| AHA | acetohydroxamic acid; acquired hemolytic anemia; acute hemolytic anemia; American Heart Association;... |
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| AIA | allylisopropylacetamide; amylase inhibitor activity; anti-immunoglobulin antibody; anti-insulin anti... |
| ANA | acetylneuraminic acid; American Narcolepsy Association; American Neurological Association; American ... |
| APA | action potential amplitude; aldosterone-producing adenoma; Ambulatory Pediatric Association; America... |
| ATA | alimentary toxic aleukia; American Thyroid Association; aminotriazole; antithymic activity; antithyr... |
| antibody-dependent cell cytotoxicity | The phenomenon of antibody-mediated target cell destruction by non-sensitised effector cells. The identity of the target cell varies, but it must possess surface IgG whose fc portion is intact. The effector cell is a "killer" cell possessing fc receptors. It may be a lymphocyte lacking conventional b- or T-cell markers, or a monocyte, macrophage, or polynuclear leukocyte, depending on the identity of the target cell. The reaction is complement-independent. (12 Dec 1998) |
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| antibody-dependent enhancement | Enhancement of viral infectivity caused by non-neutralizing antibodies. There are at least two mechanisms known to account for this: mediation by fc receptors (receptors, fc) or by complement receptors (receptors, complement). Either the virus is complexed with antiviral IgG and binds to fc receptors, or virus is coated with antiviral IgM and binds to complement receptors. (12 Dec 1998) |
| Antibody Directed Enzyme Prodrug Therapy | <pharmacology> A method for targeting a drug to a specific tissue, in which the targeting agent and the drug are administered separately. The drug is designed to be inactive (a prodrug) until it is converted by an enzyme, which is the targeting agent. The enzyme is coupled to an antibody that directs it to the tissue of interest. When the enzyme arrives at the tissue, the prodrug is activated only at that site, sparing other tissues from potentially toxic side effects. Acronym: ADEPT (14 Nov 1997) |
| antibody diversity | The phenomenon of immense variability characteristic of antibodies, which enables the immune system to react specifically against the essentially unlimited kinds of antigens it encounters. Antibody diversity is accounted for by three main theories: 1) the germ line theory, which holds that each antibody-producing cell has genes coding for all possible antibody specificities, but expresses only the one stimulated by antigen; 2) the somatic mutation theory, which holds that antibody-producing cells contain only a few genes, which produce antibody diversity by mutation; and 3) the gene rearrangement theory, which holds that antibody diversity is generated by the rearrangement of variable region gene segments during the differentiation of the antibody-producing cells. (12 Dec 1998) |
| antibody excess | In a precipitation test, the presence of antibody in an amount greater than that required to combine with all of the antigen present. (05 Mar 2000) |
| antibody-forming cell | <immunology> B-cells (plasma cells) that are dedicated to producing secreted antibodies. (09 Feb 1998) |
| antibody induced lysis | <haematology> The term is imprecise and should not be used since there is confusion as to which mechanism is involved, i.e. Natural killing or complement lysis. See: complement lysis, natural killer cells. (09 Feb 1998) |
| antibody producing cell | <immunology> A lymphocyte of the B series synthesising and releasing immunoglobulin. Equivalent to plasmacyte and plasma cell. (18 Nov 1997) |
| antibody-producing cells | Cells of the lymphoid series that can react with antigen to produce specific cell products called antibodies. Various cell subpopulations, often B-lymphocytes, can be defined, based on the different classes of immunoglobulins that they synthesise. (12 Dec 1998) |
| antibody specificity | The property of antibodies which enables them to react with some antigenic determinants and not with others. Specificity is dependent on chemical composition, physical forces, and molecular structure at the binding site. (12 Dec 1998) |
| antibody technology | <molecular biology> Techniques for the synthesis of polyclonal and monoclonal antibodies for use in research, diagnostics and therapeutics. (09 Feb 1998) |
| antigen-antibody complex | The complex formed by the binding of antigen and antibody molecules. The deposition of large antigen-antibody complexes leading to tissue damage causes immune complex diseases. If the antigen is polyvalent the complex may be insoluble. Immune complexes activate complement through the classical pathway. See: glomerulonephritis, Arthus reaction, type III hypersensitivity. (12 Dec 1998) |
| antigen-antibody reaction | The phenomenon, occurring in vitro or in vivo, of antibody combining with antigen of the type that stimulated the formation of the antibody, thereby resulting in agglutination, precipitation, complement fixation, greater susceptibility to ingestion and destruction by phagocytes, or neutralization of exotoxin. See: skin test. (05 Mar 2000) |
| anti-idiotype antibody | <immunology> An antibody directed against the antigen specific part of the sequence of an antibody or T-cell receptor and thus recognise the binding sites of other antibodies. In principle an anti-idiotype antibody should inhibit a specific immune response and they are important to the regulation of the immune system. (13 Nov 1997) |
| anti-insulin antibody | A serologic blood test that is used to detect antibodies to insulin. This test is performed in insulin dependent diabetics who exhibit insulin resistance. The presence of antibodies denotes a positive result. (27 Sep 1997) |