Biological factors acting as antigens can differentially induce Th1, Th2, and Th17 cell immune responses, leading to the release of IFN-gamma, IL-5/IL-13, and IL-17; subsequently, these immune response factors lead to the activation of the mononuclear, eosinophilic, and neutrophilic pathways, respectively, and contribute to the development of COPD, asthma, and lung cancer (Fig. 1b). Here, IL5 is linked to asthma.