IL17A and arthritic joint disease: This is consistent with previous studies that have demonstrated that the bioactive metabolite of vitamin D, 1,25(OH)2D, induces CD4+CD25+ T-reg cells (which mediates tolerance to transplantation and suppress autoimmune diabetes), suppress the production of Th-1/Th-17 cytokines e.g. IFN-γ and IL-17, and can suppress several Th-1/Th-17 inflammatory autoimmune diseases such as arthritis, lupus and inflammatory bowel disease [37], [38].