Th17 cells produce IL-17 and have been implicated in the pathogenesis ofseveral autoimmune diseases, some experimental studies suggest that 1,25(OH)2D3 suppresses Th17 formation and activity [67,80,81,82,83] by blocking Nuclear Factor of Activated T-cells (NFAT) and Runt-related Transcription Factor 1 (RUNx1) binding to the IL-17 promoter and inducing Forkhead box P3 (FOXP3) [81], and by inhibiting RAR-related Orphan Receptor Gamma2 (RORγt) which is the transcription factor of IL-17 [84]. The gene discussed is IL17A; the disease is autoimmune disease.