Inflammatory bowel disease (IBD) includes ulcerative colitis (UC) and Crohn’s disease (CD), characterized pathologically by intestinal oxidative stress, nitrosative stress, leukocyte infiltration, elevated levels of pro-inflammatory cytokines (Th1-type cytokines IL-12, IFN-γ, TNF-α, IL-1, and Th17-type cytokine IL-17), and decreased levels of anti-inflammatory cytokines (Th2-type cytokines IL-4, IL-5, IL-10) (Table 2) (Zhang et al., 2006). Here, IL17A is linked to inflammatory bowel disease.