One probable consequence of these changes in IL-2R expression, in conjunction with IL-12-mediated decreases in IL-2 production, is that Tregs are less able to compete for the smaller amount of IL-2 present in the culture. These changes result in diminished Treg proliferation and perhaps decreased Treg Effects of IL-12 on IL-2 and IL-2R Expression PLOS ONE | www.plosone.org suppressive function on a per cell basis (as measured by decreased Foxp3 expression (Fig. 1E) ), resulting in decreased total Treg suppressive capacity in the culture.