CARD11 signaling in regulatory T cell development and function.

Regulatory T cells (Tregs) are a critical subset of CD4 T cells that modulate the immune response to prevent autoimmunity and chronic inflammation. CARD11, a signaling hub and scaffold protein that links antigen receptor engagement to activation of NF-κB and other downstream signaling pathways, is essential for the development and function of thymic Tregs. Mouse models with deficiencies in CARD11 and CARD11-associated signaling components generally have Treg defects, but some mouse models develop overt autoimmunity and inflammatory disease whereas others do not. Inhibition of CARD11 signaling in Tregs within the tumor microenvironment can potentially promote anti-tumor immunity. In this review, we summarize evidence for the involvement of CARD11 signaling in Treg development and function and discuss key unanswered questions and future research opportunities.