Development and function of intestinal innate lymphoid cells

► ILCs develop from common lymphoid progenitors, as lymphocytes do. ► Id2 and RORγt are necessary for the development of ILCs expressing IL-17 or IL-22. ► RORγt + ILCs play a central role in intestinal homeostasis and defense. ► RORγt + ILCs expressing IL-17 and IFNγ are also involved in pathological inflammation. ► Nuocytes, the ILCs for type 2 immunity, are early effectors against helminths.