Background AIIogeneic transplant rejection is currently a major problem encountered during organ transplantation.The dendritic cell (DC) is the most effective powerful known professional antigen-presenting cell,and recent studies have found that DCs can also induce immune tolerance,and avoid or reduce the degree of transplant rejection.The aim of this study was to evaluate the effect of transfused immature CD4+ DCs on renal allografts in the rat model.Methods In this study,we induced CD4+ immature DCs from rat bone marrow cells by a cytokine cocktail.The immature CD4+ DCs were identified by morphological analysis and then the suppressive activity of these cells conditioned with donor kidney antigen was evaluated in vitro and in vivo.Results Immature CD4+ DCs conditioned with donor kidney antigen possessed immunosuppressive activity in vitro and they were able to prolong renal transplant survival in an allograft rat model in vivo.Conclusions Our study provides new information on efficacious renal transplantation,which might be useful for understanding the function of immature CD4+ DCs in modulating renal transplant rejection and improving clinical outcome in future studies.