There is now convincing evidence that exposure to the ultraviolet (UV) component of sunlight protects us from developing a number of autoimmune diseases including type 1 diabetes, Juvenile onset Crohn’s, Crohn’s disease, colitis, Sjögren's syndrome and possibly rheumatoid arthritis. Central Nervous System (CNS)-autoimmune diseases such as multiple sclerosis (MS) show the most striking inverse correlation with UV. Recent studies have confirmed that higher UV amounts reduce the incidence of a patients first clinical diagnosis of CNS demyelination, many of whom will develop clinically confirmed MS. This is important because it shows that UV is able to prevent both the development and progression of MS. However, despite intense community interest in understanding how increasing the amount of UV we receive leads to a reduction in autoimmune diseases, the mechanisms by which UV provides this protection remains unknown. We have used the murine CNS autoimmune model, experimental autoimmune encephalomyelitis (EAE) to demonstrate that exposure to UV protects mice from autoimmune disease. Others have demonstrated that this protection from EAE is not mediated by UV-induced Vitamin D3 suggesting another UV-induced event is responsible for protection from autoimmune disease. We hypothesise that UV-suppression of the immune system via the activation of regulatory lymphocytes is the mechanism by which sunlight protects from autoimmunity