Immunofluorescent studies on S-protein in glomeruli from patients with IgA nephropathy.

Detection of S-protein, which is a regulatory component of the membrane attack complex (MAC), and of C9 in glomeruli by immunofluorescence in 11 of 15 patients with IgA nephropathy is described. The study showed that glomerular injuries such as glomerular adhesion to Bowman's capsule and crescent formation were more marked in glomeruli with S-protein and/or C9 in patients with IgA nephropathy. S-protein co-existed with C9 in glomeruli from such patients. It is suggested that the deposition of S-protein might reflect certain types of histopathologic injuries in glomeruli from patients with IgA nephropathy. It is concluded that activation of terminal components of complement may be one of the exacerbating factors in patients with IgA nephropathy.