Review Article Role of Th17 Cells in the Pathogenesis of Human IBD

permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. The gastrointestinal tract plays a central role in immune system, being able tomount efficient immune responses against pathogens, keeping the homeostasis of the human gut. However, conditions like Crohn’s disease (CD) or ulcerative colitis (UC), themain forms of inflammatory bowel diseases (IBD), are related to an excessive and uncontrolled immune response against normal microbiota, through the activation of CD4+ T helper (Th) cells. Classically, IBD was thought to be primarily mediated by Th1 cells in CD or Th2 cells in UC, but it is now known that Th17 cells and their related cytokines are crucial mediators in both conditions. Th17 cells massively infiltrate the inflamed intestine of IBD patients, where they produce interleukin- (IL-) 17A and other cytokines, triggering and amplifying the inflammatory process. However, these cells show functional plasticity, and they can be converted into either IFN