An increase in the incidence of Sjögren's syndrome in patients with primary biliary cirrhosis has been noted. Indeed, primary biliary cirrhosis has been described as a ductal disease with involvement not only of the biliary tract but of epithelial ductal cells in other organs. We have previously reported the development of a panel of mouse monoclonal antibodies directed at PDC-E2, the major autoantigen of primary biliary cirrhosis. One such antibody, C355.1, but none of the other monoclonal antibodies, reacted not only with mitochondria but also with the apical region of biliary epithelium of patients with primary biliary cirrhosis but not in similar specimens from patients with other liver disease or normal human liver. In addition, we have reported the development of human combinatorial antibodies specific for PDC-E2; these reagents also reacted uniquely with the biliary epithelium of patients with primary biliary cirrhosis. In this paper, we have performed a similar study and have compared the staining of monoclonal antibody C355.1 and a human combinatorial antibody, SP4, with control monoclonal antibodies with respect to their reactivity of salivary glands in 9 patients with primary biliary cirrhosis associated with Sjögren's syndrome, 11 patients with Sjögren's syndrome alone and 7 control patients. Interestingly, the apical region of the salivary gland epithelial cells of approximately 50% of patients with coexisting primary biliary cirrhosis and Sjögren's syndrome had a staining pattern similar to that seen in primary biliary cirrhosis biliary epithelium. In contrast, we did not observe this reactivity in any patient with Sjögren's syndrome alone or in any control patient.(ABSTRACT TRUNCATED AT 250 WORDS)