ANALYSIS OF CELL-SURFACE ANTIGENS USING ANTI-RAT HEPATOCYTE MONOCLONAL-ANTIBODIES, PARTICULARLY HAM-1

The expression of antigens on rat hepatocytes was examined by immunoel ectron microscopy using monoclonal antibody HAM 1. The antigen recogni zed by HAM 1 was expressed mainly on both sinusoidal and bile-canalicu lar faces and only sparsely on the contiguous face. All rat hepatoma c ell lines examined were intensely labeled with HAM 1, but poorly label ed with HAM 3, HAM 4, and HAM 5, as revealed by flow cytofluorometry a nd radioimmunoassay. Expression levels of HAM 1 antigen on the AH 44 h epatoma cell line similar to the degree seen in normal liver were demo nstrated by radioimmunoassay. HAM 1 antigen was also expressed weakly on lymphocytes, thymocytes, and some bone marrow cells, but not on red blood cells, and differed from the MHC class I antigen recognized by HAM 2 and OX 18. Significant amounts of cell surface antigens recogniz ed by all the monoclonal antibodies (HAM 1-HAM 5) were confirmed by ra dioimmunoassay on the cell surface of primary cultured hepatocytes. Th ese results suggest that the rat hepatoma cell lines employed are diff erent from normal hepatocytes, that primary cultured hepatocytes are m ore similar to normal hepatocytes in the degree of expression of their cell surface antigens, and that HAM 1 antigen appears to be a signifi cant antigen on both normal and transformed hepatocytes. (C) 1994 Acad emic Press, Inc.