TCR induced CD25+Foxp3+ T cells were immunosuppressive to CD4+CD25- T cell proliferation in vitro. A. CD4+CD25- T cells were cultured with anti-CD3 and anti-CD28 for 5 days. The converted CD4+CD25+Foxp3+ T cells were purified and washed extensively. The converted Tregs were then used at varying concentrations in a co-culture suppression assay along with CD4+CD25- (5 × 104) T cells pre-labeled with CFSE as responders and autologous monocytes (2 × 105) as accessory cells. Anti-CD3 antibody was added into the start of the co-culture suppression assay (0.5 μg/ml). CFSE dilution of responder cells was measured after 72 hrs using flow cytometry. B. IFN-γ production of responder cells in the co-culture assay as detected by flow cytometry after 72 hrs. iTreg: induced Foxp3+CD4+CD25+ T cells. The experiment was repeated for three times with similar results.