IL17A and autoimmune disease: Furthermore, the Th17 cell line produces IL-17, and has been implicated in the development of several autoimmune diseases; however, several experimental studies suggest that vitamin D3 suppresses Th17 formation and activity by blocking NFAT and runt-related transcription factor 1 (RUNX1), binding to the IL-17 promoter, and inducing FOXP3, in addition to inhibiting RAR-related orphan receptor γ2 (RORt), which is the transcription factor that regulates IL-17 [95].