Antibody-dependent cell cytoxicity (ADCC). Characterization of 'killer' cells in human lymphoid organs.

The effector cell(s) in human antibody-dependent cell cytotoxicity (ADCC), with antibody-coated chickens erythrocytes as targets, was studied by comparison of cell suspensions from various lymphoid organs and by means of various cell fractionation methods. Effector cells (K) were found mostly in peripheral blood, spleen, and bone marrow but not in tonsils, lymph nodes, and thymus. Effector cells bear Fc receptors and can form EA rosettes with the antibody-coated target cells. About 1,5% peripheral blood lymphocytes can form 'high-avidity' EA rosettes with targets coated at low antiserum concentration. Most of the effector cells belong to this small subset, as shown by experiments of selective depletion. Removal of most monocytes, T cells, or B cells from, or addition of T-cell-specific antiserum to, the effector cell suspensions did not affect ADCC. Effector cells in this model of ADCC therefore lack the conventional B- or T-cell markers but at least some of them are likely to bear C3 receptors.