title: Natural killer-like activity mediated by activated T lymphocytes.
abstract: Diverse types of lymphocytes mediate in vitro cytotoxic activity. In addition to CTLs (cytotoxic T lymphocytes) and NK (natural killer) cells which differ in their activation requirements, target specificities, and lytic mechanisms, a natural killer-like activity of activated cells (A-NK) has recently been described. The data presented here suggest that an activated T lymphocyte can mediate A-NK activity. A-NK activity can be separated from resting NK activity by its requirement for activation and an effector phenotype (T12+,Ia+,Mol-) which includes the presence of the T12 and Ia antigens and the absence of the Mol antigen. In contrast, resting NK activity is mediated by T12-,Ia-,Mol+ cells. Cells that mediate A-NK activity can be differentiated from CTLs by their differing kinetics of activation and susceptibility to inhibition by monoclonal antibodies. An additional distinguishing feature is the fact that A-NK cells are predominantly Ia+ and are derived from either the T4+ or T8+ T-cell subsets whereas CTLs generated under similar conditions are predominantly T8+,T4-,Ia-. The in vivo relevance of this newly defined T-cell cytolytic activity remains to be defined.
mesh_terms: D000911:Antibodies, Monoclonal / Q000276:immunology; D000954:Antigens, Surface / Q000032:analysis; D003602:Cytotoxicity, Immunologic; D006801:Humans; D007111:Immunity, Cellular; D007113:Immunity, Innate; D007694:Killer Cells, Natural / Q000276:immunology*; D007700:Kinetics; D008213:Lymphocyte Activation; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology*
chemical_list: D000911:Antibodies, Monoclonal; D000954:Antigens, Surface