Expression of HLA-DR antigen on hepatic vascular endothelial cells in idiopathic portal hypertension.

Immunologic abnormalities have been reported in idiopathic portal hypertension, though the exact immunologic mechanism(s) leading to various portal venopathies in this disease remain unsettled. Recently, aberrant expression of HLA-DR antigen on target cells has been noted in the organ-specific autoimmune diseases. In this study the expression of HLA-DR antigen on the hepatic vasculature was surveyed immunohistochemically in idiopathic portal hypertension (n = 36) and in control livers: normal livers (n = 27), chronic active hepatitis (n = 35) and cirrhosis (n = 21). Endothelial cells of hepatic veins and hepatic arteries occasionally expressed HLA-DR antigen, and there was no difference in the expression between idiopathic portal hypertension and controls. Endothelial cells of the main portal vein, within the small and medium-sized portal tract, did not express HLA-DR antigen in idiopathic portal hypertension and controls. By contrast, endothelial cells of the smaller venous radicles, including inlet venules in these portal tracts other than the main portal vein, more frequently expressed HLA-DR antigen in idiopathic portal hypertension (78%) than in chronic active hepatitis (26%), cirrhosis (29%) and normal liver (15%). These data raise the possibility that the smaller venous radicles in the small and medium-sized portal tracts are targets of immunologic attack in idiopathic portal hypertension.