A human NK and K cell subset shares with cytotoxic T cells expression of the antigen recognized by antibody OKT8.
The antigen recognized by monoclonal antibody OKT8 is expressed on the cell membrane of 30 to 50% of human NK/K cells. The reactivity of OKT8 with NK/K cells was determined by indirect methods (treatment of the effector cells with OKT8 antibody and complement (C) and separation of OKT8(+) and (-) effector cell populations by fluorescence-activated cell sorting or by rosetting techniques) and, at single cell level, by C-dependent lysis of effector NK cells that bind and kill K562 targets. Analysis by indirect immunofluorescence (flow cytofluorometry) of lymphocyte subpopulations mediating NK/K cytotoxic activity and deprived of OKT8(+) T cells reveals that the NK/K cell subset bears OKT8 antigen at a density lower than that present on cytotoxic T cells. The OKT8 antigen on NK/K cells is trypsin- and pronase-sensitive, but it is resynthesized by the same effector cells during 24 hr of culture at 37 degrees C. OKT8 antibody does not inhibit NK killing, and, on a per cell basis, OKT8(+) cells within the NK/K subset mediate the same level of cytotoxic activity as OKT8(-) NK/K cells. Analogous results were obtained by using anti-Leu-2a, an antibody with the same specificity as OKT8 on cytotoxic/suppressor T cells, but not when OKT5 was used, which might identify a distinct epitope on the same antigenic molecule. The possible significance of these findings in understanding the cell lineage of NK/K cells is discussed.
D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology* / Q000502:physiology; D000945:Antigens, Differentiation, T-Lymphocyte; D000954:Antigens, Surface / Q000032:analysis / Q000276:immunology; D002469:Cell Separation; D003601:Cytotoxicity Tests, Immunologic; D005434:Flow Cytometry; D005455:Fluorescent Antibody Technique; D006801:Humans; D007694:Killer Cells, Natural / Q000276:immunology*; D051379:Mice; D010447:Peptide Hydrolases / Q000494:pharmacology; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology*
D000911:Antibodies, Monoclonal; D000945:Antigens, Differentiation, T-Lymphocyte; D000954:Antigens, Surface; D010447:Peptide Hydrolases