In vitro uptake and digestion of immune complexes containing guinea-pig IgG1 and IgG2 antibodies by macrophages.

The uptake and digestion of immune complexes by peritoneal macrophages from oil-stimulated guinea-pigs were studied using 125I-labelled guinea-pig IgG1 and IgG2 antibodies to hen ovalbumin. When the IgG1 or IgG2 antibody was incubated with homologous antigen at antigen-antibody ratios ranging from 0-01 to 10, the complexes produced were preferentially taken up by macrophages in the absence of complement and digestion by intracellular enzymes. The uptake and digestion of complexes reached a maximum at an antigen-antibody ratio of 0-1-0-5. In this respect, the IgG1 antibody was indistinguishable from the IgG2 antibody having a cytophilic activity. These observations suggest that some conformational changes in both the IgG1 and IgG2 antibodies or specific molecular arrangement in the lattice work of both the complexes may increase the strength of binding of complexes to macrophages, independently of the difference in biological activities between these two antibodies.