Figure 1.

Pathophysiology of asthma. Alarmin cytokines IL-25, IL-33 and TSLP are released from the airway epithelium in response to external stimuli such as pathogens, allergens, and pollution. These cytokines result in the downstream production of type 2 cytokines (IL-4, IL-5, and IL-13) from Th2 cells and their innate counterpart, ILC2s. The type 2 cytokines induce airway inflammation, FeNO, airway hyperresponsiveness, and remodeling, all inhibited by corticosteroids. The production of histamine and leukotrienes from activated basophils and mast cells promotes bronchoconstriction, which is prevented by antagonists. FeNO = fractional exhaled nitric oxide; LABA = long acting β-agonist; SABA = short-acting β-agonis.