The antibody-dependent cell-mediated cytotoxic (ADCC) reaction. III. Lymphocyte, neutrophil and monocyte cytotoxic activity as a function of the alloantibodies and erythrocyte target cells in the human allogeneic ADCC assay.

The sera of a number of individuals containing anti-A and anti-B antibodies were investigated for their ability to sensitize group AB, Rh positive erythrocytes to lysis by allogeneic circulating cells in the allogeneic ADCC assay. There was no correlation between the hemagglutination titer and the capacity to mediate ADCC lysis. Only IgG, and not IgM, alloantibodies could mediate this cytotoxic activity. A number of the alloantisera facilitated cytotoxic activity by lymphocytes whereas other alloantisera facilitated lysis by monocytes and not lymphocytes. All of the alloantisera tested sensitized the target erythrocytes to lysis by neutrophils. It is concluded that one cannot predict whether the lymphocyte or the monocyte will be the cytotoxic mononuclear cell in the human allogeneic ADCC assay since the alloantibodies, apparently directed toward the presumed identical surface structures on the identical target cells, can nevertheless preferentially impart cytotoxic activity to either of these 2 cells. The mechanism whereby the antibodies determine whether lymphocytes or monocytes will be the cytotoxic cells can only be conjectured upon at the present time.