IL9 and asthma: ILC2s do not depend on T cells and secrete a large number of type 2 cytokines (such as IL-4, IL5, IL-9, and IL-13) under the function of IL-25, IL-33 and thymic stromal lymphopoietin (TSLP) to participate in asthma, virus infection and worm-host defense related with the type 2 immune response16.