IL-9 and c-Kit+ mast cells in allergic rhinitis during seasonal allergen exposure: Effect of immunotherapy

IL-9 is upregulated in the nasal mucosa during the pollen season and correlates with tissue infiltration by eosinophils. Successful pollen immunotherapy is associated with inhibition of seasonal increases in both nasal c-Kit+ mast cells and eosinophils. This effect might be explained, at least in part, by the reduced local expression of IL-9.