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 vitamin D through 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.