Expression of adhesion molecules and human leukocyte antigens on the surface of hepatocytes (HC) may play an important role in the immune reaction in different types of infectious and noninfectious hepatitis, liver graft rejection, and autoimmune liver diseases. The aim of this study was to evaluate the influence of the proinflammatory cytokines IFN-alpha, IFN-gamma, and IL-1 alpha on the expression of intercellular adhesion molecule-1 (ICAM-1) and HLA-A, -B, -C, and -DR on highly purified primary human HC in cell culture. Expression was assessed by semiquantitative measurement of HC in cell culture by means of computer-aided fluorometry after immunofluorescent labeling. Avidin-biotin-immunoperoxidase staining was applied on parallel cultures to evaluate cell purity (> 99%) and to confirm the results obtained by fluorometry. ICAM-1 was expressed constitutively on untreated HC in vitro. Stimulation of HC with IFN-gamma and IL-1 alpha for 24 hr resulted in an increase of ICAM-1 expression. Cultured HC were moderately HLA-A, -B, and -C positive, but HLA-DR negative. Stimulation of HC with 500 U/ml IFN-gamma for 72 hr resulted in an increase of HLA-A, -B, -C, and -DR expression, whereas stimulation with 10 U/ml IL-1 alpha for 72 hr had no influence. By using 5000 U/ml IFN-alpha for 72 hr, we achieved an increase of HLA-A, -B, and -C expression; effects on the other tested antigens were not significant. In contrast to endothelial cells and transformed human hepatocytic cell lines, ICAM-1 on HC was changed more intensively by IFN-gamma than by IL-1 alpha. Furthermore, the results reveal differences in HLA and ICAM-1 expression between HC in vivo and in vitro.