ICOS signaling limits regulatory T cell accumulation and function in visceral adipose tissue

inflammation and helps preserve insulin sensitivity. Inducible T cell co-stimulator (ICOS) is highly expressed on effector (e)TRs that migrate to nonlymphoid tissues, and contributes to their maintenance and function in models of autoimmunity. In this study, we report an unexpected cell-intrinsic role for ICOS expression and downstream phosphoinositide 3-kinase (PI3K) signaling in limiting the abundance, VAT-associated phenotype, and function of TRs specifically in VAT. Icos-/- mice and mice expressing a knock-in form of ICOS that cannot activate PI3K had increased VAT-TR abundance and elevated expression of canonical VAT-TR markers. Loss of ICOS signaling facilitated enhanced accumulation of TRs to VAT associated with elevated CCR3 expression, and resulted in reduced adipose inflammation and heightened insulin sensitivity in the context of a high-fat diet. Thus, we have uncovered a new and surprising molecular pathway that regulates VAT-TR accumulation and function. immune tolerance and for the resolution of ongoing inflammation after infection (Dominguez-Villar and Hafler, 2018; Noval Rivas and Chatila, 2016; Smigiel et al., 2014a). Specialized subsets of tissue-specific TRs also function in tissue repair and homeostasis. For example, Areg* TRs expand in skeletal muscle and the lungs in response to injury and are required for proper tissue repair (Arpaia et al., 2015; Burzyn et al., 2013), whereas TRs within hair follicles and skin are essential for hair generation

Automated summary

The study revealed a surprising role of ICOS expression and PI3K signaling in limiting the abundance and function of TRs specifically in visceral adipose tissue, leading to reduced adipose inflammation and heightened insulin sensitivity.