Antibody-dependent cell-mediated cytotoxicity: heterogeneity of effector cells in human peripheral blood

We have compared antibody-dependent cell-mediated cytotoxicity (ADCMC) of human peripheral blood leukocytes (PBL) in three model systems. target cells were 51Cr-labeled mouse mastocytoma cells, chicken erythrocytes (CRBC), and human erythrocytes (HRBC) coated with appropriate heterologous or isologous antisera. Effector cells were characterized on the basis of their adherence, phagocytosis, radiosensitivity, and sedimentation velocity(s) at 1 g. In predominantly mononuclear (Ficoll-Isopaque-purified) PBL preparations (MPBL) HRBC were lysed by an adherent, phagocytic population of cells that was markedly radio-resistant. Sedimentation velocity analysis further established that these effector cells were restricted to rapidly sedimenting fractions (s greater than 4.5 mm/hr). On the other hand, mastocytoma cells were lysed by a population of MPBL that was nonadherent, nonphagocytic, and relatively radiosensitive. These cells mainly restricted to slowly sedimenting fractions (s greater than 4.5 mm/hr) following 1 g velocity sedimentation. CRBC appeared to be susceptible to lysis by both types of mononuclear effector cell. In some experiments, enriched populations of polymorphonuclear leukocytes (PMN) were isolated. These cells were found to lyse both HRBC and CRBC very efficiently, whereas mastocytoma cells were lysed very little if at all by the same effector populations. Taken together, these results suggest that antibody-coated mastocytoma cells are lysed uniquely by effector cells in human peripheral blood with the physical properties of lymphocytes, whereas antibody-coated HRBC are lysed by both monocytes and PMN, but not by lymphocytes. Antibody-coated CRBC would appear to be lysed by all of the three effector cell types tested.