Fig. 2.

Allergens stimulate structural cells (epithelial cells and smooth muscle cells) to produce different kinds of cytokines, including IL-5, IL-4, IL-13, and thymic stromal lymphopoietin (TSLP). This process activates naïve T-cells (Th0) to differentiate into Th1 and Th2 cells. The imbalance between these T-cells would lead to inflammation in asthma. Released cytokines from Th2 result in IgE production from B-cells, which bind to their receptors on mast cells. Mast cell-derived prostaglandin D2 (PGD2) and Th2 cytokines activate ILC2, which can provoke eosinophilia and hyperactivity in asthma. Th17 and IL-17 are involved in asthma exacerbation by recruitment of neutrophils