Fig. 2

Overview of vitamin D’s immunomodulation functions. Innate immune response: Vitamin D inhibits the maturation of dendritic cells and blocks their antigen presentation to T helper cells. Also, vitamin D induces the differentiation of macrophages and exerts direct antibacterial and antiviral actions through induction of cathelicidin and defensin peptides. Adaptive immune response: Vitamin D modulates the balance of T-helper subsets by inhibiting Th1 and Th17 effector cells, inducing Th2 cells, and enhancing the development of Treg cells. Vitamin D suppresses the release of pro-inflammatory cytokines including IL2, IL6, IL12, INFr, TNFa, NF-kB, etc., from both innate and adaptive immune responses