The release of cytokines is central to almost every stage of the immune response to allergens. During the induction phase, the differentiation of naïve T cells into T helper type 2 cells (Th2), enhances the secretion of IL-4 which stimulates clonal expansion. IL-4, IL-9, IL-13 induce goblet cell hyperplasia and promote mucus production. IL-4 and IL-13 also affect B cells to produce allergen specific antibodies.
Cytokine production is important for both the early and late phases of the asthmatic reaction. During the early phase reaction, allergen re-exposure triggers the release of cytokines that cause immediate hypersensitivity (IL-3, IL-4, IL-9, IL-13). During the late phase reaction, Th2- and mast cell-derived cytokines (IL-3, IL-5, GM-CSF) stimulate eosinophil activation and leukocyte recruitment to the site of allergen exposure. Finally, cytokine actions are important for the excessive inflammation and airway remodeling that characterizes late phase asthmatic reactions (IL-5, IL-9, IL-13, TNF).