The features of mild asthma in cluster 2 and the severe asthma in cluster 3 indicated according to clinical characteristics of patients in the present study were further supported by significant differences in sputum levels of traditional Th1/Th2/Th17 cytokines (IL-5, IL-4, IL-13, IFN-γ, TNF-α, IL-17) and the related epithelium-derived cytokine (IL-33); however, the sputum EOS counts were comparable between these two clusters. Here, IL4 is linked to asthma.