IL17A and inflammatory bowel disease: Furthermore, a poor vitamin status has been proposed both as a marker of disease activity in inflammatory bowel diseases and as a predictor of poor response to biological therapy [22], supporting its role as an immunomodulatory hormone with an anti-inflammatory effect, mediated through a reduction of proinflammatory cytokines (IL-2, IL-6, TNF-α and IL-17) and an upregulation of cytokines such as IL-4, IL-5 and IL-13 [3].