IL4 and asthma: Several cytokines can activate ILC2 in the early stage, epithelial-derived IL33 and TGFβ (60), as well as basophil-derived IL-4 (61), and tuft cell-derived IL-25 and CysLTs (62), of which the end product LTE4 is even detectable in the bronchoalveolar lavage fluid and urine of patients with asthma exacerbations (63).