| cytotoxicity | The quality or state of being cytotoxic. Antibody-dependent cell-mediated cytotoxicity (ADCC), a form of lymphocyte-mediated cytotoxicity that functions only if antibodies are bound to the target cell. Lymphocyte-mediated cytotoxicity, the toxic or lytic activity of T-lymphocytes, which may or may not be mediated by antibodies. Cytotoxic T lymphocytes may cause lysis of cells by production of cytolytic proteins such as perforin. B-cells may cause lysis of cells by antibody-complement binding to a target cell. Natural killer cells are cytotoxic without prior sensitization. Toxicity by lymphocytes may also be mediated by antibodies; there are three kinds of cytotoxic T-lymphocytes: those that are antigen-specific as a result of previous allergization (immunization), killer cells, and natural killer cells. See: antibody-dependent cell-mediated cytotoxicity. (05 Mar 2000) |
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| cytotoxicity tests, immunologic | The demonstration of the cytotoxic effect on a target cell of a lymphocyte, a mediator released by a sensitised lymphocyte, an antibody, or complement. (12 Dec 1998) |
| cytotoxicity, immunologic | The phenomenon of target cell destruction by immunologically active effector cells. It may be brought about directly by sensitised T-lymphocytes or by lymphoid or myeloid "killer" cells, or it may be mediated by cytotoxic antibody, cytotoxic factor released by lymphoid cells, or complement. (12 Dec 1998) |
| antibody-dependent cell cytotoxicity | The phenomenon of antibody-mediated target cell destruction by non-sensitised effector cells. The identity of the target cell varies, but it must possess surface IgG whose fc portion is intact. The effector cell is a "killer" cell possessing fc receptors. It may be a lymphocyte lacking conventional b- or T-cell markers, or a monocyte, macrophage, or polynuclear leukocyte, depending on the identity of the target cell. The reaction is complement-independent. (12 Dec 1998) |
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