Objective To explore the expression of IFN-γ and IL-10 in lymphocytes in the process of the graft rejection process following liver transplantation in rats and their biological significances.Methods Orthotopic liver transplantation (OLT) models were established by modified Kamada two-cuff technique.Recipients were divided into three groups.The allograft group underwent OLT from male Wistar-to-Sprague-Dawley (SD) rats.The isograft group of SD-to-SD liver transplantation was complemented with a control group of normal male SD rats that had sham operations.The histological changes were examined,as well as serum and Mrna expression levels of IFN-γand IL-10.Results Serious morphological changes were observed in the allografted hepatic tissue.Many necrotic hepatocytes were seen and vacuolar degeneration of kytoplasm,karyopycnosis even nuclear fragmentation was observed in biliary duct endothelial cells.Many inflammatory cells infiltrated the portal areas,and the architecture of the liver lobules was destroyed.In contrast there were mild morphological changes in isograft hepatic tissue .A few inflammatory cells infiltrated the portal area;the hepatic lobule structure remained and biliary duct endothelial cells were nearly normal.Serum IFN-γ levels (pg/ml)determined by ELISA in the allograft group and isograft group were 386.7±14.4 and 159.8±16.5 respectively(P<0.05);for IL-10,they were 126.3±13.1 and 288.3±17.1,respectively(P<0.05).The semiquantitative reverse-transcriptase polymerase chain reaction assay showed that expression levels of IFN-γand IL-10 Mrna were similar to those in serum.Conclusion The expression of IFN-γ was obviously advanced in graft rejection following liver transplantation in rats and the expression of IL-10 was depressed. The dynamic equilibrium of T_H1/T_H2 cytokines is very important in the process of graft rejection following liver transplantation in rats.