The microbiota regulates type 2 immunity through RORγt+T cells

Changes to the symbiotic microbiota early in life, or the absence of it, can lead to exacerbated type 2 immunity and allergic inflammations. Although it is unclear how the microbiota regulates type 2 immunity, it is a strong inducer of proinflammatory T helper 17 (TH17) cells and regulatory T cells (Tregs) in the intestine. Here, we report that microbiota-induced Tregs express the nuclear hormone receptor RORγt and differentiate along a pathway that also leads to TH17 cells. In the absence of RORγt+ Tregs, TH2-driven defense against helminths is more efficient, whereas TH2-associated pathology is exacerbated. Thus, the microbiota regulates type 2 responses through the induction of type 3 RORγt+ Tregs and TH17 cells and acts as a key factor in balancing immune responses at mucosal surfaces.