Asthma symptoms in some patients may be exacerbated by chronic inflammation of the airways, largely mediated by type 2 inflammatory cytokines, in particular IL-13, which is produced by a variety of adaptive and innate immune cell types including CD4+ T cells, mast cells, basophils, and the recently described innate Th2 cells (ILC2) [82–85]. Here, IL13 is linked to asthma.