Purified human monocyte subsets as effector cells in antibody-dependent cellular cytotoxicity (ADCC)

Human peripheral blood monocytes are heterogeneous with respect to their size and function. Two monocyte subsets were isolated by countercurrent centrifugal elutriation and were studied with respect to their ability to effect antibody-dependent cellular cytotoxicity (ADCC) and for the presence of Fc receptors on their surface. Both monocyte subsets display Fc surface receptors and are effectors of ADCC against sensitized human erythrocyte target cells. The demonstration of ADCC by monocyte effectors is dependent on their concentration in the incubation mixture. Dilution of monocytes below 10% by unlabeled and unsensitized erythrocytes or lymphocytes significantly suppresses ADCC, presumably by steric inhibition of effector and target contact.