Abstract： Objective To investigate the effect of donor lymphocyte infusion(DU) by intra-bone marrow(IBM)or intravenous(Ⅳ)on the incidence of graft-versus-host disease(GVHD)and graft-versus-leukemia(GVL)after allogeneic peripheral hematopoietic stem cen transplantation(allo-PBSCT).Methods Female C57BL/6 mice as recipients received total body irradiation (TSr) Oil day 0,followed by injection of peripheral hematopoietic stem cells from mobilized male BALB/e with the granulocyte-colony stimulating factor(rhG-CSF),and DLI Was performed via Ⅳ or IBM.The extents of GVHD and GVL were compared in recipients received IBM-DLI with those received IV-DLI.The percentages of donor-defived cells and CD_4~+ CD_(25)~+ regulatory T cells(Treg) were detected by flow cytometry.Results It Was found that the frequency of GVHD and GVL were reduced in IBM-DLI compared with that of IV-DLI(P<O.01);the percentage of H-2~d antigen positive cells wag over 95% in all surviving transplanted mice 7 days after transplantation;and the percentage of Treg detected as CD_4~+ CD_(25)~+ was significantly higher that in recipients treated with IBM-DLI than that in those treated with IV-DLI(P<0.011 14 days after transplantation.Conclusion IBM-DLI could induce the proliferation of Tregs,resulting in alleviating the incidence of GVHD,while preserve the GVL effect.