To determine whether ILC2 can produce IL-5 following influenza infection in vivo, we first analyzed IL-5 production and the contribution of ILC2 as a source of IL-5 in adaptive immune cell deficient, IAV infected Rag2-/- mice since the majority of Thy1.2+ cells in these mice are ILC2 [10], [12], [24]. This evidence concerns the gene RAG2 and influenza.