Decreased 1,25-Dihydroxyvitamin D3 level is involved in the pathogenesis of Vogt-Koyanagi-Harada (VKH) disease.

1,25-Dihydroxyvitamin D(3) [1,25(OH)(2)D(3)] has recently been found to be involved in the development of autoimmune diseases. This study was to investigate the expression and potential role of 1,25(OH)(2)D(3) in the pathogenesis of Vogt-Koyanagi-Harada (VKH) disease. Blood samples were obtained from VKH patients and healthy individuals. Serum 1,25(OH)(2)D(3) levels were measured using ELISA. Peripheral blood mononuclear cells (PBMCs) or cluster of differentiation (CD) 4(+) T cells were cultured with or without 1,25(OH)(2)D(3) in the presence of anti-CD3 and anti-CD28 for the measurement of cell proliferation and cytokines. The cell proliferation was detected using the Cell Counting Kit. The levels of interleukin (IL)-17 and interferon (IFN)-γ levels in the supernatants of PBMCs or CD4(+) T cells were detected by ELISA. 1,25(OH)(2)D(3) was significantly decreased in the serum of active VKH patients as compared with inactive VKH patients and controls. It significantly inhibited PBMCs proliferation and CD4(+) T cell proliferation. It was also able to significantly inhibit the production of IL-17 and IFN-γ by both PBMCs and CD4(+) T cells from VKH patients and controls. These findings suggest that decreased expression of 1,25(OH)(2)D(3) may be involved in the development of VKH disease. 1,25(OH)(2)D(3) may be potentially used in the treatment of this disease.