Abstract
Foxp3+ regulatory T cells (Tregs) can inhibit immune responses and maintain immune tolerance by secreting immunosuppressive TGF-β1 and IL-10. However, the efficiency of Tregs become the major obstacle to their use for immunotherapy. In this study, we investigated the relevance of the C-type lectin receptor CD69 to the suppressive function. Compared to CD4+Foxp3+CD69- Tregs (CD69- Tregs), CD4+Foxp3+CD69+ Tregs (CD69+ Tregs) displayed stronger ability to maintain immune tolerance. CD69+ Tregs expressed higher levels of suppression-associated markers such as CTLA-4, ICOS, CD38 and GITR, and secreted higher levels of IL-10 but not TGF-β1. CD69+ Tregs from Il10+/+ rather than Il10-/- mice significantly inhibit the proliferation of CD4+ T cells. CD69 over-expression stimulated higher levels of IL-10 and c-Maf expression, which was compromised by silencing of STAT3 or STAT5. In addition, the direct interaction of STAT3 with the c-Maf promoter was detected in cells with CD69 over-expression. Moreover, adoptive transfer of CD69+ Tregs but not CD69-Tregs or CD69+ Tregs deficient in IL-10 dramatically prevented the development of inflammatory bowel disease (IBD) in mice. Taken together, CD69 is important to the suppressive function of Tregs by promoting IL-10 production. CD69+ Tregs have the potential to develop new therapeutic approach for autoimmune diseases like IBD.