The localization of glomerular C3b receptor by immunoelectron microscopy.

By an indirect immunoperoxidase technique, rabbit antiserum to solubilized C3b receptor stained the glomeruli in cryostat sections of human kidney. The staining was localized to the glomerular basement membrane zone. Glomeruli in sections of aldehyde-fixed paraffin-embedded tissue did not stain. However, if the sections were pretreated with proteolytic enzymes, the glomeruli were stained by the antiserum as in the cryostat sections. Electron microscopy revealed that the reaction product was located in the cell membrane of the epithelial cells. In some cells the reaction product was also found in vacuoles in the cytoplasm. The basement membrane and endothelial and mesangial cells did not stain.