Purification and characterization of human nephritogenic antigen that induces anti-GBM nephritis in rats.

Human nephritogenic antigen induces anti-glomerular basement membrane antibody glomerulonephritis in rats. This antigen was purified from collagenase-solubilized renal basement membrane by means of gel filtration and affinity chromatography using a rabbit antibody. Western blots of the purified nephritogenic antigen using epitope-defined monoclonal antibodies showed that it contains the NC1 domains of the a1 to a6 chains of type IV collagen. Nephritogenicity was thought to be a feature of the NC1 domains of the a3 to a5 chains, because the a6 chain is not located in the glomerular basement membrane, and because an NC1 fraction consisting of the NC1 domains of the a1 and a2 chains was poorly nephritogenic. Autoantibodies in the sera of patients with Goodpasture's syndrome were detected by ELISA using the purified nephritogenic antigen. These results indicate that the nephritogenic antigen contains the Goodpasture antigen, defined as the antigen reactive with sera from patients with Goodpasture's syndrome.