IL1RL1 and colitis: Specifically, our data imply that Il10-expressing ST2 Treg cells are highly susceptible to PI3Kδ inhibition, leading to a decrease in their abundance and thus to a disruption of gut homeostasis by causing a rapid expansion of pathogenic TH17 and TC17 cells that, together with a decrease in innate-like CD8+ T cells, cause colitis.