STUDIES ON CYTOTOXIC ACTIVITY OF HUMAN LYMPHOCYTES .2. INTERACTIONS BETWEEN IGG AND FC RECEPTORS LEADING TO INHIBITION OF K-CELL FUNCTION

Abstract

The inhibition of human K cell-mediated cytolysis by a variety of immunoglobulin [Ig] preparations was studied. Inhibition was not a simple function of IgG concentration but was dependent on the mode of Ig presentation. The relative inhibitory capacity of IgG preparations on a weight basis was as follows: cell associated Ig .gtoreq. immobilized immune complexes > insoluble immune complexes > soluble immune complexes > heat-aggregated Ig .mchgt. monomeric Ig. These results imply that the inhibitory capacity of Ig is determined by ligand (Fc) multivalency. Although interactions between Ig and Fc receptors occur at low temperatures, these interactions lead neither to lysis nor to K cell inactivation. A temperature-sensitive post-binding event was required both for lysis to occur and for K cells to be inactivated. An IgG-induced redistribution (capping) of Fc receptors on the K cell surface may be required for cytolysis and for effector cell inactivation.