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The immunofluorescent localization of antisera to human glomerular basement membrane (GBM), collagen, and smooth muscle actomyosin was examined in 15 specimens of normal renal tissue and 98 specimens from patients with renal disease. The anti-GBM and anticollagen antisera normally localize to GBM, while antiactomyosin localizes to the mesangium. Diabetic nephropathy revealed a striking expansion of mesangial material reacting with antiactomyosin. In contrast, the expanded mesangium in membranoproliferative glomerulonephritis did not react with antiactomyosin, and the GBM localization of anti-GBM and anticollagen sera was similarly lost. The thickened GBM in diabetes mellitus and membranous nephropathy reacted with anti-GBM and anticollagen, but with accentuation of staining on the inner aspect of the GBM. In proliferative glomerulonephritis there was a moderate increase in the distribution of actomyosin. Glomerular sclerosis and hyalinization in all diseases studied was accompanied by a loss of immunofluorescent staining for all glomerular antigens, including collagen.

After being injected with collagen from rat or guinea pig skin, rabbits form high titer, species-specific antibodies to collagen. Antibody is directed primarily against the alpha2 chain of collagen with little reaction with the alpha1 chain. The amino terminal peptide of cyanogen bromide cleavage of the alpha2 chain of guinea pig skin collagen, alpha2-CBl, effectively inhibited the antigen-antibody reaction, an indication that a major antigenic determinant of collagen is located at the amino terminal of the alpha2 chain.