IL-2 controls the stability of Foxp3 expression in TGF-β-induced Foxp3+ T cells in vivo (115.11)

Abstract

Abstract Stimulation of naïve mouse CD4+Foxp3- T cells in the presence of TGF-β results in the induction of Foxp3 expression and T suppressor function. However, Foxp3 expression in these induced Treg (iTreg) is unstable raising the possibility that iTreg would not be useful for treatment of autoimmune diseases. To analyze the factors that control the stability of Foxp3 expression in iTreg, we generated OVA-specific iTreg from OT-II Foxp3-GFP knock in mice. Following transfer to normal C57BL/6 mice, OT-II GFP+ cells maintained high levels of Foxp3 for 8 days. However, they rapidly lost Foxp3 expression upon stimulation with OVA in IFA in vivo. This unstable phenotype was associated with a strong methylation of the Treg-specific demethylated region (TSDR) within the Foxp3 locus. Administration of IL-2/anti-IL-2 complexes expanded the numbers of transferred Foxp3+ iTreg in the absence of antigen challenge. Notably, when the iTreg were stimulated with antigen, treatment with IL-2/anti-IL-2 complexes stabilized Foxp3 expression and resulted in enhanced demethylation of the TSDR. Conversely, neutralization of IL-2 diminished Foxp3 expression resulting in decreased suppressor function of the iTreg in vivo. Our data suggest that stimulation with TGF-β in vitro is not sufficient for imprinting T cells with stable Foxp3 expression. Administration of IL-2 in vivo stabilizes Foxp3 expression and may prove to be a valuable adjunct for the use of iTreg for the treatment of autoimmune diseases.