Removal of glomerular deposits of immune complexes in mice by administration of excess antigen

We have previously shown that the deposition of preformed immune complexes in glomeruli depends on the presence of large latticed complexes (>Ag₂Ab₂) in the circulation. In this study we report the complete disappearance of extracellular glomerular deposits of immune complexes from the subendothelial and mesangial regions by administration of excess antigen. Glomerular deposits of immune complexes were produced by giving unimmunized mice soluble immune complexes prepared with human serum albumin and reduced and alkylated or intact rabbit antibodies to human serum albumin. Varying doses of excess human serum albumin were administered; 12 hours later immune complexes were no longer detectable in glomeruli by immunofluorescence microscopy with antibodies to rabbit IgG or with antibodies to human serum albumin. By electron microscopy no electron-dense deposits were found in the glomeruli. When the excess antigen was administered at longer intervals after the injection of immune complexes, the extracellular deposits disappeared, but the complexes that had been ingested by phagocytic cells remained in glomeruli. These studies show that the subendothelial and mesangial regions of the glomerulus are readily accessible to circulating antigen. The excess antigen in circulation leads to release of complexes deposited in glomeruli, presumably by conversion of large latticed complexes to small latticed complexes in vivo.