Asthma is characterized by chronic inflammation of the airways, contraction of smooth muscle, overproduction of mucus, and remodeling of the airway wall. In many forms of asthma, there is an accumulation of eosinophils, which predicts a good response to inhaled glucocorticoids. Eosinophilic inflammation is controlled by type 2 helper T (Th2) lymphocytes of the adaptive immune system, which make interleukin-4, interleukin-5, and interleukin-13 in response to the presentation of an allergen by dendritic cells in the airway. However, many features of asthma can also be controlled by type 2 innate lymphoid cells, which cannot specifically recognize allergens but do produce . . .