To explore the role of type 1 regulatory T (Tr1) cells in allogeneic bone marrow transplantation (allo-BMT), we generated Tr1 cells from naive CD4(+) T cells in donor mice that were subjected to stimulation of recipient interleukin (IL)-10 gene-modified dendritic cells (DCs). In animal models, the severity of graft-versus-host disease (GVHD) in the group co-infused with DC-induced Tr1 cells was markedly milder than that in the groups without infusion of Tr1 cells. Moreover, the co-infusion Tr1 cells significantly prolonged the leukemia-free survival in tumor-bearing mice. Besides, Tr1-induced cells mediated the shift from T helper (Th)1 to Th2 cytokines in allo-BMT recipients. In Conclusions, our findings suggest that IL-10 gene-modified DC-induced Tr1 cells could inhibit GVHD while maintaining Graft-versus-leukemia (GVL) through mediating the shift of Th1/Th2 cytokines in an allo-BMT mice model. (C) 2018 Published by Elsevier Inc.