IL17A and inflammatory bowel disease: Though the etiology and pathogenesis of IBD have not been elucidated, the imbalances between anti-inflammatory cytokines (e.g., interleukin (IL)-11, IL-10, IL-4) and pro-inflammatory cytokines (e.g., IL-β, IL-6, IL-12, IL-17A, interferon-γ (IL-γ), and tumor necrosis factor-α (TNF-α)) are supposed to play an essential role in modulating the inflammation [6,7].