Immunohistochemical localization of IgA and secretory component in rat liver.

IgA is transported from rat blood into bile. The localization of IgA and secretory component in rat liver was studied in order to facilitate understanding of this IgA transport. Both indirect immunofluorescence and unlabeled antibody enzyme histochemical techniques were used. Immunoglobulin A was found surrounding bile canaliculi, within bile duct epithelium, on or near the plasma membranes of hepatocytes, within the cytoplasm of a few intensely stained hepatocytes, within the cytoplasm of intensely reactive cells found in or adjacent to the sinusoids, and in sparsely distributed plasma cells. Reactivity for secretory component was present surrounding bile canaliculi, within bile duct epithelium, or or near the plasma membranes of hepatocytes and in the cytoplasm of hepatocytes. These findings are compatible with the hypothesis that immunoglobulin A is transported from blood to bile through hepatocytes by a process involving secretory component. Bile duct epithelium may also have a role in immunoglobulin A transport.