A hitherto unknown streptococcal antigen and its probable relation to acute poststreptococcal glomerulonephritis.

In the initial phase of acute poststreptococcal glomerulonephritis (AGN), antigenic sites not covered by specific antibody can be demonstrated in the glomeruli. These sites are on the endothelial side of the glomerular basement membrane and in the mesangial matrix. The antigen is contained in a water-soluble fraction of nephritogenic streptococci.