Immunopathological study on the development of swine serum-induced bile duct lesions in BALB/c and DBA/2 mice

To compare the difference in the development of swine serum (SS)-induced bile duct lesion (BDL) between high responder BALB/c and low responder DBA/2 mice, the mice of both strains injected with SS twice a week for up to 4 weeks were killed and examined immunopathologically after the 2nd, 4th, 6th and 8th SS-injection, respectively. In BALB/c mice, BDL developed rapidly following the SS-injections, and a slight enlargement of common bile ducts accompanied with infiltration of T helper cells and eosinophils was detected after the 2nd SS-injection. From the 4th injection on, BDL was characterized by proliferation of mucous glands, hyperplasia and hypertrophy of biliary and glandular epithelial cells, periductal fibrosis, infiltration of eosinophils, plasma cells and T helper cells, and increase of mast cells, resulting in more apparent enlargement of common bile ducts. Several hypertrophied biliary and glandular epithelial cells were positive for mouse immunoglobulins and SS. BDL subsided after cessation of the SS-treatment. On the other hand, in DBA/2 mice, immune response and inflammatory reaction were very weak, and only slight BDL were detected.