Modulation of C2 biosynthesis by antigen-antibody complexes.

Antigen-antibody complexes prepared with BSA and immunoadsorbent purified anti-BSA enhance C2 production by human monocytes in culture. The ratio of antigen to antibody was found to influence the degree of enhancement of C2 synthesis. Complexes prepared with F(ab)2 had no effect on C2 synthesis, suggesting that the effect was mediated via the Fc receptor. Enhanced C2 production by antigen-antibody complexes was reversibly inhibited by cycloheximide (2.5 micrograms/ml). In contrast to complexes heat-aggregated rabbit IgG inhibited C2 production. The biological relevance of these findings is discussed.