Furthermore, mainly based on analyses in preclinical murine models with CF-like pathology, Moretti et al. demonstrated that ILC2-derived IL-9 triggers an auto-amplifying pro-inflammatory cycle via activation of mast cells, which in turn supports ILC2 functions by producing the growth factor IL-2, indicating an orchestrating role of lung-resident ILC2s in CF-associated inflammation (14). The gene discussed is IL9; the disease is cystic fibrosis.