IL17A and asthma: IFN-γ secreted by Th1 cells was reported to be necessary for efficient induction of Th2 responses [22, 23] and IL-17A secreted by Th17 is also known to be an inflammatory cytokine which induces eosinophilic and neutrophilic inflammations in asthma and allergic rhinitis and plays a role in activating mast cells [16, 24].