The effect of immune complex composition on complement activation and complement dependent complex release

The complement activating capacity and complement dependent complex release activity (CRA) of immune complexes (IC) formed at different antigen:antibody ratios were investigated. The correlation between antibody avidity, precipitating capacity and the effect of these parameters on Fcdependent biological functions was studied in BSA-anti-BSA and OA-anti-OA systems. The results suggest that antibody excess favours the complement activating effect of ICs. No correlations between antibody precipitating capacity and avidity was found. However, antibody avidity and complement activating capacity were related: the higher the avidity index of antibodies, the higher the complement activation. The kinetics of CRA are not directly influenced by these characteristics of antibodies. The intercalation of C3b into the lattice interferes not only with the primary antigen—antibody bonds, it may result in the rearrangement of the lattice through the disruption of the non-specific intermolecular interactions.