| T suppressor cell | <haematology, immunology> Set of T lymphocytes (usually CD8) specifically involved in suppressing B-cell differentiation into antibody secreting cells. There may also be T suppresors of T-cell functions. (18 Nov 1997) |
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| T system | The transverse tubules that are continuous with the sarcolemma in skeletal and cardiac muscle fibres. (05 Mar 2000) |
| t test | A test that uses a statistic which under the null hypothesis has the t distribution, to test whether two means differ significantly. (05 Mar 2000) |
| T tube | A self-retaining tube with side extensions, shaped like a tube. (05 Mar 2000) |
| T tubule | <cell biology> Invagination of the plasma membrane (sarcolemma) of striated muscle that lies between two tubular portions of the endoplasmic (sarcoplasmic) reticulum to form a triad of membrane profiles adjacent to the A band/I band junction in some cases, in other cases to the Z disc, of the resting sarcomere. Depolarisation of the T tubule membrane triggers the release of calcium from the sarcoplasmic reticulum and eventually muscle contraction. (18 Nov 1997) |
| T wave | The next deflection in the electrocardiogram following the QRS complex; represents ventricular repolarization. (05 Mar 2000) |
| t-2 toxin | <chemical> (3 alpha,4 beta,8 alpha)-12,13-epoxytrichothec-9-ene-3,4,8,15-tetrol 4,15-diacetate 8-(3-methylbutanoate). A potent mycotoxin produced in feedstuffs by several species of the genus fusarium. It elicits a severe inflammatory reaction in animals and has teratogenic effects. Chemical name: Trichothec-9-ene-3,4,8,15-tetrol, 12,13-epoxy-, 4,15-diacetate 8-(3-methylbutanoate), (3alpha,4beta,8alpha)- (12 Dec 1998) |
| T-bandage | t-binder |
| t-butoxycarbonyl | (CH3)3COCO-;an amino-protecting group used in peptide synthesis. Synonym: tert-butyloxycarbonyl. (05 Mar 2000) |
| T-cell | <haematology, immunology> A class of lymphocytes, so called because they are derived from the thymus and have been through thymic processing. Involved primarily in controlling cell-mediated immune reactions and in the control of B-cell development. The T-cells coordinate the immune system by secreting lymphokine hormones. There are 3 fundamentally different types of t cells : helper, killer, and suppressor. Each has many subdivisions. T-cells are also called t lymphocytes. They bear T-cell antigen receptors (CD3) and lack Fc or C3b receptors. Major T-cell subsets are CD4 (mainly helper cells) and CD8 (mostly cytotoxic or suppressor T-cells). Uncontrolled proliferation of this type of cell gives rise to T-cell leukaemia/lymphoma. (21 Jun 1999) |
| T-cell antigen receptors | Receptors present on T-cells that interact with both processed antigen and major histocompatibility antigens simultaneously. (05 Mar 2000) |
| T-cell growth factor | <cytokine> A hormone-like substance released by stimulated T lymphocytes, causes activation and differentiation of other T lymphocytes independently of antigen. A type of interleukin, a chemical messenger, a substance that can improve the body's response to disease. It stimulates the growth of certain disease-fighting blood cells in the immune system. It is secreted by Thl CD4 cells to stimulate CD8 cytotoxic T-1yrnphocytes. Interleukin 2 also increases the proliferation and maturation of the CD4 cells themselves. During HIV infection, Interleukin-2 production gradually declines. Use of interleukin 2 therapy is under study as a way to raise CD4 cell counts and restore immune function. Acronym: IL-2 (12 Dec 1998) |
| T-cell growth factor-1 | <cytokine> A hormone-like substance released by stimulated T lymphocytes, causes activation and differentiation of other T lymphocytes independently of antigen. A type of interleukin, a chemical messenger, a substance that can improve the body's response to disease. It stimulates the growth of certain disease-fighting blood cells in the immune system. It is secreted by Thl CD4 cells to stimulate CD8 cytotoxic T-1yrnphocytes. Interleukin 2 also increases the proliferation and maturation of the CD4 cells themselves. During HIV infection, Interleukin-2 production gradually declines. Use of interleukin 2 therapy is under study as a way to raise CD4 cell counts and restore immune function. Acronym: IL-2 (12 Dec 1998) |
| T-cell growth factor-2 | <cytokine> A soluble cytokine factor produced by activated T-lymphocytes that promotes antibody production by causing proliferation and differentiation of B-cells. Interleukin-4 induces the expression of class II major histocompatibility complex and fc receptors on B-cells. It also acts on T-lymphocytes, mast cell lines, and several other haematopoietic lineage cells including granulocyte, megakaryocyte, and erythroid precursors, as well as macrophages. Acronym: IL-4 (12 Dec 1998) |
| T-cell leukaemia virus | human T-lymphotropic virus |