Clearance and tissue uptake of immune complexes in complement-depleted and control mice

The clearance kinetics, specific hepatic uptake and specific splenic uptake of immune complexes were examined in control mice and in mice treated with large doses of purified cobra venom factor (CoF) to deplete serum C3. At least 90% depletion of C3 was achieved as tested by double diffusion with antiserum specific to antigenic determinants on C3. A saturating dose of preformed immune complexes, consisting of HSA and rabbit antibodies to HSA, was used in these experiments. No differences in clearance kinetics and organ uptake of the immune complexes containing IgG as antibodies were observed between the two groups of mice. Within the limits of the experimental system no evidence was obtained for the participation of serum C3 and C3b receptors on Kupffer cells in the hepatic uptake of circulating immune complexes. The apparent discrepancies on the role of C3 and C3b receptors between these experiments and the in vitro studies on the uptake of immune complexes by macrophages is most likely related to the differences in the lattice of immune complexes employed by investigators.