| AIA | allylisopropylacetamide; amylase inhibitor activity; anti-immunoglobulin antibody; anti-insulin anti... |
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| 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... |
| EA | early antigen; educational age; egg albumin; electric affinity; electrical activity; electroacupunct... |
| 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) |
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| 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) |
| antinuclear antibody | <immunology> Antinuclear antibody is an antibody that react against components of the cell nucleus such as DNA, RNA, histone or non-histone proteins. These antibodies are present in a variety of immunologic or autoimmune diseases including systemic lupus erythematosus, systemic sclerosis, scleroderma, Sjogren's syndrome, rheumatoid arthritis, polymyositis, dermatomyositis and in persons taking hydralazine, procainamide or isoniazid. A serologic measurement for antinuclear antibodies can aid in the diagnosis of unexplained arthritis, rashes or chest pains. Acronym: ANA (12 Jan 1998) |
| anti-P antibody | <haematology, investigation> A serologic blood test used to detect the Donath-landsteiner antibody in serum. This test is performed in cases of suspected paroxysmal cold haemoglobinuria. A normal result is indicated by an absence of antibodies. The antibody is directed toward the P-antigen complex which is located on the surface of red blood cells. In some way, cold temperatures trigger the antibody to bind to this site. (13 Jan 1998) |
| antiparietal cell antibody | <immunology> A serologic blood test which measures the presence of antibodies to gastric parietal cells. Less than 2% of the general population will be antibody positive although this can be higher in the elderly. Approximately 90% of individuals with pernicious anaemia will be antibody positive. A positive result may also be seen in atrophic gastritis, gastric ulcer, thyroid disease, iron deficiency anaemia and diabetes. (13 Jan 1998) |