Immunomodulatory Role of Vitamin D: A Review

Vitamin D is well known for its classical hormonal action related to the maintenance of mineral and skeletal homeostasis. However, the discovery that vitamin D receptor (VDR) is expressed in most non-skeletal tissues points to its broad role in the human organism. Current literature emphasizes a multidirectional role of vitamin D, with a special focus on its immunomodulatory properties. As VDR and the enzyme 1-α-hydroxylase are expressed in most immune cells, vitamin D modulates the phagocytic activity of macrophages and natural killer cells. In addition, it induces the microbicidal activity of phagocytes. In contrast, vitamin D suppresses differentiation and maturation of antigen-presenting dendritic cells and B lymphocytes, and it inhibits proliferation of Th1 and Th17 cells. In this review we aimed to describe the current scientific discoveries on the role of vitamin D as immunomodulator.