1,25-dihydroxyvitamin D3 inhibits the differentiation and migration of TH17 cells to protect against experimental autoimmune encephalomyelitis

Abstract

Background: Vitamin D3, the most physiologically relevant form of vitamin D, is an essential organic compound that has been shown to have a crucial effect on the immune responses. Vitamin D3 ameliorates the onset of the experimental autoimmune encephalomyelitis (EAE); however, the direct effect of vitamin D3 on T cells is largely unknown. Methodology/Principal Findings: In an in vitro system using cells from mice, the active form of vitamin D3 (1,25-dihydroxyvitamin D3) suppresses both interleukin (IL)-17-producing T cells (TH17) and regulatory T cells (Treg) differentiation via a vitamin D receptor signal. The ability of 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) to reduce the amount of IL-2 regulates the generation of Treg cells, but not TH17 cells. Under TH17-polarizing conditions, 1,25(OH)2D3 helps to increase the numbers of IL-10-producing T cells, but 1,25(OH)2D3's negative regulation of TH17 development is still defined in the IL-10-/- T cells. Although the STAT1 signal reciprocally affects the secretion of IL-10 and IL-17, 1,25(OH)2D3 inhibits IL-17 production in STAT1-/- T cells. Most interestingly, 1,25(OH)2D3 negatively regulates CCR6 expression which might be essential for TH17 cells to enter the central nervous system and initiate EAE. Conclusions/Significance: Our present results in an experimental murine model suggest that 1,25(OH)2D3 can directly regulate T cell differentiation and could be applied in preventive and therapeutic strategies for TH17-mediated autoimmune diseases. © 2010 Chang et al.