IL-12 treatment increases expression of T-bet, a transcription factor associated with Th1 development [19, 20] ; we and others previously showed that T-bet was up-regulated in Tregs localized to sites of Th1-type inflammation [5, 7, 8] . Consistent with these results, T-bet was also increased in Foxp3 + Tregs as well as in Tconvs after IL-12 treatment (Fig. 2) .