Figure 1. Contribution of ILC2s by the bone marrow and thymus. In the bone marrow, a variety of progenitor subsets (collectively called ILCP) have been shown to descend from CLP, and differentiate into all three ILC groups, but immature ILC2s (ILC2P) are more abundant. In the thymus, ETPs which arise from thymus-seeding progenitors generated in the bone marrow, as well as full-committed T cell precursors such as DN3 cells can differentiate into ILC2s, possibly through precursors similar to those found in the bone marrow. Newly made ILC2s and probably their progenitors then circulate in the blood and populate in tissues.