Neutralization of endogenous TGF-β abrogated TCR-induced Foxp3 expression. A. Western blot analysis of Foxp3 protein in cultured CD4+CD25- T cells with indicated reagents (72 hrs). B. FACS analysis of intracellular Foxp3 protein cultured with TCR and CD28 in the presence of anti-TGF-β1,2,3 (αTGF-β) or control (mIgG1) antibodies (72 hr). The data are shown for a representative donor. The values are presented as the percentage of CD25+Foxp3+ T cells. C. CD25+Foxp3+ T cells (%) in the TCR- and CD28-stimulated CD4+CD25- T cells in the absence (-) or presence of anti-TGF-β1,2,3 antibody (αTGF-β) at days 3 and 5. Each symbol represents one donor.