Abstract: ［ABSTRACT］Objective: To study the effect of Astragalus (AST) on CD4+CD25+ T cells and Foxp3 after allotransplantation. Methods: Skin of C57BL／6 mice were transplanted to BALB/c mice. Control group: Sodium Chloride were given, group AST: Astragalus injection were given, group AST+spleen cells (SP): spleen cells of donor mice were given before transplantation and Astragalus injection were given after transplantation, group CsA+SP: spleen cells of donor mice were given before transplantation and Ciclosporin（CsA） were given after transplantation. Survival condition of grafted skin and general condition of mice were observed daily; Numbers of CD4+CD25+ T cells were examined by immunofluorescence staining and flow cytometry; The ｍRNA expression of Foxp3 was tested by RTPCR. Results: Compared with group Control, allograft survival time of group AST、 AST+SP、 CsA+SP prolonged significantly（P＜0.05）, The level of CD4+CD25+ T cells and the expression of Foxp3 ｍRNA increased obviously on 14th day after transplantation（P＜0.05）. Conclusion: Using Astragalus in vivo can prolong graft survival time obviously and upregulate the level of CD4+CD25+ T cells and the expression of Foxp3.

Key words: Astragalus, Allogeneic transplantation, TLymphocytes, Regulatory, Immune tolerance, Mice, Inbred BALB