EmTh-1 cell–mediated inhibition of TGF-β–induced iTreg generation depends on IFN-γ. CD4⁺CD25⁻CD62L⁺ naive T cells were cultured for 72 hours with T-cell expander beads with or without TGF-β1 in the presence or absence of emTh-1 supernatant and with or without blocking antibodies against (A) mouse IFN-γ (*P < .05, a significant difference compared with the TGF-β + emTh-1 group) or (B) mouse TNF-α. (C-D) CD4⁺CD25⁻CD62L⁺ naive T lymphocytes were isolated from mouse spleens (IFN-γR^−/−) and cultured for 72 hours with T-cell expander beads with or without TGF-β1 and in the presence or absence of emTh-1 supernatant. Percentage of FoxP3-expressing cells was determined by flow cytometry. Results of 3 independent experiments have been combined. *P < .01, a significant difference compared with cells from wild-type (IFN-γR^+/+) mice cultured in the same conditions.