Dietary Vitamin D Increases Percentages and Function of Regulatory T Cells in the Skin-Draining Lymph Nodes and Suppresses Dermal Inflammation.

Skin inflammatory responses in individuals with allergic dermatitis may be suppressed by dietary vitaminDthrough induction and upregulation of the suppressive activity of regulatory T(T-Reg) cells. Vitamin D may also promote T-Reg cell tropism to dermal sites. In the current study, we examined the capacity of dietary vitamin D-3 to modulate skin inflammation and the numbers and activity of T-Reg cells in skin and other sites including lungs, spleen, and blood. In female BALB/c mice, dietary vitamin D-3 suppressed the effector phase of a biphasic ear swelling response induced by dinitrofluorobenzene in comparison vitamin D-3-deficient female BALB/c mice. Vitamin D-3 increased the percentage of T-Reg (CD3+CD4+CD25+Foxp3+) cells in the skin-draining lymph nodes (SDLN). The suppressive activity of T-Reg cells in the SDLN, mesenteric lymph nodes, spleen, and blood was upregulated by vitamin D-3. However, there was no difference in the expression of the naturally occurring T-Reg cell marker, neuropilin, nor the expression of CCR4 or CCR10 (skin-tropic chemokine receptors) on T-Reg cells in skin, SDLN, lungs, and airway-draining lymph nodes. These data suggest that dietary vitamin D-3 increased the percentages and suppressive activity of T-Reg cells in the SDLN, which are poised to suppress dermal inflammation.