In patients with asthma as well as in mouse models of experimental allergic asthma, development of AHR is closely associated with the influx of eosinophils into the airway tissue and bronchoalveolar lumen, and eosinophils have been shown to contribute to the development of AHR by releasing not only an array of cationic proteins but also neurotrophins (46–48). This evidence concerns the gene BDNF and allergic asthma.