OBJECTIVETo investigate the role of intrahepatic CD4(+)CD25(+) T regulatory cells and Foxp3 gene in the natural tolerance in rat liver transplantation.

METHODSThe orthotopic liver transplantation models of inbred rats (LEW and DA rats) were established with double-sleeve technique and the models were divided into two groups: tolerance group (TOL group, LEW-to-DA) and rejection group (REJ group, DA-to-LEW). The intrahepatic lymphocytes from each group were isolated by using density gradient centrifugation. CD4(+)CD25(+) T cells were isolated by magic cell sorting system (MACS) and identified by flow cytometry (FCM). CD4(+)CD25(+) Tr cells suppression on the proliferation of CD4(+)CD25(-) T effector cells were analyzed by cell proliferation assay in vitro. Western blot was used to detect Scurfin protein expression of CD4(+)CD25(+) Tr cells.

RESULTSCD4(+)CD25(+) Tr cells developed significantly greater in the TOL group than in the REJ group. In vitro, the spleen cells from LEW rats can irritate the proliferation of CD4(+)CD25(+) T cells more obviously than the syngeneic spleen cells. CD4(+)CD25(+) T cells could suppress the proliferation of CD4(+)CD25(-) T cells, but the inhibition was reversed by exogenous IL-2 (200 U/ml).

CONCLUSIONSThe immune suppression function of CD4(+)CD25(+) Tr cell, mediated by Foxp3 gene, is one of the mechanisms in liver transplantation tolerance.