| CD27 | <immunology> Dimeric membrane glycoproteins found on most T-lymphocytes. Activation of T-cells by the antigen receptor increases CD27 surface expression. (12 Dec 1998) |
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| CD28 | <immunology> T-cell differentiation antigens that serve as the receptors for the b7 antigen (antigens, CD80) which modulates T-cell lymphokine production. (12 Dec 1998) |
| CD29 | <immunology> Integrin beta-1 chains which are expresssed as heterodimers noncovalently associated with specific alpha-chains of the CD49 family (CD49a-f). Cd29 is expressed on resting and activated leukocytes and is a marker for total very late activation antigens on cells. (barclay et al., the leukocyte antigen factsbook, 1993, p164) (12 Dec 1998) |
| CD3 | <immunology> A complex of at least five membrane-bound polypeptides in mature T-lymphocytes that are non-covalently associated with one another and with the T-cell receptor (receptors, antigen, T-cell). The CD3 complex includes the gamma, delta, epsilon, zeta, and eta chains (subunits). When antigen binds to the T-cell receptor, the CD3 complex transduces the activating signals to the cytoplasm of the T-cell. The CD3 gamma and delta chains (subunits) are separate from and not related to the gamma/delta chains of the T-cell receptor (receptors, antigen, T-cell, gamma-delta). (12 Dec 1998) |
| CD30 | <immunology> Differentiation antigens normally present in a small number of cells in the lymph nodes and tonsils in vivo, but also capable of being induced in a wide range of cells in vitro. They are clinically useful as tumour markers for ki-1 lymphoma (lymphoma, large-cell, ki-1) and some cases of lymphomatoid papulosis, mycosis fungoides, and hodgkin's disease. (12 Dec 1998) |
| CD31 | <immunology> Cell adhesion molecules present on virtually all monocytes, platelets, and granulocytes. Cd31 is highly expressed on endothelial cells and concentrated at the junctions between them. (12 Dec 1998) |
| CD34 | <immunology> Glycoproteins found on immature haematopoietic cells and endothelial cells. They are the only molecules to date whose expression within the blood system is restricted to a small number of progenitor cells in the bone marrow. (12 Dec 1998) |
| CD36 | <immunology> Leukocyte differentiation antigens and major platelet membrane glycoproteins present on monocytes, endothelial cells, platelets, mammary epithelial cells, and a variety of cultured cell lines. They play major roles in adhesion phenomena, signal transduction, and haematopathology. Cd36 is also the receptor for thrombospondin and malaria-infected erythrocytes. (12 Dec 1998) |
| CD4 | <immunology> 55-kD glycoproteins originally defined as differentiation antigens on T-lymphocytes, but also found on other cells including monocytes/macrophages. CD4 antigens are members of the immunoglobulin supergene family and are implicated as associative recognition elements in MHC (major histocompatibility complex) class II-restricted immune responses. On T-lymphocytes they define the helper/inducer subset. Cd4 antigens also serve as HIV receptors, binding directly to the envelope protein gp120 on HIV. The protein structure on the surface of a human cell that allows HIV to attach, enter, and thus infect a cell. CD4 receptors are present on CD4 cells (helper T-cells), macrophages and dendritic cells, among others. Normally, CD4 acts as an accessory molecule, forming part of larger structures (such as the T-cell receptor) through which Tcells and other cells signal each other. (12 Dec 1998) |
| CD4 cell | T helper cells which are targets for HIV infection. (09 Oct 1997) |
| CD4 cell count | The most commonly used surrogate marker for assessing the state of the immune system. As CD4 cell count declines, the risk of developing opportunistic infections increases. The normal range for CD4 cell counts is 500 to 1500 per cubic millimetre of blood. CD4 count should be rechecked at least every six to twelve months if CD4s are greater than 500/mm3. If the count is lower, testing every three months is advised. (09 Oct 1997) |
| CD4 count, absolute | The number of helper T-lymphocytes in a cubic millimeter of blood. With HIV, the absolute CD4 count declines as the infection progresses. The absolute CD4 count is frequently used to monitor the extent of immune suppression in persons with HIV. Also called a T4 count. (12 Dec 1998) |
| CD4 immunoadhesins | <immunology> Chimeric molecules resulting from the fusion of recombinant soluble CD4 to the fc portion of immunoglobulins. These have potential use in the therapy of aids since they possess both the gp120-binding and HIV-blocking properties of rCD4 as well as the long plasma half-life and fc receptor-binding functions of immunoglobulin. (12 Dec 1998) |
| CD4 lymphocyte | A specific type of lymphocyte, derived from the thymus gland, that plays an important role in cellular immunity. T4 lymphocytes (CD4 cells) are decreased (absolute counts less than 200) in patients with AIDS resulting in compromised immune function. (27 Sep 1997) |
| CD4 lymphocyte count | A count of the number of CD4-positive lymphocytes in the blood. Determination requires the use of a fluorescence-activated flow cytometer. (12 Dec 1998) |