Competition for receptors for immunoglobulin on cytotoxic lymphocytes.
Target cell killing by lymphocytes can be induced by appropriate antibody complexed to target cell antigens. In this paper it is shown that this form of lymphocyte mediated cytotoxicity is susceptible to inhibition by third party immune complexes which compete with target cell bound antibody for receptors for immunoglobulin on the cytotoxic lymphocytes. The physical state of the complexes is investigated in relation to their inhibitory efficiency. Evidence is presented to show that soluble complexes which exist in antigen–antibody equilibrium or slight antigen excess are the most effective inhibitors. 
 
No evidence could be obtained to support the hypothesis that soluble immune complexes can induce indiscriminate cytotoxic activity in lymphocytes. The biological significance of this effect is discussed in relation to chronic inflammatory diseases.