TSLP and allergic asthma: Allergic asthma involves the production of cytokines such as IL-4, IL-5, and IL-13 produced by the classic Th2 cells, whereas in nonallergic asthma, the airway epithelium release mediators such as thymic stromal lymphopoietin (TSLP) IL-25, and IL-33 upon activation of pollutants or allergens; these cytokines, in turn, activate innate lymphoid cells–type 2 (ILC-2) to release IL-4, IL-5, and IL-13 [6].