title: Human K cell-mediated haemolysis: determination of the cytotoxic capacity and antibody sensitization requirements of T lymphocyte enriched and depleted populations.
abstract: We have examined the cytotoxic activity of unfractionated peripheral blood lymphocytes (PBL) and T cell-enriched and depleted populations for human red blood cells (HRBC) sensitized with anti-D. Although K cell function was frequently enriched in non-sheep red blood cell (SRBC) rosetting (E-) fractions in some cases cytotoxic activity was equivalent in SRBC rosetting (E+) and non-rosetting cells or greater in E+ populations. The distribution of antibody induced haemolytic activity was similar, but not identical, to that of natural killer (NK) cell-mediated lysis. The sensitization requirements of E- and E+ populations measured as the concentration of anti-D capable of inducing 50% of maximum lysis (Ab50) were similar or identical. In addition it was apparent that the differences in cytolytic potential of E- and E+ are quantitative rather than qualitative since E+ cells exhibited lytic profiles equivalent to E- populations following increase of the effector cell concentration. Despite the similar antibody requirements of E- and E+ effectors these populations exhibited markedly different sensitivity to inhibition of haemolysis by heat-aggregated gammaglobulin (HAG). We conclude that functional K cells are variably distributed between E- and E+ populations and that differences in cytotoxic activity are a reflection of the relative number of effector cells in each fraction. The differences in the sensitivity of E- and E+ K cells to HAG do not influence the apparently identical sensitization requirements of the 2 populations, possibly because receptors for aggregated IgG are independent of those involved in the induction of ADCC.
mesh_terms: D000920:Antibody-Dependent Cell Cytotoxicity; D002469:Cell Separation; D006461:Hemolysis; D006801:Humans; D007114:Immunization; D007136:Immunoglobulins / Q000502:physiology; D007694:Killer Cells, Natural / Q000276:immunology*; D012204:Rh-Hr Blood-Group System / Q000276:immunology; D018029:Rho(D) Immune Globulin; D012397:Rosette Formation; D013601:T-Lymphocytes / Q000145:classification / Q000276:immunology*
chemical_list: D007136:Immunoglobulins; D012204:Rh-Hr Blood-Group System; D018029:Rho(D) Immune Globulin