| O antigen | Somatic antigen of enteric gram-negative bacteria. External part of cell wall lipopolysaccharide. See: H antigen. See ABO blood group, Blood Groups appendix. (05 Mar 2000) |
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| O-antigen depolymerase | <enzyme> Cleaves surface o-polysaccharide (o-antigen)of salmonella anatum Registry number: EC 3.2.1.- (26 Jun 1999) |
| O-antigen polymerase | <enzyme> Involved in the binding of o-antigen repeat units and in polymerizing into the o-antigen chain; mw 43.7 kD; genbank x71970 Registry number: EC 2.4.1.- Synonym: rfc protein, s. Flexneri, rfc gene product, o-antigen polymerase, shigella, o-antigen polymerase, pseudomonas, rfc protein, pseudomonas, o-antigen polymerase, e. Coli (26 Jun 1999) |
| organ-specific antigen | A heterogenetic antigen with organ specificity; e.g., in addition to species-specific antigen, kidney of one species contains antigen that is identical to that in kidney of other species. Synonym: tissue-specific antigen. (05 Mar 2000) |
| Tac antigen | An antigenic determinant of the human interleukin 2 receptor that is identified by a murine monoclonal antibody, anti-Tac. Binding of this antigen prevents the proliferation of T-cells, which is normally stimulated by binding interleukin-2. (05 Mar 2000) |
| T antigen | <molecular biology> Proteins coded by viral genes that are expressed early in the replication cycle of papovaviruses such as SV40 and polyoma. Essential for normal viral replication, they are also expressed in nonpermissive cells transformed by these viruses. Originally detected as Tumour antigens by immunofluorescence with antisera from tumour bearing animals. SV40 has two, large T and small t, polyoma has three, large, middle and small. Appear to be collectively responsible for transformation by these viruses. (14 Oct 1997) |
| T-cell antigen receptors | Receptors present on T-cells that interact with both processed antigen and major histocompatibility antigens simultaneously. (05 Mar 2000) |
| T-dependent antigen | An antigen that requires T helper cells in addition to appropriate B-cells. Most antigens are T-dependent. (05 Mar 2000) |
| theta antigen | A surface glycoprotein that is present on thymocytes of mice and rats. (05 Mar 2000) |
| thymus-independent antigen | An antigen that does not require T helper cell activation in order for the host's B-cells to be stimulated. Repeating polymers such as polysaccharides are examples of T-independent antigens. (05 Mar 2000) |
| tissue polypeptide antigen | Serological tumour marker composed of a molecular complex of cytokeratins 8, 18, and 19. It is used in the diagnosis and staging of bronchogenic carcinoma. (12 Dec 1998) |
| tissue-specific antigen | A heterogenetic antigen with organ specificity; e.g., in addition to species-specific antigen, kidney of one species contains antigen that is identical to that in kidney of other species. Synonym: tissue-specific antigen. (05 Mar 2000) |
| TL antigen | <immunology> The mouse antigens coded for by the TLa complex, in normal animals only found on intrathymic lymphocytes, but also seen on leukaemic cells (hence, thymus leukaemia antigen) in certain forms of the disease in mice. The molecules have structures similar in some ways to Class I MHC products but are disulphide bonded tetramers of two 45 kD chains and two 12 kD chains of _2 microglobulin type. (18 Nov 1997) |
| transplantation antigen | <immunology> Any antigen that is antigenically active in graft rejection. In practice the major histocompatibility complex and the H Y antigens and to a lesser extent minor histocompatibility antigens. (18 Nov 1997) |
| Epithelial membrane antigen | <cell biology> Heavily glycosylated membrane glycoprotein. Encoded by the MUC 1 gene, has a molecular weight of around 300 kD, more than half of which is O linked glycan. There is a 69 residue cytoplasmic domain and the extracellular domain may extend hundreds of nanometres beyond the plasma membrane, the increased expression in carcinoma cells may reduce the adhesion and mask antigenic properties of the cells. Similar functions are ascribed to ASGP, epiglycanin and leucosialin. (18 Nov 1997) |