells to release histamine and other biologically active molecules that cause the signs and symptoms of asthma, hay fever, and other common allergic responses.
10
Q
allergy
A
The state in which a symptomatic immune reaction is made to a normally innocuous environmental antigen. It involves the interaction between the antigen and antibody or primed T cells produced by earlier exposure to the same antigen.
11
Q
alloantibodies
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Antibodies produced against antigens from a genetically nonidentical member of the same species.
12
Q
alloantigens
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Antigens from another genetically nonidentical member of the same species.
13
Q
alum
A
Inorganic aluminum salts (for example aluminum phosphate and aluminum hydroxide); they act as adjuvants when mixed with antigens and are one of the few adjuvants permitted for use in humans.
14
Q
anchor residues
A
Specific amino acid residues in antigenic peptides that determine peptide binding specificity to MHC class I molecules. Anchor residues for MHC class II molecules exist but are less obvious than for MHC class I.
15
Q
anergy
A
A state of nonresponsiveness to antigen. People are said to be anergic when they cannot mount delayed-type hypersensitivity reactions to a test antigen, whereas T cells and B cells are said to be anergic when they cannot respond to their specific antigen under optimal conditions of stimulation.
16
Q
antibody response
A
Adaptive immune response in which B cells are activated to secrete antibodies that circulate in the bloodstream or enter other body fluids, where they can bind specifically to the foreign antigen that stimulated their production.
17
Q
antigen presentation
A
The display of antigen on the surface of a cell in the form of peptide fragments bound to MHC molecules. T cells recognize antigen when it is presented in this way.
18
Q
antigen processing
A
The intracellular degradation of foreign proteins into peptides that can bind to MHC molecules for presentation to T cells. All protein antigens must be processed into peptides before they can be presented by MHC molecules.
19
Q
antigen receptor
A
The cell-surface receptor by which lymphocytes recognize antigen. Each individual lymphocyte bears receptors of a single antigen specificity.
20
Q
AP-1
A
A heterodimeric transcription factor formed as one of the outcomes of intracellular signaling via the antigen receptors of lymphocytes and the TLRs of cells of innate immunity. Most often, contains one Fos-family member and one Jun-family member. AP-1 mainly activates the expression of genes for cytokines and chemokines.
21
Q
autoantibodies
A
Antibodies specific for self antigens.
22
Q
autoantigens
A
A self antigen to which the immune system makes a response.
23
Q
autoimmune hemolytic anemia
A
A pathological condition with low levels of red blood cells (anemia), which is caused by autoantibodies that bind red blood cell surface antigens and target the red blood cell for destruction.
24
Q
autoimmune polyendocrinopathy–candidiasis–ectodermal dystrophy (APECED)
A
A disease characterized by a loss of tolerance to self antigens, caused by a breakdown of negative selection in the thymus. It is due to defects in the gene AIRE, which encodes a transcriptional regulatory protein that enables many self antigens to be expressed by thymic medullary epithelial cells. Also called autoimmune polyglandular syndrome type I.
25
autoimmunity
Adaptive immunity specific for self antigens.
26
B-1 B cells
A class of atypical, self-renewing B cells (also known as CD5 B cells) found mainly in the peritoneal and pleural cavities in adults and considered part of the innate rather than the adaptive immune system. They have a much less diverse antigen-receptor repertoire than conventional B cells and are the major source of natural antibody.
27
B-cell co-receptor complex
A transmembrane signaling receptor on the B-cell surface composed of the proteins CD19, CD81, and CD21 (complement receptor 2), which binds complement fragments on bacterial antigens also bound by the B-cell receptor. Co-ligation of this complex with the B-cell receptor increases responsiveness to antigen about 100-fold.
28
B7 molecules, B7.1 and B7.2
Cell-surface proteins on specialized antigen-presenting cells such as dendritic cells, which are the major costimulatory molecules for T cells. B7.1 (CD80) and B7.2 (CD86) are closely related members of the immunoglobulin superfamily and both bind to the CD28 and CTLA-4 proteins on T cells.
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BDCA-2 (blood dendritic cell antigen 2)
A C-type lectin expressed selectively as a receptor on the surface of human plasmacytoid dendritic cells.
30
cancer-testis antigens
Proteins expressed by cancer cells that are normally expressed only in male germ cells in the testis.
31
cathepsins
A family of proteases using cysteine at their active site that frequently function in processing antigens taken into the vesicular pathway.
32
caveolins
Family of unusual integral membrane proteins that are the major structural proteins in caveolae, CD4 Co-receptor protein on helper T cells and regulatory T cells that binds to a nonvariable part of class II MHC proteins (on antigen-presenting cells) outside the peptide-binding groove.
33
CD (cluster of differentiation)
Number assigned to an epitope on a single antigen, for example, CD4 protein, which is found on T helper cells.
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CD1
Small family of MHC class I-like proteins that are not encoded in the MHC and can present glycolipid antigens to CD4 T cells.
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CD103
Integrin αE:β7, a cell-surface marker on a subset of dendritic cells in the gastrointestinal tract that are involved in inducing tolerance to antigens from food and the commensal microbiota.
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CD28
An activating receptor on T cells that binds to the B7 co-stimulatory molecules present on specialized antigen-presenting cells such as dendritic cells. CD28 is the major co-stimulatory receptor on naive T cells.
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CD30, CD30 ligand
CD30 on B cells and CD30 ligand (CD30L) on helper T cells are co-stimulatory molecules involved in stimulating the proliferation of antigen-activated naive B cells.
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CD4
The co-receptor for T-cell receptors that recognize peptide antigens bound to MHC class II molecules. It binds to the lateral face of the MHC molecule.
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CD40, CD40 ligand
CD40 on B cells and CD40 ligand (CD40L, CD154) on activated helper T cells are co-stimulatory molecules whose interaction is required for the proliferation and class switching of antigen activated naive B cells. CD40 is also expressed by dendritic cells, and here the CD40–CD40L interaction provides co-stimulatory signals to naive T cells.
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CD45
A transmembrane tyrosine phosphatase found on all leukocytes. It is expressed in different isoforms on different cell types, including the different subtypes of T cells. Also called leukocyte common antigen, it is a generic marker for hematopoietically derived cells, with the exception of erythrocytes.
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CD69
A cell-surface protein that is rapidly expressed by antigen-activated T cells. It acts to down-modulate the expression of the sphingosine 1 phosphate receptor 1 (S1PR1), thereby retaining activated T cells within T-cell zones of secondary lymphoid tissues as they divide and differentiate into effector T cells.
42
CD86 (B7-2)
A transmembrane protein of the immunoglobulin superfamily that is expressed on antigen-presenting cells and binds to CD28 expressed by T cells.
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cellular hypersensitivity reactions
A hypersensitivity reaction mediated largely by antigen-specific T lymphocytes.
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cellular immunity (cell-mediated immunity)
An immune response that involves T cells binding to antigens presented on antigen-presenting cells; T cells then differentiate into several types of effector T cells.
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central tolerance
Immunological tolerance to self antigens that is established while lymphocytes are developing in central lymphoid organs. Cf. peripheral tolerance.
46
chimeric antigen receptor (CAR)
Engineered fusion proteins composed of extracellular antigen-specific receptors (e.g., single-chain antibody) and intracellular signaling domains that activate and co-stimulate, expressed in T cells for use in cancer immunotherapy.
47
class II MHC protein
One of two classes of major histocompatibility complex (MHC) protein. Found on the surface of various antigen-presenting cells, where it presents peptides to helper and regulatory T cells.
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classical MHC class I genes
MHC class I genes whose proteins function by presenting peptide antigens for recognition by T cells. Cf. nonclassical MHC class Ib.
49
clonal expansion
The proliferation of antigen-specific lymphocytes in response to antigenic stimulation that precedes their differentiation into effector cells. It is an essential step in adaptive immunity, allowing rare antigen-specific cells to increase in number so that they can effectively combat the pathogen that elicited the response.
50
clonal selection theory
The central paradigm of adaptive immunity. It states that adaptive immune responses derive from individual antigenspecific lymphocytes that are self-tolerant. These specific lymphocytes proliferate in response to antigen and differentiate into antigen-specific effector cells that eliminate the eliciting pathogen, and into memory cells to sustain immunity. The theory was formulated by Macfarlane Burnet and in earlier forms by Niels Jerne and David Talmage.
51
clonotypic
Describes a feature unique to members of a clone. For example, the distribution of antigen receptors in the lymphocyte population is said to be clonotypic, as the cells of a given clone all have identical antigen receptors.
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co-stimulatory molecules
Cell-surface proteins on antigen-presenting cells that deliver co-stimulatory signals to naive T cells. Examples are the B7 molecules on dendritic cells, which are ligands for CD28 on naive T cells.
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co-stimulatory receptors
Cell-surface receptors on naive lymphocytes through which the cells receive signals additional to those received through the antigen receptor, and which are necessary for the full activation of the lymphocyte. Examples are CD30 and CD40 on B cells, and CD27 and CD28 on T cells.
54
co-stimulatory signal
In immunology: a secreted or membrane-bound signal protein that helps activate an antigenresponding B cell or T cell.
55
combinatorial diversity
The diversity among antigen receptors generated by combining separate units of genetic information, comprising two types. First, receptor gene segments are joined in many different combinations to generate diverse receptor chains; second, two different receptor chains (heavy and light in immunoglobulins; α and β, or γ and δ, in T-cell receptors) are combined to make the antigen-recognition site.
56
complement fixation
The process in which complement combines with an antigen–antibody complex.
57
complement receptors (CRs)
Cell-surface proteins of various types that recognize and bind complement proteins that have become bound to an antigen such as a pathogen. Complement receptors on phagocytes enable them to identify and bind pathogens coated with complement proteins, and to ingest and destroy them. See CR1, CR2, CR3, CR4, CRIg, and the C1 complex.
58
complementarity-determining regions (CDRs)
Parts of the V domains of immunoglobulins and T-cell receptors that determine their antigen specificity and make contact with the specific ligand. The CDRs are the most variable part of antigen receptor, and contribute to the diversity of these proteins. There are three such regions (CDR1, CDR2, and CDR3) in each V domain.
59
conformational epitopes, discontinuous epitopes
Antigenic structure (epitope) on a protein antigen that is formed from several separate regions in the sequence of the protein brought together by protein folding. Antibodies that bind conformational epitopes bind only native folded proteins.
60
conjugated vaccine
A vaccine consisting of the desired antigen and other proteins.
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continuous epitope, linear epitope
Antigenic structure (epitope) in a protein that is formed by a single small region of amino acid sequence. Antibodies that bind continuous epitopes can bind to the denatured protein. The epitopes detected by T cells are continuous. Also called a linear epitope.
62
conventional (or classical) dendritic cells (cDCs)
The lineage of dendritic cells that mainly participates in antigen presentation to, and activation of, naive T cells. Cf. plasmacytoid dendritic cells.
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CR2 (CD21)
Complement receptor that is part of the B-cell co-receptor complex. It binds to antigens coated with breakdown products of C3b, especially C3dg, and, by cross-linking the B-cell receptor, enhances sensitivity to antigen at least 100-fold. It is also the receptor used by the Epstein–Barr virus to infect B cells.
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CRAC channel
Channels in the lymphocyte plasma membrane that open to let calcium flow into the cell during the response of the cell to antigen. Channel opening is induced by release of calcium from the endoplasmic reticulum.
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cross-priming
Activation of CD8 T cells by dendritic cells in which the antigenic peptide presented by MHC class I molecules is derived from an exogenous protein (i.e., by cross-presentation), rather than produced within the dendritic cells directly. Cf. direct presentation.
66
cryptic epitopes
Any epitope that cannot be recognized by a lymphocyte receptor until the antigen has been broken down and processed.
67
CTL (cytotoxic T lymphocyte)
An activated CD8+ T cell; kills cells presenting endogenous antigens.
68
Cutaneous immune system
The lymphocytes and scavenger antigen-presenting cells (Langerhans cells) that comprise the skinassociated lymphoid tissue. (Chapter 4)
69
cutaneous lymphocyte antigen (CLA)
A cell-surface molecule that is involved in lymphocyte homing to the skin in humans.
70
cyclophosphamide
A DNA alkylating agent that is used as an immunosuppressive drug. It acts by killing rapidly dividing cells, including lymphocytes proliferating in response to antigen.
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Delayed-type hypersensitivity
A reaction caused by CD4 T cells that recognizes antigens in the skin; the reaction typically occurs hours to days aft er antigen is injected, hence its name; it is partially responsible for characteristic local responses to virus infections, such as rashes. (Chapter 4)
72
delayed-type hypersensitivity reactions
A form of cell-mediated immunity elicited by antigen in the skin stimulating sensitized Th1 CD4 lymphocytes and CD8 lymphocytes. It is called delayed-type hypersensitivity because the reaction appears hours to days after antigen is injected. Referred to as type IV hypersensitivity in the historic Gell and Coombs classification.
73
differentiation antigens
Referring to a category of genes with restricted expression patterns that can be targeted as antigens by immunotherapies in treatment of cancers.
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direct agglutination test
The use of known antibodies to identify an unknown cell-bound antigen.
75
direct allorecognition
Host recognition of a grafted tissue that involves donor antigen-presenting cells leaving the graft, migrating via the lymph to regional lymph nodes, and activating host T cells bearing the corresponding T-cell receptors.
76
direct fluorescent-antibody (DFA) test
A fluorescent-antibody test to detect the presence of an antigen.
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direct presentation
The process by which proteins produced within a given cell give rise to peptides presented by MHC class I molecules. This may refer to antigen-presenting cells, such as dendritic cells, or to nonimmune cells that will become the targets of CTLs.
78
DNA vaccination
Vaccination by introduction into skin and muscle of DNA encoding the desired antigen; the expressed protein can then elicit antibody and T-cell responses.
79
draining lymph nodes
A lymph node downstream of a site of infection that receives antigens and microbes from the site via the lymphatic system. Draining lymph nodes often enlarge enormously during an immune response and can be palpated; they were originally called swollen glands.
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effector lymphocytes
The cells that differentiate from naive lymphocytes after initial activation by antigen and can then mediate the removal of pathogens from the body without further differentiation. They are distinct from memory lymphocytes, which must undergo further differentiation to become effector lymphocytes.
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endogenous
(1) Infection caused by an opportunistic pathogen from an individual’s own normal microbiota. (2) Surface antigens on human cells produced as a result of infection.
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Endogenous antigen presentation
Th e cellular process by which viral proteins are degraded inside the infected cell, and the resulting peptides are loaded onto major histocompatibility complex class I molecules that move to the cell surface. (Chapter 4)
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epitope spreading
Increase in diversity of responses to autoantigens as the response persists, as a result of responses being made to epitopes other than the original one.
84
equilibrium phase
Stage of anti-tumor immune response when immunoediting allows the immune response to continuously shape the antigenic character of cancer cells.
85
escape mutants
Mutants of pathogens that are changed in such a way that they can evade the immune response against the original pathogen. escape phase Final stage of anti-tumor immune response when immunoediting has removed the expression of antigenic targets such that the cancer cells are no loner detected by the immune system.
86
Exogenous antigen presentation
Th e cellular process in which viral proteins are engulfed from the outside of the cell, degraded, and the resulting peptides loaded onto major histocompatibility complex class II molecules that then move to the cell surface for presentation to T cells. (Chapter 4)
87
experimental autoimmune encephalomyelitis (EAE)
An inflammatory disease of the central nervous system that develops after mice are immunized with neural antigens in a strong adjuvant.
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farmer’s lung
A hypersensitivity disease caused by the interaction of IgG antibodies with large amounts of an inhaled antigen in the alveolar wall of the lung, causing alveolar wall inflammation and compromising respiratory gas exchange.
89
FcεRI
The high affinity receptor for the Fc region of IgE. Expressed primarily on the surface of mast cells and basophils. When multivalent antigen interacts with IgE that is bound to FcεRI and cross-links nearby receptors, it causes activation of the receptor-bearing cell.
90
follicle-associated epithelium
Specialized epithelium separating the lymphoid tissues of the gut wall from the intestinal lumen. As well as enterocytes it contains microfold cells, through which antigens enter the lymphoid organs from the gut.
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follicular dendritic cell (FDC)
A cell type of uncertain origin in B-cell follicles of peripheral lymphoid organs that captures antigen:antibody complexes using non-internalized Fc receptors and presents them to B cells for internalization and processing during the germinal center reaction.
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Freund’s complete adjuvant
Emulsion of oil and water containing killed mycobacteria used to enhance immune responses to experimental antigens.
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gene segments
Sets of short DNA sequences at the immunoglobulin and T-cell receptor loci that encode different regions of the variable domains of antigen receptors. Gene segments of each type are joined together by somatic recombination to form a complete variable-domain exon. There are three types of gene segments: V gene segments encode the first 95 amino acids, D gene segments (in heavy-chain and TCRα chain loci only) encode about 5 amino acids, and J gene segments encode the last 10–15 amino acids of the variable domain. There are multiple copies of each type of gene segment in the germline DNA, but only one of each type is joined together to form the variable domain.
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graft-versus-leukemia effect
A beneficial side-effect of bone marrow grafts given to treat leukemia, in which mature T cells in the graft recognize minor histocompatibility antigens or tumor-specific antigens on the recipient’s leukemic cells and attack them.
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H antigen
Flagella antigens of enterics, identified by serological testing.
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HA (hemagglutinin) spike
Antigenic projections from the outer lipid bilayer of Influenzavirus.
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heavy-chain-only IgGs (hcIgGs)
Antibodies produced by some camelid species composed of heavy-chain dimers without an associated light chain that retain antigen binding capacity.
98
hemagglutinin (HA)
Substances that can cause hemagglutination, such as human antibodies that recognize the ABO blood group antigens on red blood cells, or the influenza virus hemagglutinin, a glycoprotein that functions in viral fusion with endosome membranes.
99
Heterologous T cell immunity
A secondary T cell response to antigen that is related but not identical to the immunodominant antigens that elicited the primary T cell response. (Chapter 5)
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histocompatibility antigen
An antigen on the surface of human cells.
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human leukocyte antigen (HLA) complex
Human cell surface antigens. See also major histocompatibility complex.
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ICAMs ICAM-1, ICAM-2, ICAM-3.
Cell-adhesion molecules of the immunoglobulin superfamily that bind to the leukocyte integrin CD11a:CD18 (LFA-1). They are crucial in the binding of lymphocytes and other leukocytes to antigen-presenting cells and endothelial cells.
103
ILCs (innate lymphoid cells)
These are a class of innate immune cells having overlapping characteristics with T cells but lacking an antigen receptor. They arise in several groups, ILC1, ILC2, ILC3, and NK cells, which exhibit properties roughly similar to TH1, TH2, TH17, and CD8 T cells.
104
immediate hypersensitivity reactions
Allergic reactions that occur within seconds to minutes of encounter with antigen, caused largely by activation of mast cells or basophils.
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Immune memory
A property provided by specialized B and T lymphocytes (memory B and T cells) that respond rapidly upon reexposure to an antigen. (Chapter 8)
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immune response
The capacity of a vertebrate to generate antibodies to an antigen, a macromolecule foreign to the organism.
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immunocompetence
(im′ū-nō- kom′pĕ-tens) Ability of immune cells to recognize and bind to an antigen.
108
immunoglobulin new antigen receptor (IgNAR)
A form of heavy-chainonly Ig molecule made by shark species.
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immunoglobulin repertoire
The variety of antigen-specific immunoglobulins (antibodies and B-cell receptors) present in an individual. Also known as the antibody repertoire.
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immunological self-tolerance
The lack of response of the adaptive immune system to an antigen. Tolerance to self molecules is crucial to avoid autoimmune diseases.
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immunological ignorance
A form of self-tolerance in which reactive lymphocytes and their target antigen are both detectable within an individual, yet no autoimmune attack occurs.
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immunologically privileged sites
Certain sites in the body, such as the brain, that do not mount an immune response against tissue allografts. Immunological privilege can be due both to physical barriers to cell and antigen migration and to the presence of immunosuppressive cytokines.
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immunoreceptor tyrosine-based activation motif (ITAM)
Sequence motifs in the signaling chains of receptors, such as antigen receptors on lymphocytes, that are the site of tyrosine phosphorylation after receptor activation, leading to recruitment of other signaling proteins.
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indirect (passive) agglutination test
An agglutination test using soluble antigens attached to latex or other small particles.
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indirect allorecognition
Recognition of a grafted tissue that involves the uptake of allogeneic proteins by the recipient’s antigen-presenting cells and their presentation to T cells by self MHC molecules.
116
invariant chain (Ii, CD74)
A polypeptide that binds in the peptidebinding cleft of newly synthesized MHC class II proteins in the endoplasmic reticulum and blocks other peptides from binding there. It is degraded in the endosome, allowing for loading of antigenic peptides there.
117
invariant NKT cells (iNKT cells)
A type of innate-like lymphocyte that carries a T-cell receptor with an invariant α chain and a β chain of limited diversity that recognizes glycolipid antigens presented by CD1 MHC class Ib molecules. This cell type also carries the surface marker NK1.1, which is usually associated with NK cells.
118
Ir (immune response) genes
An archaic term for genetic polymorphisms controlling the intensity of the immune response to a particular antigen, now known to result from allelic differences in MHC molecules, especially MHC class II molecules, that influence binding of particular peptides.
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junctional diversification
The random loss and gain of nucleotides at joining sites during V(D)J recombination that occurs during B and T cell development when the cells are assembling the gene segments that encode their antigen receptors. It enormously increases the diversity of V-region coding sequences.
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junctional diversity
The variability in sequence present in antigenspecific receptors that is created during the process of joining V, D, and J gene segments and which is due to imprecise joining and insertion of nontemplated nucleotides at the joins between gene segments.
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kinase suppressor of Ras
A scaffold protein in the Raf–MEK1–Erk MAPkinase cascade that binds to all three members following antigen receptor signaling to facilitate their interactions and to accelerate the signaling cascade.
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late-phase reaction
Allergic reactions that occurs several hours after initial encounter with an antigen. Thought to be manifestations of recruitment of multiple leukocyte subsets to the site of allergen exposure.
123
Lck
An Src-family tyrosine kinase that associates with the cytoplasmic tails of CD4 and CD8 and phosphorylates the cytoplasmic tails of the T-cell receptor signaling chains, thus helping to activate signaling from the T-cell receptor complex once antigen has bound.
124
leukocyte functional antigens (LFAs)
Cell-adhesion molecules on leukocytes that were initially defined using monoclonal antibodies. LFA‑1 is a β2 integrin; LFA-2 (now usually called CD2) is a member of the immunoglobulin superfamily, as is LFA-3 (now called CD58). LFA‑1 is particularly important in T-cell adhesion to endothelial cells and antigenpresenting cells.
125
licensing
The activation of a dendritic cell so that it is able to present antigen to naive T cells and activate them.
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linked recognition
The rule that for a helper T cell to be able to activate a B cell, the epitopes recognized by the B cell and the helper T cell have to be derived from the same antigen (that is, they must originally have been physically linked).
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lymphocyte receptor repertoire
All the highly variable antigen receptors carried by B and T lymphocytes.
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lymphoid organ
An organ containing large numbers of lymphocytes. Lymphocytes are produced in primary lymphoid organs and respond to antigen in peripheral lymphoid organs. (Figure 24–12)
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mature B cell
B cell that expresses IgM and IgD on its surface and has gained the ability to respond to antigen.
130
melanoma-associated antigens (MAGE)
Heterogeneous group of proteins of diverse or unknown functions characterized by restricted expression limited to tumors (i.e., melanoma) or testis germ cells.
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membrane immunoglobulin (mIg)
Transmembrane immunoglobulin present on B cells; it is the B-cell receptor for antigen.
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memory response
A rapid rise in antibody titer following exposure to an antigen after the primary response to that antigen; also called anamestic response or secondary response.
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MHC class I molecules
Polymorphic cell-surface proteins encoded in the MHC locus and expressed on most cells. They present antigenic peptides generated in the cytosol to CD8 T cells, and also bind the co-receptor CD8.
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MHC class II compartment (MIIC)
The cellular vesicles in which MHC class II molecules accumulate, encounter HLA-DM, and bind antigenic peptides, before migrating to the surface of the cell.
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MHC class II molecules
Polymorphic cell-surface proteins encoded in the MHC locus are expressed primarily on specialized antigen-presenting cells. They present antigenic peptides derived from internalized extracellular pathogens to CD4 T cells and also bind the co-receptor CD4.
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MHC molecules
Highly polymorphic cell-surface proteins encoded by MHC class I and MHC class II genes involved in presentation of peptide antigens to T cells. They are also known as histocompatibility antigens.
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microclusters
Assemblies of small numbers of T-cell receptors that may be involved in the initiation of T-cell receptor activation by antigen in naive T cells.
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minor histocompatibility antigens
Peptides of polymorphic cellular proteins bound to MHC molecules that can lead to graft rejection when they are recognized by T cells.
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minor lymphocyte stimulating (Mls) antigens
An old term referring to non-MHC antigens responsible for unusually strong T cell responses to cells from different strains of mice, now known to be superantigens encoded by endogenous retroviruses.
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mucosal immune system
The immune system that protects internal mucosal surfaces (such as the linings of the gut, respiratory tract, and urogenital tracts), which are the site of entry for virtually all pathogens and other antigens. See also mucosa-associated lymphoid tissue.
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mucosal tolerance
The suppression of specific systemic immune responses to an antigen by the previous administration of the same antigen by a mucosal route.
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mycophenolate
An inhibitor of the synthesis of guanosine monophosphate that acts as a cytotoxic immunosuppressive drug. It acts by killing rapidly dividing cells, including lymphocytes proliferating in response to antigen.
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NA (neuraminidase) spikes
Antigenic projections from the outer lipid bilayer of Influenzavirus.
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NAIP5
An NLR protein that, together with NLRC4, recognizes intracellular flagellin to activate an inflammasome pathway in response to infection. naive lymphocytes T cells or B cells that have undergone normal development in the thymus or the bone marrow but have not yet been activated by foreign (or self) antigens.
145
natural antibodies
Antibodies produced by the immune system in the apparent absence of any infection. They have a broad specificity for self and microbial antigens, can react with many pathogens, and can activate complement.
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neoepitopes
Type of tumor rejection antigen created by mutations in protein that can be presented by self-MHC molecules to T cells.
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NFκB
A heterodimeric transcription factor activated by the stimulation of Toll-like receptors and also by antigen receptor signaling composed of p50 and p65 subunits.
148
non-canonical NFκB pathway
A pathway for NFκB activation that is distinct from the one activated by antigen receptor stimulation. This pathway leads to activation of the NFκB-inducing kinase, NIK, which phosphorylates and activates IκB kinase α (IKKα) inducing cleavage of the NFκB precursor protein p100 to form the active p52 subunit.
149
nonclassical MHC class Ib genes
A class of proteins encoded within the MHC that are related to the MHC class I molecules but are not highly polymorphic and present a restricted set of antigens.
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nuclear factor of activated T cells
A family of transcription factors that are activated in response to increased cytoplasmic calcium following antigen receptor signaling in lymphocytes.
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NY-ESO-1
A particular highly immunogenic cancer-testis antigen expressed by many types of human tumors including melanoma.
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O antigen
Polysaccharide antigens in the outer membrane of gramnegative bacteria, identified by serological testing.
153
oral tolerance
The suppression of specific systemic immune responses to an antigen by the prior administration of the same antigen by the oral (enteric) route.
154
PD-1
Programmed death-1, a receptor on T cells that when bound by its ligands, PD-L1 and PD-L2, inhibits signaling from the antigen receptor. PD-1 contains an ITIM motif in its cytoplasmic tail. Target of cancer therapies aimed at stimulating T-cell responses to tumors.
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pentameric IgM
Major form of the IgM antibodies produced by the action of J chain resulting in higher avidity for antigens.
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peptide editing
In the context of antigen processing and presentation, the removal of unstably bound peptides from MHC class II molecules by HLA-DM.
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peptide-binding cleft
The longitudinal cleft in the top surface of an MHC molecule into which the antigenic peptide is bound. Sometimes called the peptide-binding groove.
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physiological inflammation
The state of the normal healthy intestine, whose wall contains large numbers of effector lymphocytes and other cells. It is thought to be the result of continual stimulation by commensal organisms and food antigens.
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polyclonal activation
The activation of lymphocytes by a mitogen regardless of antigen specificity, leading to the activation of clones of lymphocytes of multiple antigen specificities.
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primary Ig repertoire
The billions of IgM and IgD immunoglobulin molecules made by the B cells of an adaptive immune system in the absence of antigen stimulation.
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primary response
Antibody production in response to the first contact with an antigen. See also memory response.
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Professional antigen-presenting cells
Dendritic cells, macrophages, and B cells; defi ned by their ability to take up antigens and present them to naïve T lymphocytes in the groove of an major histocompatibility complex class II molecule. (Chapter 4)
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Proliferating cell nuclear antigen (PCNA)
A clamp protein that holds the DNA template during eukaryotic DNA replication.
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Prostate-specific antigen (PSA)
A marker for prostatic cancer.
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protein kinase C-θ (PKC-θ)
A serine/threonine kinase that is activated by diacylglycerol as part of the signaling pathways from the antigen receptor in lymphocytes.
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Rh factor
An antigen on red blood cells of rhesus monkeys and most humans; possession makes the cells Rh+.
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seasonal allergic rhinoconjunctivitis
IgE-mediated allergic rhinitis and conjunctivitis caused by exposure to specific seasonally occurring antigens, for example grass or weed pollens. Commonly called hay fever.
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Secondary antibody response
Th e antibody response produced aft er a subsequent infection or challenge with the same antigen or virus. (Chapter 4)
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secondary Ig repertoire
Immunoglobulins produced by B cells after antigen- and helper-T-cell-induced somatic hypermutation and class switching. Compared to the primary Ig repertoire, these Igs have a greatly increased diversity of both Ig classes and antigen-binding sites and have increased affinity for antigen.
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secondary immunization
A second or booster injection of an antigen, given some time after the initial immunization. It stimulates a secondary immune response.
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self antigens
The potential antigens on the tissues of an individual, against which an immune response is not usually made except in the case of autoimmunity.
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self-tolerance
The failure to make an immune response against the body’s own antigens.
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sensitized
In allergy, describes an individual who has made an IgE response on initial encounter with an environmental antigen and who manifests IgE-producing memory B cells. Subsequent allergen exposure can elicit an allergic response.
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serology
The branch of immunology that studies blood serum and antigen–antibody reactions in vitro.
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serum sickness
A usually self-limiting immunological hypersensitivity reaction originally seen in response to the therapeutic injection of large amounts of foreign serum (now most usually evoked by the injection of drugs such as penicillin). It is caused by the formation of immune complexes of the antigen and the antibodies formed against it, which become deposited in the tissues, especially the kidneys.
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sipuleucel-T (Provenge)
Cell-based immunotherapy used to treat prostate cancer that combined prostatic acid phosphatase as a tumor rejection antigen presented by dendritic cells derived from a patient's monocytes. sirolimus See rapamycin.
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slide agglutination test
A method of identifying an antigen by combining it with a specific antibody on a slide.
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SLP-65
A scaffold protein in B cells that recruits proteins involved in the intracellular signaling pathway from the antigen receptor. Also called BLNK.
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SLP-76
A scaffold protein involved in the antigen-receptor signaling pathway in lymphocytes.
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spleen
An organ in the upper left side of the peritoneal cavity containing a red pulp, involved in removing senescent blood cells, and a white pulp of lymphoid cells that respond to antigens delivered to the spleen by the blood.
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Src-family protein tyrosine kinases
Receptor-associated protein tyrosine kinases characterized by Src-homology protein domains (SH1, SH2, and SH3). The SH1 domain contains the kinase, the SH2 domain can bind phosphotyrosine residues, and the SH3 domain can interact with proline-rich regions in other proteins. In T cells and B cells they are involved in relaying signals from the antigen receptor.
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staphylococcal enterotoxins (SEs)
Secreted toxins produced by some staphylococci, which cause food poisoning and also stimulate many T cells by binding to MHC class II molecules and the Vβ domain of certain T-cell receptors, acting as superantigens.
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subcapsular sinus (SCS)
The site of lymphatic entry in lymph nodes lined by phagocytes, including subcapsular macrophages which capture particulate and opsonized antigens draining in from tissues.
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supramolecular activation complex (SMAC)
Organized structure that forms at the point of contact between a T cell and its target cell, in which the ligand-bound antigen receptors are co-localized with other cell-surface signaling and adhesion molecules. Also known as supramolecular adhesion complex.
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surface immunoglobulin (sIg)
The membrane-bound immunoglobulin that acts as the antigen receptor on B cells.
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Syk
A cytoplasmic tyrosine kinase found in B cells that acts in the signaling pathway from the B-cell antigen receptor.
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T antigen
An antigen in the nucleus of a tumor cell.
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T helper (TH) cell
A specialized T cell that often interacts with an antigen before B cells interact with the antigen.
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T-cell-mediated immune response
Any adaptive immune response mediated by antigen-specific T cells.
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T-dependent antigen
An antigen that will stimulate the formation of antibodies only with the assistance of T helper cells. See also T-independent antigen.
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T-independent antigen
An antigen that will stimulate the formation of antibodies without the assistance of T helper cells. See also T-dependent antigen.
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TAP1, TAP2
Transporters associated with antigen processing. ATP-binding cassette proteins that form a heterodimeric TAP-1:TAP-2 complex in the endoplasmic reticulum membrane, through which short peptides are transported from the cytosol into the lumen of the endoplasmic reticulum, where they associate with MHC class I molecules.
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tertiary immune responses
Adaptive immune response provoked by a third injection of the same antigen. It is more rapid in onset and stronger than the primary response.
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thymic selection
Elimination of T cells that don’t recognize self antigens (major histocompatibility complex).
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thymus leukemia antigen (TL)
Nonclassical MHC class Ib molecule expressed by intestinal epithelial cells and a ligand for CD8α:α.
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thymus-dependent antigens (TD)
Antigens that elicit responses only in individuals that have T cells.
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thymus-independent antigens (TI)
Antigens that can elicit antibody production without the involvement of T cells. There are two types of TI antigens: the TI-1 antigens, which have intrinsic B-cell activating activity, and the TI-2 antigens, which activate B cells by having multiple identical epitopes that cross-link the B-cell receptor.
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tissue-resident memory T cells (TRM)
Memory lymphocytes that do not migrate after taking up residence in barrier tissues, where they are retained long term. They appear to be specialized for rapid effector function after restimulation with antigen or cytokines at sites of pathogen entry.
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tolerance
The failure to respond to an antigen. Tolerance to self antigens is an essential feature of the immune system; when tolerance is lost, the immune system can destroy self tissues, as happens in autoimmune disease.
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tolerant
Describes the state of immunological tolerance, in which the individual does not respond to a particular antigen.
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tolerogenic
Describes an antigen or type of antigen exposure that induces tolerance.
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toxic shock syndrome
A systemic toxic reaction caused by the massive production of cytokines by CD4 T cells activated by the bacterial superantigen toxic shock syndrome toxin-1 (TSST-1), which is secreted by Staphylococcus aureus.
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tumor rejection antigens
Antigens on the surface of tumor cells that can be recognized by T cells, leading to attack on the tumor cells. TRAs are peptides of mutant or overexpressed cellular proteins bound to MHC class I molecules on the tumor-cell surface.
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tumor-specific transplantation antigen (TSTA)
A viral antigen on the surface of a transformed cell.
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Type-specific antigen
Epitopes, defined by neutralizing antibodies, that distinguish and define viral serotypes (e.g., poliovirus types 1, 2, and 3). (Chapter 2)
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xenoimmunity
In the context of immune-mediated disease, refers to immunity directed against foreign antigens of non-human species, such as bacteria-derived antigens of the commensal microbiota that are targets in inflammatory bowel disease (IBD).
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Zeta-associated protein 70 (ZAP-70)
A protein kinase in T lymphocytes, activated by antigen binding to the T-cell receptor.
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α:β heterodimer
The dimer of one α and one β chain that makes up the antigen-recognition portion of an α:β T-cell receptor.
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γ:δ T cells
Subset of T lymphocytes bearing a T-cell receptor composed of the antigen-recognition chains, γ and δ, assembled in a γ:δ heterodimer.
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γ:δ T-cell receptors
Antigen receptor carried by a subset of T lymphocytes that is distinct from the α:β T-cell receptor. It is composed of a γ and a δ chain, which are produced from genes that undergo gene rearrangement.
