Purified naive CD4+ T cells from CbfbF/F CD4-cre and control CbfbF/+ CD4-cre mice (Cd45.2) harboring a Foxp3-ires-GFP allele (Bettelli et al., 2006) were stimulated in vitro with anti-CD3/28 mAbs, IL-2, and TGF-β.