Leflunomide Prolonged Concordant Cardiac Xenograft Survival By Inhibiting T Cells

Background:The mechanism of leflunomide in concordant xenotransplantation was studied in a rat to mouse xenograft model.Materials and methods:SPF-grade and cleaner-grade Lewis/SD rats were used as donors,and C57BL/6 or Balb/c mice were used as recipients for cervical heterotopic heart transplantation to observe their survival.Then,SD rats and C57BL/6 mice were used as donors and recipients for cervical ectopic heart transplantation.Recipients mice were divided into two groups:the control group was not treated with anti-rejection drugs,and the experimental group was treated with leflunomide monotherapy(30mg/Kg·d).The survival period of the two groups was observed,and graft,recipient serum and spleen cells were collected on the 6th day after surgery for detection.Finally,Balb/c mice were used as the donor and C57BL/6 mice were used as the recipient for the allotransplantation.The mice were divided into two groups:the control group was not treated with anti-rejection drugs,and the experimental group was treated with leflunomide monotherapy(30mg/Kg-d).The survival period of the two groups was observed,and graft,recipient serum and recipient spleen cells were collected on the 6th day after surgery for detection.Results:In different donor and recipient combinations,SPF grade and clean grade SD rat donors were transplanted into Balb/c mice,and the survival time of SPF grade rat grafts was better than that of clean grade rat grafts(5.4±0.20d vs 1.0±0.00d,p<0.001).There was no significant difference in the rest of the survival time,while the H&E pathological examination of the clean grade rat donor heart showed hyperacute rejection.In the xenotransplantation of C57BL/6 mice,the survival time of the experimental group was better than that of the control group(34.0 ± 3.10d vs 11.5±0.60d,p<0.001).The proliferation of spleen lymphocytes in the experimental group was lower than that in the control group.The number of CD4+and CD8+T cells in the spleen of the experimental group was inhibited.Serum IgG and IgM levels in the experimental group decreased.The expression of IL-2,INF-y and Foxp3 related genes in the grafts of the experimental group increased,while the expression of IL-4 related genes decreased.In the spleen of the allograft recipient,the number of CD4+and CD8+ T cells in the spleen of the experimental group was inhibited,the expression of IL-2 and INF-? related genes in the graft of the experimental group was decreased,while the expression of IL-4 and Foxp3 related genes was not significantly changed.Conclusions:Hyperacute rejection of grafts can be induced in a concordant xenograft model in Balb/c mouse xenografts from clean-grade offspring rats,and this is due to the donor's feeding cleanliness level,not the rat strain.Leflunomide in rat pups to C57BL/6 mice heart xenotransplantation model,can effectively extend the graft survival time,the effect is through the form in graft "Foxp3+regulatory T cells inhibit Th1 ways to activate cell mediated rejection but does not affect the function of the secretion of cytokines,Th1 ways through the secretion of IL-2 and INF-y factor inhibiting Th2 activation of acute vascular rejection" such a serial suppression system implementation.Compared with the heart allotransplantation model from Balb/c to C57BL/6 mice,leflunomide only suppressed the Th1 pathway to achieve anti-rejection effect.