The influence of antibody sensitization on target cell selection in monocyte-mediated antibody-dependent cellular cytotoxicity.

The role of sensitizing antibody in monocyte-mediated antibody-dependent cellular cytotoxicity (ADCC) has been investigated using human erythrocyte target cells and hyperimmune anti-A and anti-B antisera. The influence of sensitizing antibody concentration on target cell selection by effector monocytes was measured using a cold target competition assay. It was observed that even when red cells were saturated with sensitizing antibody with respect to lytic susceptibility further increases in the density of membrane bound IgG continued to influence their capacity to inhibit lysis in cold target competition assays. It is suggested that although a critical level of sensitization is required for the initiation of lysis, the avidity of interaction between monocyte and target erythrocytes is significantly influenced by further increases in the availability of target-bound antibody.