Heterogeneity among human lymphocyte effector cells mediating spontaneous lymphocyte-mediated cytotoxicity

The spontaneous lymphocyte-mediated cytotoxicity (SLMC) of lymphocytes from normal individuals was studied using the lymphocyte titration assay. Various techniques were used to study selectively several lymphocyte subpopulations. The activity of these subpopulations was tested in both the antibody-dependent cellular cytotoxicity (ADCC) and lymphocyte titration assays. Surface marker studies were performed on each lymphocyte subpopulation. The results from these studies indicate that effector cells mediating SLMC are a heterogeneous lymphocyte population composed of Fc-receptor-positive lymphocytes both with and without C3 receptors that consistently segregate with cells that do not form rosettes with sheep red blood cells. Our data suggest that, in many respects, the effector cells in SLMC and ADCC are identical. However, the mechanism appears to be different.