ZFP36-family RNA-binding proteins in regulatory T cells reinforce immune homeostasis.

RNA binding proteins (RBP) of the ZFP36 family limit the differentiation and effector functions of CD4 and CD8 T cells, but little is known of their expression or function in regulatory T cells (Treg). By Treg-restricted deletion of Zfp36 family members we identify the essential role of Zfp36l1 and Zfp36l2 in Treg to maintain immune homeostasis. Mice with Tregs deficient in these RBP display an inflammatory phenotype with an expansion in the numbers of type-2 conventional dendritic cells, T effector cells, T follicular helper and germinal center B cells and elevated serum cytokines and immunoglobulins. In the absence of Zfp36l1 and Zfp36l2, the pool of cycling CTLA-4 in naïve Treg was reduced, Tregs were less sensitive to IL-2 and IL-7 but were more sensitive to IFNγ. In mice lacking both RBP in Treg, the deletion of a single allele of Ifng is sufficient to ameliorate the pathology. Thus, ZFP36L1 and ZFP36L2 regulate multiple pathways that enable Tregs to enforce immune homeostasis.