Carbonic anhydrase II (CA-II), an enzyme that catalyzes hydration of carbon dioxide to bicarbonate and hydrogen ions, is located exclusively in cholangiocytes in the liver. Recently, patients with autoimmune cholangitis have been reported to have serum antibodies to CA-II. Moreover, active immunization of susceptible mice with CA-II results in inflammation of submandibular glands, where CA-II is also expressed. In the present study, we attempted to produce cholangitis by immunization with CA-II using two strains of mice with different potential susceptibilities. Balb/c and DBA/1J mice were immunized with a dose of human CA-II (100 microg) intraperitoneally every other week on three occasions. One week after the final immunization, mice were killed and blood and tissue samples harvested. Light and electron microscopic evaluation for inflammation was performed under coded identification. After immunization of Balb/c mice, numerous mononuclear cells, mostly CD4-positive T cells, appeared around bile ducts; lymphocyte invasion between cholangiocytes was also seen. Inflammation was not observed outside the liver. Morphologic evidence of cholangitis was observed in 8 (53.3%) of 15 Balb/c mice and in 3 (20%) of 15 DBA/1 J mice. In the control mice immunized with bovine serum albumin (BSA), cholangitis was observed in only 1 (6.7%) of 15 Balb/c mice and none of 15 DBA/1J mice. Balb/c mice immunized with CA-II had statistically significant cholangitis compared with those immunized with BSA (p < 0.01), whereas DBA/1J did not show a significant difference from controls. Balb/c mice immunized with CA-II showed specific antibody production after immunization, whereas DBA/1J mice immunized with CA-II had anti-CA-II antibody even in preimmune sera. Adoptive transfer of splenocytes from CA-II-immunized Balb/c mice resulted in cholangitis in two (66.7%) of three Balb/c recipients. These data strongly suggest that the cholangitis can be induced by CA-II immunization in susceptible strains of mice.