Vitamin D and 1,25-dihydroxyvitamin D3 as modulators in the immune system.

Treatment from weaning until old age with 1,25-dihydroxyvitamin D (1,25(OH)(2)D(3)) prevents diabetes in NOD mice. It is mainly through its actions on dendritic cells (DCs), that 1,25(OH)(2)D(3) changes the function of potentially autoreactive T lymphocytes. In contrast, early life treatment (from 3 to 70 days of age) of NOD mice with vitamin D or 1,25(OH)(2)D(3) did not influence final diabetes incidence at 200 days of age.