With regard to autoimmune diseases, 1,25(OH)2D3 has been shown to suppress type 1 diabetes in the non-obese diabetic (NOD) mouse model, to suppress experimental autoimmune encephalomyelitis (EAE) (a mouse model of multiple sclerosis (MS)), and to suppress mouse models of inflammatory bowel disease and systemic lupus erythematosus.1 Recent studies from Christakos’ lab have shown that inhibition of EAE is associated with inhibition of interleukin (IL)-17, a cytokine that plays a critical role in numerous inflammatory conditions and autoimmune diseases including MS. This evidence concerns the gene IL17A and autoimmune disease.