Endogenous Calcitriol Synthesis Controls the Humoral IgE Response in Mice.

The vitamin D receptor participates in the control of IgE class-switch recombination in B cells. The physiologic vitamin D receptor agonist, 1,25(OH)D (calcitriol), is synthesized by the essential enzyme 25-hydroxyvitamin D-1α-hydroxylase (CYP27B1), which can be expressed by activated immune cells. The role of endogenous calcitriol synthesis for the regulation of IgE has not been proven.

25-hydroxvitamin D3 promotes the long-term effect of specific immunotherapy in a murine allergy model.

Calcitriol (1α,25-dihydroxyvitamin D3) is the active vitamin D metabolite and mediates immunological functions, which are relevant in allergy. Its therapeutic use is limited by hypercalcaemic toxicity. We have previously shown that the activation of the vitamin D receptor inhibits IgE production and that B cells can synthesize calcitriol from its precursor 25-hydroxyvitamin D3 (inactive precursor) [25(OH)D] upon antigenic stimulation.