40 years later: Why do immune cells have vitamin D receptors?

Maternal vitamin D status is a critical factor that shapes the immune response of the offspring over the lifespan. Immune cells express vitamin D receptors and can produce local 1,25(OH)₂D. The ability of vitamin D to resolve inflammation and restrain pro-inflammatory T cells are central to the benefits of vitamin D both in autoimmunity and host resistance to infection. The functions of vitamin D to suppress T cells seems in conflict with the benefits of vitamin D in host immunity to some infections. Critical features by which vitamin D restores homeostasis following an immune challenge, include a delay in the production of 1,25(OH)₂D that coincides with the maximal expression of the VDR locally. In addition, vitamin D increases IL-10 and regulatory T cells. Controlling the magnitude of the immune response is a central feature for vitamin D as a regulator of the immune system. In the absence of vitamin D, inflammation accumulates and contributes to the pathogenesis of autoimmune and infectious diseases.