IL17A and multiple sclerosis: IL-17 is a pro-inflammatory cytokine with important antibacterial and antifungal effects.40 Direct antiviral effects of IL-17 have been detected in vaccinia virus41 and hepatitis B virus models.42 On the other hand, inadequately regulated IL-17 responses have been linked to various autoimmune phenomena such as multiple sclerosis,43, 44 RA45, 46 and inflammatory bowel diseases.47, 48 Expression of intracellular IL-17 is also associated with T-cell activation.