Comparison of monocyte and alveolar macrophage antibody-dependent cellular cytotoxicity and Fc-receptor activity.

The cytotoxic potential of rabbit peripheral blood monocytes and alveolar macrophages in antibody-dependent cellular cytotoxicity (ADCC) toward both erytbrocyte (RB&) and tumor cell (CEM T-lymphoblast) targets was examined. ADCC was measured in a 4-hr “Crrelease assay. Alveolar macrophages were more efficient at killing the tumor cell targets (optimally sensitized with rabbit antisera) than monocytes at similar effector cell/target cell (E/T) ratios. Tumor cell targets sensitized with seven different antisera (anti-CEM) were lysed by alveolar macrophages but not by the monocytes. In marked contrast, the monocytes were more effective at lysing the sensitized erythrocyte target cells. The degree of cytolysis of RBCox and CEM was dependent on the E/T ratio and the degree of sensitization of these target cells. It was demonstrated that the effector cell selectivity in ADCC was directly related to their ability or inability to bind the sensitized target cells as determined by Fc-receptor rosette formation. The transition from monocyte to macrophage may, therefore, have resulted in an alteration in the criteria necessary for Fc-receptor binding to antibody-sensitized target cells and subsequent ADCC.