Canonical Wnt signaling negatively modulates T regulatory cell function

Foxp3 is crucial for both the development and function of regulatory T cells (Treg),however the post-translational mechanisms regulating Foxp3 transcriptional output remain poorly defined. Here, we demonstrate that TCF1 and Foxp3 interact in the nucleus of Treg, and that active Wnt-signaling disrupts Foxp3 transcriptional activity. Utilizing a global ChIP-seq comparison we demonstrate considerable overlap between Foxp3 and Wnt target genes in Treg. Activation of Wnt signaling significantly reduces Treg-mediated suppression both in vitro and in vivo, while disruption of Wnt signaling in Treg enhances their suppressive capacity. Activation of effector T cells increases Wnt3a production, and Wnt3a levels were found to be greatly increased in mononuclear cells isolated from synovial fluid versus peripheral blood of arthritis patients. We propose a model in which Wnt produced by activated mononuclear cells under inflammatory conditions represses Treg function allowing a productive immune response, but if uncontrolled could lead to the development of autoimmunity. Overall design: Beta catenin ChIP-seq in Treg