Expression of beta 2-microglobulin on interlobular bile ducts in primary biliary cirrhosis and other hepatobiliary diseases.

Expression of beta 2-microglobulin, a reliable marker of HLA Class I, on the interlobular bile ducts (bile ducts) was surveyed using an immunoperoxidase method in paraffin sections of specimens from patients with a variety of hepatobiliary diseases. Normal bile ducts showed negativity or weak cytoplasmic positivity in normal as well as diseased livers. On the other hand, abnormal bile ducts showing degenerative or proliferative changes in primary biliary cirrhosis and graft-versus-host disease revealed enhanced expression of this protein, suggesting that these damaged bile ducts might be more susceptible to T cell-mediated immune attack in these immunologic diseases. However, enhanced expression of this protein was also similarly found on abnormal bile ducts in several nonimmunologic biliary diseases including extrahepatic biliary obstruction. Enhanced expression of this protein on the interlobular bile ducts may therefore be an epiphenomenon secondary to different primary pathologic events in the biliary tree, such as immunologic and nonimmunologic processes.