Interleukin 17F (IL-17F) and IL-17A are two closely related members of the IL-17 family with approximately 50% amino acid homology.IL-17F is derived from different cell types, such as Th17 cells, mast cells, and basophils, and is widely expressed in tissues, including the lung.IL-17F induces a number of cytokines and adhesion molecules in bronchial epithelial cells, vascular endothelial cells, adult fibroblasts, and many cytokines, chemokines, and adhesion molecules in eosinophils.IL-17F utilizes IL-17RA and IL-17RC as its receptors to activate the MAP kinase-related pathway. Overexpression of the IL-17F gene in mouse airways is associated with increased neutrophilia, induction of multiple cytokines, airway hyperresponsiveness, and mucus hypersecretion in the airways. Thus, IL-17F may play an important role in allergic airway inflammation and have important therapeutic implications for asthma.