The antibody-dependent cell-mediated cytotoxic reaction. II. The effect of the concentration of anti-target cell antibodies on the identity of the human effector cells.

The circulating leucocytes of normal adults (lymphocytes, monocyte-lymphocyte mixtures and neutrophils) were investigated for their capacity to induce antibody-dependent cell-mediated cytotoxicity (ADCC). The target cell was the rabbit antibody-sensitized chicken erythrocyte. Under conditions of optimal target cell sensitization by anti-target cell antibodies, ADCC cytotoxic activity was exhibited by the neutrophils and lyphocytes to the apparent exclusion of the monocytes. The lymphocytes exhibit activity more rapidly than do the neutrophils and they are more active on an equal cell basis. However, when the effector cells were investigated using target cells sensitized with the anti-target cell antiserum in a threshold concentration, the monocyte and not the lymphocyte or neutrophil displayed ADCC cytotoxic activity. It was concluded that the effector cells in the circulation are heterogeneous and include subclasses of lymphocytes, monocytes and neutrophils and that the identity of the cytotoxic effector cells appears to vary with the concentration of anti-target cell antibodies.