Secretory component and immunoglobulins in the intrahepatic biliary tree and peribiliary gland in normal livers and hepatolithiasis.

Distribution of secretory component (SC), IgA, IgM and joining chain (J chain) in the intrahepatic biliary epithelium and peribiliary glandular epithelium were studied in normal livers and hepatolithiasis. In normal livers, SC was immunohistochemically demonstrated homogeneously in the cytoplasm of the biliary lining and peribiliary glandular epithelium. Immunoelectron-microscopically, SC was localized in the basolateral plasma membranes, nuclear membranes, rough endoplasmic reticulums, Golgi complexes and intracytoplasmic small vesicles, suggesting that the biliary lining and peribiliary glandular epithelium has an ability to synthesize SC. On the other hand, IgA and IgM were found heterogeneously in the biliary lining epithelium, and immunoelectron-microscopically they were only localized in the basolateral plasma membranes and vesicles. J chain was found in similar portions, suggesting that IgA and IgM in biliary lining and glandular epithelium were polymeric. It seems likely that polymeric IgA and IgM combine with SC on the biliary lining and glandular epithelial membranes, and subsequent endocytic transport and secretion of these complexes into the bile occur. In hepatolithiasis in which biliary living epithelia are hyperplastic and peribiliary glands proliferate markedly, such endocytic transport and secretion seemed to be increased. From these findings, it was suggested that the peribiliary glandular as well as biliary lining epithelium contributes to a local immunity in the biliary tree, especially in hepatolithiasis.