Increased expression of major histocompatibility antigens in the liver as a result of cholestasis.

Increased expression of major histocompatibility complex (MHC) antigens may occur following liver transplantation. The mechanism by which this occurs is unclear. Postoperative complications may result in cholestasis. We have investigated the possibility that cholestasis may cause increased expression of MHC antigens in the liver. Cholestasis was induced in rat livers by bile duct ligation and transection. Total serum bilirubin rose markedly postoperatively and remained elevated over a period of 21 days. Samples of bile taken from rats were shown to remain sterile during the study period and there was no evidence of viral infection. Liver tissue taken 1, 3, 7, and 21 days postobstruction showed a marked increase in the expression of rat class I MHC antigens but not class II antigens. We suggest that cholestasis itself can induce increased MHC class I antigens in the liver. Therefore, if cholestasis occurs postoperatively in the human liver transplant recipient this might lead to increased expression of human class I MHC antigens and add to the overall cellular immune activity in a rejection reaction, although cholestasis probably cannot initiate rejection.