Immune abnormalities in IgA nephropathy (Berger's disease)

Abstract

Thirteen patients with IgA nephropathy confirmed by renal biopsies were studied for evidence of disorders of the immune system. Circulating immune complexes (CIC) were determined by agarose gel zone electrophoresis (AGE), the Raji cell radioimmunoassay (RIA), and the modified Raji cell (RIA) for IgA containing CIC. Serum levels of immunoglobulins (Ig) G, A, M, of C3, C4, and properdin factor B (PFB) were measured by the rate nephelometry. Tissue studies included fluorescent, light, and electron microscopy, staining for intracellular Ig, and lysozyme by immunoperoxidase (IP), and determination of glomerular C3 receptors (C3R) by EAC rosettes. IgG-CIC were detected in 69%, IgA-CIC in 50% and serum IgA was elevated (>2SD) in 46% of the patients. In the glomeruli, mesangial deposits of IgA, IgG, properdin, and C3 were present. C3R available for EAC binding to glomerular cells were decreased. IgA-producing lymphoid cells were detected in renal interstitium of our patients especially those with crescentic glomerulonephritis. Elevated serum IgA and the presence of IgA-producing cells in the renal tissue may reflect an abnormality in IgA immunoregulatory mechanisms. IgA could contribute to the pathogenesis of renal disease due to its inhibitory effect on the clearance of circulating and deposited immune complexes.