CD4 and colitis: Gut inflammation–Human/patient data: IL17A expression is increased in inflammatory bowel disease, while neutralization of IL-17A has no effect or rather exacerbate CD (31).–Animal models: IL-17A neutralization exacerbates symptoms in DSS and CD4+ t cell transfer model of colitis, while reduced pathology in an IL-10-deficient colitogenic model. IL-17A has important roles in preserving the intestinal epithelial barrier in DSS mice (32, 33)