The vitamin D receptor is necessary for 1α,25-dihydroxyvitamin D3 to suppress experimental autoimmune encephalomyelitis in mice

The active metabolite of vitamin D, 1α,25-dihydroxyvitamin D3, suppresses autoimmune disease in several animal models including experimental autoimmune encephalomyelitis (EAE), a model of multiple sclerosis. The molecular mechanism of this immunosuppression is at present unknown. While 1α,25-dihydroxyvitamin D3 is believed to function through a single vitamin D receptor, there are reports of other vitamin D receptors as well as a “nongenomic” mode of action. We have prepared the EAE model possessing the vitamin D receptor null mutation and determined if 1α,25-dihydroxyvitamin D3 can suppress this disease in the absence of a functional vitamin D receptor. Vitamin D receptor null mice develop EAE although the incidence rate is one-half that of wild-type controls. The administration of 1α,25-dihydroxyvitamin D3 had no significant effect on the incidence of EAE in the vitamin D receptor null mice, while it completely blocked EAE in the wild-type mice. We conclude that 1α,25-dihydroxyvitamin D3 functions to suppress EAE through the well-known VDR and not through an undiscovered receptor or through a “nongenomic” mechanism.