| variable antigen | <immunology> Term usually applied to the surface antigens of those parasitic or pathogenic organisms that can alter their antigenic character to evade host immune responses. (See antigenic variation). (18 Nov 1997) |
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| G antigen | An antigenic glycoprotein frequently associated with viral surfaces. Origin: Ger. Gebundenes, bound (05 Mar 2000) |
| major histocompatibility antigen | <immunology> A set of plasmalemmal glycoprotein antigens involved in rapid (e.g. 7 days in the mouse) graft rejection and other immune phenomena. The minor histocompatibility antigens are involved in much slower rejection phenomena. The major antigens show remarkable polymorphism and occur as Class I and Class II types in mammals, birds may have a Class III molecule as well. See: histocompatibility antigens, MHC restriction. (18 Nov 1997) |
| P antigen | <haematology, immunology> Antigenic determinant on the surface of human red blood cells to which the Donath Landsteiner antibody reacts. This antibody binds in the cold (a cold IgG), but elutes from red cells at 37쵣, is particularly associated with tertiary syphylis and its binding causes paroxysmal nocturnal haemoglobinuria. (18 Nov 1997) |
| R antigen | Those that produce active haemolysins (O and S) which cause a zone of clear haemolysis on the blood agar medium in the area of the colony; beta-haemolytic streptococci are divided into groups (A to O) on the basis of cell wall C carbohydrate (see Lancefield classification); Group A (in the strains pathogenic for man) comprises more than 50 types (designated by Arabic numerals) determined by cell wall M protein, which seems to be associated closely with virulence and is produced chiefly by strains with matt or mucoid colonies, in contrast to nonvirulent, glossy colony-producing strains; other surface protein antigens such as R and T (T substance), and the nucleoprotein fraction (P substance) seem to be of less importance. The more than 20 extracellular substances elaborated by strains of beta-haemolytic streptococci include erythrogenic toxin (elaborated only by lysogenic strains), deoxyribonuclease (streptodornase), haemolysins (streptolysins O and S), hyaluronidase, and streptokinase. Synonym: haemolytic streptococci. (05 Mar 2000) |
| gene rearrangement, alpha-chain T-cell antigen receptor | Ordered rearrangement of T-cell variable gene regions coding for the alpha-chain of antigen receptors. (12 Dec 1998) |
| gene rearrangement, beta-chain T-cell antigen receptor | Ordered rearrangement of T-cell variable gene regions coding for the beta-chain of antigen receptors. (12 Dec 1998) |
| gene rearrangement, delta-chain T-cell antigen receptor | Ordered rearrangement of T-cell variable gene regions coding for the delta-chain of antigen receptors. (12 Dec 1998) |
| gene rearrangement, gamma-chain T-cell antigen receptor | Ordered rearrangement of T-cell variable gene regions coding for the gamma-chain of antigen receptors. (12 Dec 1998) |
| M antigen | An antigen found in the cell of Streptococcus pyogenes; associated with virulence. See: beta-haemolytic streptococci. (05 Mar 2000) |
| receptor-CD3 complex, antigen, T-cell | Molecule composed of the non-covalent association of the T-cell antigen receptor (receptors, antigen, T-cell) with the CD3 complex (antigens, CD3). This association is required for the surface expression and function of both components. The molecule consists of up to seven chains: either the alpha/beta or gamma/delta chains of the T-cell receptor, and four or five chains in the CD3 complex. (12 Dec 1998) |
| receptors, antigen | Molecules on the surface of b- and T-lymphocytes that recognise and combine with specific antigens. (12 Dec 1998) |
| receptors, antigen, B-cell | Immunoglobulin molecules on the surface of B-lymphocytes that recognise and bind antigen. (12 Dec 1998) |
| receptors, antigen, T-cell | Molecules on the surface of T-lymphocytes that recognise and combine with antigens. The receptors are non-covalently associated with a complex of several polypeptides collectively called CD3 antigens (antigens, CD3). Recognition of foreign antigen and the major histocompatibility complex is accomplished by a single heterodimeric antigen-receptor structure, composed of either alpha-beta (receptors, antigen, T-cell, alpha-beta) or gamma-delta (receptors, antigen, T-cell, gamma-delta) chains. (12 Dec 1998) |
| receptors, antigen, T-cell, alpha-beta | T-cell receptors composed of CD3-associated alpha and beta polypeptide chains and expressed primarily in CD4+ or CD8+ T-cells. Unlike immunoglobulins, the alpha-beta T-cell receptors recognise antigens only when presented in association with major histocompatibility (MHC) molecules. (12 Dec 1998) |