ABC: Antigen-binding cell.

ABS: Antigen-binding site on an antibody.

ADCC: Antibody-dependent cell-mediated cytotoxicity.

Adjuvant: A substance which intensifies the immune response against an antigen, in a immunologically non-specific manner.

AFC: Antibody-forming cell.

Affinity: A measure of binding strength between an antigen determinant (epitope) and the binding site of an antibody (paratope).

Affinity maturation: An increase in the average antibody affinity acquired during the course of a secondary and following immune responses.

AFP: a-fetoprotein.

Allele: Gene locus variations within a species.

Allergy: An altered response following secondary contact with the same antigen, also defined as type I hypersensi-tivity.

Allogeneic: Refers to the genetic variety contained within a species.

Allotransplant: Transplanted allogeneic tissue.

Allotype: Different forms of a protein product, usually Ig, recognized as an antigen by another individual of the same species.

Alternative pathway: Activation of the complement system via C3 or other factors, but not via Clq.

ANA (anti-nuclear antibodies): Autoantibody directed against DNA contained within the cell nucleus.

Anaphylatoxins: Complement fragments (C3a and C5a), responsible for mediating mast cell degranulation.

Anaphylaxis: An antigen-specific, primarily systemic IgG- or IgE-mediated-im-mune response.

Antigens: Molecules which are usually characterized by complex folding, and which can be recognized by antibodies.

Antibody: A molecule which binds to a specific antigen.

APC: Antigen-presenting cell.

Atopic: Increased susceptibility to the clinical manifestations associated with type I hypersensitivity (e.g. eczema, asthma, and rhinitis).

Autologous: Derived from the same individual (or inbred strain).

Autosomes: All chromosomes other than the X or Y sex chromosomes.

Avidity: A measure of the functional binding strength between an antibody and its antigen; dependent on affinity and valences (number of binding sites).

BCA-1: B-cell attractant.

BCG: Bacillus Calmette-Guerin. An attenuated form of Mycobacterium tuberculosis.

BCGF: B-cell growth factor.

Bence-Jones proteins: Free light chains of Ig present in the serum and urine of multiple myeloma patients.

Bursa fabricii: Lymphoepithelial organ adjacent to the cloaca of birds, in which B cells mature.

C domain: Constant component of Ig.

C3b inactivator: A component of the complement system, known as factor I.

Capping: Aggregation of surface molecules on the cell membrane.

Carrier: The part of a molecule which is recognized by T cells during an immune response.

CBR: Complement-binding reaction.

CCR: A receptor for those chemokines which contain adjacent cysteine-cy-steines (CXC or CXXC, cysteines separated by one or two amino acids).

CD marker: Cluster determinant or cluster of differentiation, characteristic of distinct lymphocyte subpopulations.

CDR: Complementarity determining regions (hypervariable antibody regions).

Chemokines: Chemoattractant cytokines

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Chimera: A single host bearing cells derived from genetically distinct individuals.

CLIP: A protein which blocks the binding groove of MHC class II prior to its inclusion in the phagolysosome (class II-in-hibiting protein).

CMI: Cell-mediated immunity.

Cobra venom factor: A component of cobra venom which exhibits enzymatic activity corresponding to the activity of mammalian C3b.

Combining site: The configuration on an antibody which forms a link with antigen determinants (ABS).

Complement system: A group of serum proteins that are activated in cascades; usually via antibodies, but in some cases directly by infectious agents. Plays an important role during inflammation, chemotaxis, cytolysis, and phagocytosis.

Con A (concanavalin A): AT-cell mitogen.

Cryoglobulin: Antibodies in immune complexes that can be precipitated at 4 °C

CSF: Colony-stimulating factor (also: cere-brospinal fluid).

CTL: Cytotoxic CD8+ Tcell.

CXCR: Receptor for those chemokines which contain a cysteine-x-cysteine motif.

Cyclophosphamide: A toxic substance frequently used to induce immuno-suppression.

Cyclosporine A: An immunosuppressant used for the prevention of rejection reactions.

Cytophilic: Exhibiting an affinity towards cells (i.e., binds to cells).

Cytostatic: Exhibiting an inhibitory effect on cell proliferation.

Cytotoxic: Exhibiting a destructive effect towards target cells.

DARC: Duffy antigen receptor for chemo-kines.

Dendritic cells: Professional APCs derived from the bone marrow. Dendritic cells are mobile and function to transport antigen into lymphoid organs. In the skin they are known as Langerhans cells, on the way to the lymph nodes veiled cells, and in the lymph nodes in-terdigitating cells.

Desensitization: Repeated exposure to small amounts of an antigen, against which the host shows an allergic reaction; the aim being to downregu-late IgE production and upregulate IgG production.

DiGeorge syndrome: Congenital thymic hypoplasia.

DNP: Dinitrophenol, a frequently used small hapten.

Domain: A peptide region with a stable tertiary structure. Immunoglobulins (Ig), MHC class I, and MHC class II molecules all contain comparable Ig domains.

DTH: Delayed type hypersensitivity; A delayed cellular type IV response.

EAE: Experimental allergic encephalitis.

ELISA: Enzyme-linked immunosorbent assay.

ELISPOT: A modified ELISA method used for the detection of specific cell secretion products.

Endotoxins: Bacterial toxins; largely comprised by lipopolysaccharides (LPS) from Gram-negative bacteria.

Eotaxin: A chemokine which regulates eo-sinophil migration.

Epitope: A special region within an antigen, which is recognized by an antibody binding site.

Epstein-Barr virus: A herpes virus capable of transforming human B cells, and for which B cells possess a special receptor (EBVR). The causative agent of infectious mononucleosis (Pfeiffer disease).

Exon: A protein-coding gene fragment.

Fab: The part of the antibody molecule which contains the antigen-binding site following treatment with papain; comprises a light chain and the first two domains of the heavy chain.

FACS: Fluorescence-activated cell sorter.

Fc: Antibodies use the Fc fragment to bind to cellular receptors (FcR) and C1q complement components.

FcR: Fc receptor.

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Fractalkine: A chemokine expressed by endothelial cells; has effects on inflammation and other processe.

Freund's adjuvant (FA): A water-in-oil emulsion. Complete FA contains killed Mycobacterium tuberculosis, whilst incomplete FA does not.

GALT: Gut-associated lymphoid tissue.

Gammaglobulins: The serum fraction which migrates most rapidly towards the anode during electrophoresis. Contains all five classes of immunoglo-bulins.

Gel diffusion test: Immunoprecipitation test; Antigens and antibodies diffuse towards one another, forming a stain-able precipitate at the equivalence zone (Ouchterlony test).

Germ line: The genetic material of gametes. Mutations in the germ line, unlike somatic mutations, are inherited by progeny.

GVH: Graft-versus-host reaction; rejection of host tissue by transplanted cells.

H-2: Main histocompatibility complex of mice.

Haplotype: The set of genetic determinants present on one chromosome or chromosome set.

Hapten: A small molecule which can function as an epitope by itself, without being coupled to a carrier, but which alone does not elicit an antibody response.

Helper cells: The CD4+ subclass of T cells which are functionally important for B cells, and which release cytokines; a single helper T-cell clone is specific for one peptide presented by a specific MHC class II molecule.

Hereditary angioedema: Result of congenital C1 inhibitor deficiency.

Heterologous: Belonging to another species.

HEV: High endothelial venules; these are specialized to allow the movement of lymphocytes from the blood into the lymph nodes.

High responder: Individuals (or inbred strains) which exhibit a strong immune response against a defined antigen.

Hinge region: The segment of an immunoglobulin heavy chain which lies between the Fc and Fab regions.

Histocompatibility: Quality which determines rules of acceptance or rejection of a transplant.

HLA: Human leukocyte antigen coded for by the human major histocompatibil-ity gene complex (MHC).

Homologous: Belonging to the same species.

Humoral: Any factor present within extracellular body fluids (e.g. serum, lymph).

HVG: Host-versus-graft reaction. Rejection of transplanted cells by host tissue.

Hybridoma: An antigen-specific B cell that has been successfully fused with a myeloma cell.

Hypervariable region: The three most variable segments present within the V domains of immunoglobulins and T-cell receptors.

Idiotype: The antigenic characteristic of the ABS region of an antibody.

IFN: Interferons; cellular derived substances which contribute to nonspecific cellular resistance, particularly with regard to viral infections.

IL: Interleukins; short-lived substances which mediate the transfer of information between distinct cells (both of the immune system and other tissues).

Immune complex: The product of an antigen-antibody reaction; may also contain components of the complement system.

Immune paralysis: Temporary inability to produce a specific immune response usually resulting from the presence of excessive antigen.

Immunity: Actively or passively acquired immune protection against pathogens and other antigens.

Immunoconglutinins: Auto-antibodies directed against complement components.

Immunofluorescence: Rendering certain antigens visible by binding of a specific fluorescence-labeled antibody.

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Immunogen: Any substance which can elicit a specific immune response.

Immunological memory: The ability to produce a faster and stronger immune response following a second, or subsequent, encounter with the same antigen.

Intron: The gene segment present between two exons.

Ir genes: Immune response genes; an early designation used for MHC genes. These code for MHC molecules which control peptide presentation, and thus directly determine the specificity and strength of an immune response.

Isologous: Of identical genetic constitution.

Isotype: The "isotypic" variants of certain proteins coded within the genome, which are identical for all individuals of a species (e.g., immunoglobulin classes).

J genes: Joining genes; a set of gene segments contained within the genetic loci of the heavy and light immunoglobulin chains, or T-cell receptor chains.

K cells: Killer cells; a group of lymphocytes bearing Fc receptors which can destroy their target cells by means of antibody-dependent cell-mediated cytotoxicity (ADCC).

Kupffer cells: Phagocytic cells present in the hepatic sinusoids.

LAK: Lymphokine-activated killer cells (lymphocytes).

LARC: Liver and activation-regulated che-mokine.

LCM: Lymphocytic choriomeningitis; an non-bacterial, viral, meningitis.

LGL: Large granular lymphocyte.

Low responder: Individuals (or inbred strains) which exhibit a weak immune response against a given antigen.

LPS: Lipopolysaccharide; a component of the cell wall of certain Gram-negative bacteria, which acts as a B-cell mitogen.

MALT: Mucosa-associated lymphoid tissue.

MBP: Myelin basic protein; functions as an antigen in experimental allergic encephalitis (and probably in multiple sclerosis).

MCP: Monocyte chemoattractant protein.

MDC: Macrophage-derived chemokine.

MHC: Major histocompatibility complex; the main genetic complex responsible for determining histocompatibility. This gene complex codes for the most important transplantation antigens (HLA antigens) in humans. MHC class I molecules are associated with b2 microglobulin, class II molecules consist of two noncovalently bound transmembrane molecules. The actual function of MHC I, and MHC II, molecules is to present anti-genic peptides on the cell surface. Class III molecules comprise complement components, cytokines, and so on.

MHC restriction: Resulting from the interaction of T lymphocytes with other cells, and being controlled by recognition of MHC-presented peptides by the TCR.

MIF: Migration inhibition factors; a group of peptides produced by lymphocytes which inhibit macrophage migration.

MIG: A monokine induced by interferon gamma.

P2 microglobulin: A protein component of MHC class I molecules.

MIP: Macrophage inflammatory protein.

Mitogen: Any substance which can alone stimulate cells, particularly lymphocytes, to undergo cell division.

MLC: Mixed lymphocyte culture. An in-vi-tro assay which measures the stimulation response of lymphocytes as allor-eactive cytotoxic T-cell reactivity.

MLR: Mixed lymphocyte reaction. An in-vi-tro assay which measures the stimulation response of lymphocytes as allor-eactive proliferation (determined by 3H-thymidine incorporation).

Monoclonal: Any substance derived from a single cell clone, for example monoclonal antibodies.

Myeloma: A B-cell lymphoma, which produces antibodies (plasmocytoma).

NK cells: Natural killer cells. Non-MHC-restricted lymphocytes capable of recognizing and destroying certain cells

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that are either virally infected or tumorous.

Nude mice: A mouse strain which carries a spontaneous mutation resulting in the animals having no hair, and usually being athymic.

NZB/W: A strain of mouse bred as an animal model for systemic lupus erythe-matosus.

Opsonization: Depositions of proteins on an infectious pathogen, that facilitate phagocytosis of the pathogen (e.g., antibodies and C3b).

Paratope: The part of an antibody molecule which contacts the antigenic determinant (epitope); the antigen-binding site (ABS) on the antibody.

PC: Phosphorylcholine; a commonly used hapten found on the surface of a number of microorganisms.

PCA: Passive cutaneous anaphylaxis; a classic detection reaction for antigen-specific IgE.

PFC: Plaque forming cell; an antibody-producing cell which can be detected by the hemolysis plaque test.

PHA: Phytohemagglutinin; a mitogen for T cells.

Plasma cell: An antibody-producing B cell which has reached the end of its differentiation pathway.

PMN: Polymorphonuclear neutrophilic granulocytes.

Pokeweed mitogen: A mitogen for B cells.

Polyclonal: A term describing products derived from a number of different cell clones (e.g., polyclonal antibodies).

Primary lymphoid tissues: Thymus, bursa of Fabricius (in birds), bone marrow.

Primary response: The immune response which follows an initial encounter with a particular antigen (see priming, secondary response).

Priming: Following an initial contact with an antigen, an immunocompetent cell becomes sensitized or "primed."

Prozone phenomenon: Lack of a measurable response at high-test substance concentrations.

Pseudoalleles: Tandem variants of a gene, which do not occupy a homologous position on the chromosome.

Pseudogenes: Genes containing structures which are homologous to other genes, but which cannot be expressed.

RANTES: Regulated on activation; this is normally expressed and secreted by T cells.

Reagin: Historical term for IgE.

Rearrangement: For instance the rearrangement of genetic information in somatic B and T cells.

Recombination: A process by which genetic information is rearranged during meiosis.

Reticuloendothelial system (RES): Phagocytic cells distributed within the supportive connective tissue of the liver, spleen, lymph nodes, and other organs (e.g. sinus endothelial cells, Kupf-fer cells, histiocytes).

Rhesus (Rh) antigens: Antigenic proteins present on the surface of erythrocytes in approximately 85% of all humans.

Rheumatoid factor (RF): Autoantibo-dies—these are usually IgM but can also be of the IgG and IgA isotypes— which are specifically directed against the body's own IgG molecules.

SCID: Severe combined immunodeficiency disease; a congenital deficiency of the humoral and cellular immune system, resulting from a lack of both T and B cells. The animal model is the SCID mouse and is a spontaneous mutant.

SDF-1alpha: Stromal cell-derived factor.

Secretory piece: An IgA-associated poly-peptide produced by epithelial cells, and which facilitates the transmembrane transport of IgA.

Secondary response: The immune response which follows a second encounter with a specific antigen.

Serum sickness: An inflammatory type III reaction, occurring after repeated injection of a foreign protein.

SLC: Secondary lymphoid organ chemo-kine.

SLE: Systemic lupus erythematosus.

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Somatic mutation/recombination: Rearrangements of genes in somatic cells (as opposed to germ line cells), resulting in a newly combined DNA sequence which is not heritable.

Splenomegaly: Splenic enlargement; often observed in cases of hematopoie-tic cell tumors, vascular circulatory problems, or following various parasitic infections. Can also be used as a measure of GVH reactions.

SRBC: Sheep red blood cells (erythrocytes).

Stripping: The process by which antibodies remove antigen determinants from target cells.

Suppressor cell: A proposed antigen-specific T-cell subpopulation which acts to reduce the immune responses of other T cells or B cells. This suppression can also be of a nonspecific nature.

Syngeneic: Animals produced by repeated inbreeding, or monozygotic twins, which are considered syngeneic when each pair of autosomes within the individuals is identical.

TATA: Tumor-associated transplantation antigens.

TCGF: T-cell growth factor; identical with interleukin 2 (IL-2).

T-dep/T-ind: T cell-dependent/T cell-independent; an antibody response to T-dependent antigens is only possible if (MHC-restricted) T-cell help is also available.

T-DTH: AT cell that contributes to delayed type hypersensitivity reactions.

TECK: Thymus-expressed chemokine.

Tetramer: Biotinylated MHC class I, or class II, molecule complexed to pep-tide and bound to labeled avidin. Used to determine the presence of peptide-specific T cells.

TGF: Transforming growth factor.

TH: T helper cells (CD4+ T cell; see also Helper cells).

Thy: A cell surface antigen of mouse T cells; there are several allelic variants of this marker.

TNF: Tumor necrosis factor.

Tolerance: A state of specific immunologi-cal unresponsiveness.

Transformation (blastic): Morphological changes in a lymphocyte associated with the onset of cell division.

Transplantation antigens: See MHC.

Wiskott-Aldrich syndrome: A sex-linked, inheritable, recessive, combined immune deficiency in which IgM antibody production and cellular immune reactions are impaired.

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