Vitamin D and the immune system: new perspectives on an old theme.

It is almost 30 years since an interaction between vitamin D and the immune system was first documented. Although this was initially proposed as a nonclassic effect of vitamin D associated with granulomatous diseases, our current view is now changed considerably. Recent studies have shown a potential physiologic role for vitamin D in regulating normal innate and adaptive immunity. Future studies now need to focus on the clinical implications of vitamin D–mediated immunity and, in particular, the possible beneficial effects of supplementary vitamin D with respect to infectious and autoimmune diseases.