IL17A and colitis: Evidences have demonstrated that H. pylori infection decreased the pro-inflammatory cytokines (TNF-α, IFN-γ, IL-1β, IL- 6, IL-17A and IL23) in colitis mouse models [6, 10], and we also have reported that IL-6 and IL23 expression were down-regulated in H. pylori-infected chronic colitis mice.