Decreased immunosuppressive actions of 1α, 25-dihydroxyvitamin D3 in patients with immune thrombocytopenia

Abstract Primary immune thrombocytopenia (ITP) is an acquired autoimmune disease. 1α, 25-dihydroxyvitamin D 3 [1,25(OH) 2 D 3 ] and vitamin D receptor (VDR) play important immune-suppressive roles in immune system. It has been reported that serum 1,25(OH) 2 D 3 were lower in ITP patients. In this study, we evaluated local 1,25(OH) 2 D 3 level and VDR mRNA expression further, and determined whether 1,25(OH) 2 D 3 /VDR were correlated with T cell dysfunction in ITP patients. We found that 1,25(OH) 2 D 3 /VDR levels were decreased in active ITP patients, and 1,25(OH) 2 D 3 had significant anti-inflammatory effects on ITP patients, including both anti-proliferation of peripheral blood mononuclear cells (PBMCs) and reversing the abnormal T cells polarization. 1,25(OH) 2 D 3 inhibited the differentiation of T helper (Th)1 and Tc1 cells but induced the differentiation of Th2, Tc2 and T regulatory (Treg) cells in ITP patients. However, the percentage of Th17 cells were not affected obviously with 1,25(OH) 2 D 3 . In addition, 1,25(OH) 2 D 3 also suppressed pro-inflammatory cytokines (INF-γ and IL-17A) but promoted anti-inflammatory cytokine (IL-10) secretion in ITP patients. In conclusion, decreased 1,25(OH) 2 D 3 /VDR might participate in the pathogenesis of ITP, and appropriate supplement of 1,25(OH) 2 D 3 may be a promising treatment.