However, Yang et al. showed IL-17F was more critical than IL-17A in inducing airway inflammation and colitis [23], and Watanabe et al. found IL-17F is a stronger inducer of IL-8 released by keratinocytes and cystic fibrosis, which suggests that IL-17F might play a more prominent role in psoriasis [21, 22]. This evidence concerns the gene IL17A and colitis.