The pathogenesis of graft-versus-host reaction in the intrahepatic bile duct. An immunohistochemical study

Although intrahepatic bile duct injury following bone marrow transplantation is considered to be one feature of graft-versus-host disease, its developmental mechanism has not been clarified. In order to elucidate this aspect, an immunohistochemical study of the liver following human allogeneic bone marrow transplantation was made. Cytotoxic T lymphocytes (Tc) and natural killer cells (NK) were found in contact with intrahepatic bile duct epithelial cells showing degeneration and necrotic changes. These findings suggested a cytotoxic effect of these cells on bile duct epithelial cells. Abnormal expression of HLA class II (DR) antigen was recognized in intrahepatic bile duct epithelial cells following bone marrow transplantation. Cell injury was prominent in cells with weak DR antigen expression, whereas the cells demonstrating conspicuous expression appeared almost normal. There results suggest that abnormal expression of DR antigen plays an important role in the development of GVHD of the intrahepatic bile duct.