[Objective]This study was designed to investigate capability of the conditioned media that originated from Renca cells to convert CIM~+ CD25~- T cells into CD4~+ CD25~+ T cells,which can exert immunosuppressive effect on effector T cells in vitro and in vivo.[Methods]The common media were mixed with the conditioned media at different ratios,and fresh enriched CD4~+ CD25~- T cells with MACS were cultured in mixed media for 7 days.At end-point of culture,the cells were collected and detected phenotypes in flow cytometer.Moreover,we detected immunosuppressive effect of converted CD4~+ CD25~+ T cells on effeetor T cells proliferation in one-way mixed lymphocytes reaction by using CCK-8,and we observed survival time and histology of grafts.The delayed type hypersensitivity was determined 14 days after transplantation.[Results]The mixed media could increase ratio of CD4~+ CD25~+ Foxp3~+ T cells in conditioned media ratio-dependent(P＜0.05),compared with control groups,when the mixed media contained no mote than 75% of conditioned media.The converted CD4~+ CD25~+ T cells significantly suppress proliferation of effector T cells in vitro,and prolong survival time of grafts,which were(29.6±1.4)d in converted CD4~+ CD25~+ T cells treated groups(P＜0.05),compared with that in untreated groups(9.8±0.6 d)or PBS treated groups(10.9±0.6 d).Moreover,delayed-type hypersensitivity reaction were conducted at day 14 after transplantation in the recipients,and the results showed that less pad swelling in the group treated with converted CD4~+ CD25~+ T cells than other control groups was found,according to measurement of pad swelling.In addition,progressed to complete necrosis of grafts were exhibited in the mice treated with PBS and untreated mice,whereas better healing of grafts and less lymphocytes infiltration were displayed in the mice treated with converted CD4~+ CD25~+ T cells,which were similar to the mice treated with natural regulatory T cells.[Conclusion]The converted CD4~+ CD25~+ T cells with Renca conditioned media play suppressive role in vitro and in vivo.