To examine the role of IL-12 in IFN-c induction in Tregs when inflammation is induced by a more physiological mechanism, we treated samples with TLR agonists, LPS or CpG. T cells (B6 or IL-12Rb2 2/2 ) and splenic DCs (B6) were isolated and incubated together in the presence of anti-CD3 mAb and LPS or CpG. The fraction of Tregs expressing IFN-c increased after LPS or CpG exposure and was similar to levels obtained in cultures treated with IL-12 (Fig. 3 ). LPS and CpG likely functioned via effects on DCs because no IFN-c was induced when unfractionated lymph nodederived lymphocytes were treated with LPS or CpG in the absence of added DCs (data not shown). CpG or LPS-mediated augmentation in the proportion of cells expressing IFN-c was largely dependent on IL-12, since the fraction of IFN-c + Tregs increased only slightly in cultures containing IL-12Rb2 2/2 T cells (Fig. 3) . Of note, IL-12Rb2 2/2 mice are deficient in IL-12 but not IL-23 signaling [21] .