B7-2 POSITIVE CELLS AROUND INTERLOBULAR BILE-DUCTS IN PRIMARY BILIARY-CIRRHOSIS AND CHRONIC HEPATITIS-C

Bile duct damage in patients with chronic hepatitis C (hepatitis-assoc iated bile duct lesion) as well as that in patients with primary bilia ry cirrhosis (PBC; chronic non-suppurative destructive cholangitis), m ay be causally related to immunological assaults. Efficient antigen pr esentation is known to require the provision of a costimulatory signal which is dependent on the CD28 on T cell surfaces, and that at least two molecules, B7-1 and B7-2, work as costimulatory ligands for CD28. In this study, we examined immunohistochemically, the expression of B7 -2 in portal tracts of liver biopsy specimens obtained from 75 patient s with chronic hepatitis C who had hepatitis-associated bile duct lesi ons, and from 63 PBC patients with chronic non-suppurative destructive cholangitis. B7-2 positive cells were recognizable as large mononucle ar cells scattered in portal tracts. Some of these cells showed a dend ritic cell-like appearance. B7-2 positive cells were observed more fre quently (41%) in PBC liver specimens than in chronic hepatitis C speci mens (17%, P< 0.05). In PBC livers, such cells were preferentially obs erved around the damaged bile duct with a few located in the biliary e pithelial layer. There was no such finding in chronic hepatitis C live rs. The frequency and density of B7-2 positive cells in the liver spec imens tended to decrease according to the stage of PBC (45% in stages 1 and 2, and 33% in stages 3 and 4; P=0.10), whereas with chronic hepa titis C, no such tendency was observed. These findings suggest that B7 -2 positive cells may play a role in the bile duct lesions that appear in the early histological stages of PBC and that the immunological me chanisms of bile duct damage, particularly of antigen presentation and B7-2 expression, differ between PBC and chronic hepatitis C.