| CD4-positive T-lymphocytes | A critical subpopulation of regulatory T-lymphocytes involved in the induction of most immunological functions. The HIV virus has selective tropism for the t4 cell which expresses the CD4 phenotypic marker, a receptor for HIV. In fact, the key element in the profound immunosuppression seen in HIV infection is the depletion of this subset of T-lymphocytes, which includes both the helper-inducer (T-lymphocytes, helper-inducer) and suppressor-inducer (T-lymphocytes, suppressor-inducer) T-cells. (12 Dec 1998) |
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| CD4/CD8 count | The ratio of the number of helper-inducer T lymphocytes to cytotoxic-suppressor T lymphocytes, as measured by monoclonal antibodies to the CD4 surface antigen found on helper-inducer T-cells, and the CD8 surface antigen found on cytotoxic-suppressor T-cells. In healthy individuals, the H/S ratio ranges between 1.6 and 2.2.When the body mounts an immune response, as against a virus or a transplant, the ratio is almost always reduced because of a decrease in the number of circulating helper-inducer cells and an increase in suppressor cells. The CD4/CD8 count has been used to monitor for signs of organ rejection after transplants, and more recently has become a tool for assessing the relative condition of HIV patients. With the CD4 absolute count and the CD4 lymphocyte percentage, it provides a way of gauging the progression from HIV to AIDS. (05 Mar 2000) |
| CD40 | <immunology> Differentiation antigens found on all mature B-lymphocytes and some epithelial cells, carcinomas, and lymphoid dendritic cells. This is a member of the tumour necrosis factor superfamily. Evidence suggests that CD40-dependent activation of B-cells is important for generation of memory B-cells within the germinal centres. (12 Dec 1998) |
| CD44 | <immunology> Acidic sulfated integral membrane glycoproteins expressed in several alternatively spliced and variable glycosylated forms on a wide variety of cell types including mature T-cells, B-cells, medullary thymocytes, granulocytes, macrophages, erythrocytes, and fibroblasts. Cd44 antigens are the principle cell surface receptors for hyaluronate and this interaction mediates binding of lymphocytes to high endothelial venules. (12 Dec 1998) |
| CD45 | <immunology> High-molecular weight glycoproteins uniquely expressed on the surface of all leukocytes and their haemopoietic progenitors. The CD45 family consists of multiple members that are all products of a single gene. Cd45 expression is necessary for signalling through the T-cell receptor. (12 Dec 1998) |
| CD45 phosphatase | <enzyme> Reverses glycoprotein cd3-induced microtubule-associated protein-2 kinase activity in jurkat t-cells Registry number: EC 3.1.3.- Synonym: glycoprotein-cd45 phosphatase, cd45 ptpase, cd45 phosphotyrosine phosphatase (26 Jun 1999) |
| CD4:CD8 ratio | The ratio of CD4 to CD8 cells. A common measure of immune system status that is around two in healthy individuals. The ratio of T-lymphocytes that express the CD4 antigen to those that express the CD8 antigen. This value is commonly assessed in the diagnosis and staging of diseases affecting the immune system including HIV infection. (12 Dec 1998) |
| CD5 | <immunology> Glycoproteins expressed on all mature T-cells, thymocytes, and a subset of mature B-cells. Antibodies specific for CD5 can enhance T-cell receptor-mediated T-cell activation. The B-cell-specific molecule CD72 is a natural ligand for CD5. (12 Dec 1998) |
| CD50 | <abbreviation> Curative dose. (05 Mar 2000) |
| CD55 | <immunology> Glycoproteins broadly distributed among haematopoietic and non-haematopoietic cells. Cd55 prevents the assembly of c3 convertase or accelerates the disassembly of preformed convertase, thus blocking the formation of the membrane attack complex. (12 Dec 1998) |
| CD56 | <immunology> The 140-kD isoform of ncam (neural cell adhesion molecule) containing a transmembrane domain and short cytoplasmic tail. It is expressed by all lymphocytes mediating non-MHC restricted cytotoxicity and is present on some neural tissues and tumours. (12 Dec 1998) |
| CD57 | <immunology> Oligosaccharide antigenic determinants found principally on nk cells and T-cells. Their role in the immune response is poorly understood. (12 Dec 1998) |
| CD58 | <immunology> Glycoproteins with a wide distribution on haematopoietic and non-haematopoietic cells and strongly expressed on macrophages. Cd58 mediates cell adhesion by binding to CD2 (antigens, CD2) and this enhances antigen-specific T-cell activation. (12 Dec 1998) |
| CD59 | <immunology> Small glycoproteins found on both haematopoietic and non-haematopoietic cells. Cd59 restricts the cytolytic activity of homologous complement by binding to c8 and c9 and blocking the assembly of the membrane attack complex. (12 Dec 1998) |
| CD7 | <immunology> Differentiation antigens expressed on pluripotential haematopoietic cells, most human thymocytes, and a major subset of peripheral blood T-lymphocytes. They have been implicated in integrin-mediated cellular adhesion and as signalling receptors on T-cells. (12 Dec 1998) |