Vitamin D3: a helpful immuno-modulator

The active metabolite of vitamin D, 1α, 25-dihydroxyvitamin D3 [1,25(OH)(2) D3], is involved in calcium and phosphate metabolism and exerts a large number ofbiological effects. Vitamin D3 inhibits parathyroid hormone secretion, adaptiveimmunity and cell proliferation, and at the same time promotes insulin secretion,innate immunity and stimulates cellular differentiation. The role of vitamin D3in immunoregulation has led to the concept of a dual function as both as animportant secosteroid hormone for the regulation of body calcium homeostasis and as an essential organic compound that has been shown to have a crucial effect on the immune responses. Altered levels of vitamin D3 have been associated, byrecent observational studies, with a higher susceptibility of immune-mediateddisorders and inflammatory diseases. This review reports the new developmentswith specific reference to the metabolic and signalling mechanisms associatedwith the complex immune-regulatory effects of vitamin D3 on immune cells