Expression of the major histocompatibility complex antigens on different liver cellular components in rat and man

We have analysed the distribution of the major histocompatibility complex (MHC) antigens on different liver cellular components in rat and man. Two types of antisera were used: monospecific rabbit antisera raised against isolated molecules of class I and class II and ordinary hyperimmune alloantisera directed to their allelic specificities. A modified Staphylococcus aureus rosette test, enabling morphological identification of the rosette-forming cell type, was used. In both species the passenger cells, especially the Kupffer cells reacted strongly with rabbit anti-class I and II. The passenger erythrocytes reacted with anti-class I in rat but not in man. Human liver vascular endothelial and bile duct cells displayed a distinct reaction with anti-class I and II, whereas the hepatocytes reacted only very weakly, if at all. In rat liver parenchymal component the expression of these antigens was different and weaker. Rat bile duct cells reacted with anti-class I and II in approximately 50% of the testings, whereas rat vascular endothelial cells and rat hepatocytes were essentially non-reactive. The alloantiserum reactivity (tested only in the rat) followed closely that of heterologous antisera, and the reactivity of anti-beta 2m that of class I alloantisera. Although these differences are probably quantitative rather than qualitative, the results suggest considerable variation in the expression of ther MHC antigens on different liver cellular components. These differences partially explain why liver allografts behave differently than, e.g., renal allografts upon transplantation.