IgA-associated glomerular deposits in liver disease.

IgA-associated immunopathologic renal injury has been reported in patients with cirrhosis. In an effort to elucidate the pathogenesis of this phenomenon, the livers and kidneys obtained at autopsy from a group of patients with cystic fibrosis were studied; these patients were selected because of their broad spectrum of liver abnormalities. On the basis of histologic examination of sections of liver, the patients were divided into two groups: Group I (20 patients) included patients with focal biliary cirrhosis and multilobular biliary cirrhosis; all had anatomic distortion of the biliary system, and many had cholestasis. Group II (28 patients) showed no bile duct anomalies. Immunofluorescence studies of the corresponding kidneys for immunoglobulin, complement, and free secretory component (FSC) revealed significantly more numerous IgA-containing glomerular deposits in group I (P less than 0.02). Although FSC was virtually absent in these deposits, significant in vitro binding of this protein revealed the polymeric nature of the glomerular IgA. This is consistent with previous observations of elevated serum levels of polymeric IgA, which forms the dominant component of glomerular deposits in cirrhotic patients. Since IgA glomerular deposition occurred in patients with focal biliary and no hepatocellular dysfunction, it seems that the source of this polymeric IgA is related to its impaired serum clearance by a distorted and stagnant bile duct system. However, the mechanism that leads to the deposition of this immunoglobulin in the glomeruli and other tissues remains conjectural.