MUC1
apomucin is a specific target
tumor antigen recognized by cytotoxic T cells in a major histocompatibility complex (MHC) unrestricted fashion in patients with pancreatic and
breast cancer. This T-cell-mediated immune mechanism against MUC1
apomucin expressing cells has not been evaluated in nonneoplastic immune-mediated diseases. Therefore, we immunohistochemically surveyed the expression of MUC1
apomucin on biliary epithelial cells of small bile ducts in various
hepatobiliary diseases, including
primary biliary cirrhosis (PBC). MUC1
apomucin was detected using the
monoclonal antibody DF3 and the
streptavidin-
biotin complex, in livers from 31 patients with PBC, 67 with chronic viral
hepatitis (CH) with or without
cirrhosis, 31 with extrahepatic biliary obstruction (EBO), 30 with hepatolithiasis, and from 23 normal individuals. MUC1
apomucin was infrequently and focally expressed in the biliary epithelial cells of the small bile ducts in 3 of 23 normal livers. In contrast, MUC1
apomucin was frequently and strongly expressed on the
luminal surface of biliary epithelia] cells of small bile duct, in 22 of 31 patients with PBC, and in 50 of 67 patients with CH. In particular, high levels of MUC1
apomucin were expressed in bile ducts showing chronic nonsuppurative destructive
cholangitis (CNSDC) in PBC and hepatitic duct
injuries in CH. In EBO and hepatolithiasis, MUC1
apomucin was focally and weakly expressed in 29% and 30% of livers examined, respectively. More MUC1
apomucin was expressed in PBC and CH than in EBO, hepatolithiasis, and normal liver (P < .01, respectively). Frequent and high
luminal expression of MUC1
apomucin on biliary epithelial cells in damaged small bile ducts in PBC and CH may be related to T-cell-mediated immunologic mechanisms in these diseases, probably by an MHC-unrestricted recognition process.