Anti-inflammatory role of IL-17 in experimental autoimmune uveitis

Previous studies have shown that IL-17 is a strong proinflammatory cytokine and that IL-17-producing autoreactive T cells play a major role in the pathogenesis of autoimmune diseases. In a previous study, we showed that injection of experimental autoimmune uveitis-susceptible mice with anti-IL-17 Abs blocked subsequent disease development. To determine whether administration of IL-17 to experimental autoimmune uveitis-susceptible Lewis rats and B10RIII mice injected with disease-inducing peptides enhanced disease susceptibility, we injected the recipient animals with various doses of human rIL-17 (hIL-17). Unexpectedly, the treated animals showed significant amelioration of disease; in addition, both the intensity of the autoreactive response and cytokine production by the autoreactive T cells induced by immunization with uveitogenic peptides were significantly decreased. Our results show that IL-17 has anti-inflammatory activity and that this cytokine can suppress the development of autoimmune disease.