IL17A and colitis: This has been attributed to the physiologic role of IL-17A in maintaining the integrity of the intestinal epithelium and protecting against some infections; on the other hand, the suppression of IL-17F, but not of IL-17A, provides protection against colitis by inducing Treg cells in a mouse model, suggesting that IL-17A and IL-17F may play distinct roles in the digestive tract [12].