Localization of the receptors for activated complement on the visceral epithelial cells by the human renal glomerulus by immunoenzymatic microscopy.

Horseradish peroxidase-labeled IgG-anti-IgG immune complexes bearing activated third component of complement, C3, were used as indicator particles for the localization of the complement receptor in the human renal glomerulus. The HRP-labeled IgG-anti-IgG complexes were coated with activated C3 by exposing them to fresh human serum as a source of complement. This represents a more physiologic indicator particle for complement receptor-bearing structures than the synthetic immune complexes previously used. By light microscopy, the deposition of the complexes was restricted to the glomeruli. By transmission electron microscopy, the complexes were selectively associated with the surface of the visceral epithelial cells (podocytes). Complexes exposed to buffer alone or to heat-inactivated human serum failed to adhere to any of the renal structures examined.