Conserved developmental rewiring of the TCR signalosome drives tolerance in innate-like lymphocytes.

Natural intraepithelial T lymphocytes (T-IELs) are innate-like, intestine-resident T cells essential for gut homeostasis. These cells express self-reactive T cell antigen receptors (TCRs) due to thymic agonist selection, but they do not cause autoimmunity. The mechanism underlying natural T-IELs tolerance in the gut is unclear. Using TCR reporter mouse models and phosphoproteomics, we demonstrate that TCR signaling is intrinsically suppressed in natural T-IELs. We discover that this suppression occurs post-selection in the thymus through altered expression of TCR signalosome components, a mechanism we term RePrESS (Rewiring of Proximal Elements of TCR Signalosome for Suppression). RePrESS is evolutionarily conserved and also found in autoreactive innate-like T cells from skin, breast and prostate. In coeliac disease, tolerance breakdown is associated with loss of RePrESS in natural T-IELs. Our findings reveal a distinct, conserved mechanism of tolerance involving TCR signaling rewiring, with implications for understanding barrier tissue homeostasis and autoimmune disease.