Demonstration of immune complexes containing the ribonucleoprotein antigen Ro in primary biliary cirrhosis

We have previously demonstrated circulating and tissue-fixed immune complexes containing the small cytoplasmic ribonucleoprotein antigen Ro and immunoglobulin G (IgG) in a case of sicca syndrome associated with primary biliary cirrhosis. To establish the overall prevalence of such complexes in liver disease, we performed dissociation experiments under conditions of Ro antigen excess. Of the diseases tested, Ro-containing immune complexes were restricted to cases with primary biliary cirrhosis. Sera from 29 of the 47 patients with primary biliary cirrhosis (60%) showed IgG-containing immune complexes; 10 of the 29 sera samples (34%) positive for IgG-containing immune complexes exhibited immune complexes composed of Ro and anti-Ro IgG. These complexes sedimented predominantly as intermediate or large aggregates and were encountered most frequently in cases with extra-hepatic features.