The effect of complement-depletion or mannosyl receptor blockade on the in vivo clearance of antigen during a primary immune response in rabbits.

The effect of complement-depletion mediated by cobra venom factor or mannosyl receptor blockade induced by ovalbumin injections on the blood clearance of in vivo-generated soluble immune complexes were analysed in 2 variants of a primary immune elimination model system in rabbits. In the first variant, animals were immunized with particulate antigen to elicit high titre IgM antibodies, and received radiolabelled antigen on the first day of immunization. In the second variant, radiolabelled antigen was introduced on Day 8 of the immunization schedule. The results showed that (a) immune clearance of antigen (Days 6-8) was not inhibited by prior decomplementation of the animals with cobra venom factor, and (b) injection of ovalbumin just prior to immune clearance did not significantly alter the clearance kinetics of the resulting immune complexes. Thus, the results indicate that clearance of soluble immune complexes generated during a primary immune response is not mediated via C3b-C3b receptor interaction or via mannosyl-mannosyl receptor interaction in the reticuloendothelial system, but proceeds through other mechanisms perhaps involving Fc receptors.