OBJECTIVETo study the effect of total body irradiation of the donor in a spontaneous tolerance rat liver transplantation model and the role of CD4(+)CD25(+) regulatory T cells on induction of immunotolerance in the recipient.

METHODSLiver transplantation was performed using male Lewis rats as donors and male DA rats as recipients. These rats were randomly allocated into the following groups:Control group, Homogeneity Liver Transplantation group, Idio-immunotolerance group and Acute Rejection group. After transplantation, survival time rate of each group were observed. Serum ALT, TB level, Foxp3(+)CD4(+)CD25(+) regulatory T cells, expression of GITR on T cell subgroup, histopathology of the hepatic graft on day 14, spleen CTL lytic activity on day 14 were measured.

RESULTSIn the Idio-immunotolerance group, the recipients suffered from transient rejection after surgery but acquired immunotolerance and survived long. In the Acute Rejection group, the donors were preconditioned with total body irradiation before liver transplantation. All recipients died between day 17 to 21. Serum ALT and TB increased significantly and the ratio of Foxp3(+)CD4(+)CD25(+) regulatory T cells decreased significantly compared with the Idio-immunotolerance group, the Homogeneity Liver Transplantation group and the Control group. The expression of GITR on CD3(+)CD4(+)T cells in the peripheral blood decreased, the expression of GITR on CD3(+)CD8(+) T cells and CTL lytic activity of the recipients increased by preconditioning of the donors with total body irradiation.

CONCLUSIONSPreconditioning of the donors with total body irradiation eliminated the passenger lymphocytes of the liver graft, decreased the expression of Foxp3(+)CD4(+)CD25(+) regulatory T cells in peripheral blood, and increased the expression of GITR on CD3(+)CD8(+) T cells, thus affected the course of tolerance and induced acute rejection after liver transplantation.