Treg-expression of CIS suppresses allergic airway inflammation through antagonizing an autonomous TH2 program

Maintenance of regulatory T (Treg) cells is crucial for the regulatory function of Treg cells in immune homeostasis and self-tolerance; however, the detailed underlying mechanisms remain elusive. In the current study, we found that the cytokine suppressor CIS is required for maintenance of Treg cell identity. Mice with Treg specific Cis-deficiency displayed aggravated experimental allergic asthma and in adulthood, developed splenomegaly, lymphadenopathy and spontaneous eosinophilic airway inflammation, accompanied by accumulation of effector memory helper T (TH) cells. Cis-deficiency led to loss of Foxp3 expression and decrease in suppressive function of Treg cells. Cis-deficient Treg cells expressed TH2 cell signature genes, Gata3, Irf4 and Il4, and excessive IL-4-STAT6 signals resulted in repressive chromatin modification in the Foxp3 locus and permissive modification in the Il4 loci. In vitro, blockade of IL-4 restored the expression of Foxp3 and the suppressive function of iTreg cells. Thus, we identified a novel feedback loop in stabilization of Treg cells and suppression of TH2 type inflammation in a Treg-intrinsic manner.