TSLP and chronic rhinosinusitis without nasal polyps: Basal stem cells co-expressing higher levels of TSLP and basal cell adhesion molecule were increased in the sinonasal mucosa of patients with CRSwNP versus those with CRSsNP, and their differentiation was prevented by a positive feedback loop in which basal cell adhesion molecule expression is reinforced by IL-4 and IL-13 [46].