Eosinophils produce and secrete fibrogenic factors, such as fibroblast growth factor (FGF), heparin binding epidermal growth factor, IL-4, IL-13, IL-17, nerve growth factor, platelet derived growth factor, and transforming growth factor-β (TGF-β), leading to the development of severe asthma [60, 61]. This evidence concerns the gene IL4 and asthma.