TGF-β secreted by CD4+ CD25+ FoxP3+ Tregs, but not by DCs, induces the expansion of Tregs. CD4+ T cells were pre-treated with inhibitor for TGF-β receptor for 1 hr and co-cultured with DCs, followed by resistin treatment for 4 days. Anti-human CD2 and CD3 antibodies were then added to the cells for an additional 3 days. (A) CD25+ FoxP3+ Tregs were measured by flow cytometry. (B) TGF-β production in the supernatant was measured by ELISA. (C) DCs were treated with various concentrations (0, 50, 100, 200 and 500 ng/ml) of resistin for 6 hrs and then TGF-β mRNA expression was measured by RT-PCR. * P< 0.05. The value in each panel indicates the percentage of CD25+ FoxP3+ Tregs. The results represent the mean ± standard deviation from three separate experiments.