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Brief Report
IntroductionInterleukin-18 (IL-18), a member of IL-1 cytokine family, is a potent interferon-γ (IFN-γ) inducing factor and is synthesized by Kupffer cells in the liver, pancreas, kidney, skeletal muscle, lung, osteoblasts, and keratinocytes.1-3 IL-18 binding protein (IL-18BP) is a constitutively secreted protein able to bind IL-18 with high affinity, providing a potential mechanism whereby IL-18 activity is regulated. 4 Idiopathic thrombocytopenic purpura (ITP) is an autoimmune disorder, characterized by early platelet destruction induced by autoantibodies directed against specific glycoproteins of platelet surface. 5,6 It has become evident that an increased Th1/Th2 ratio in the peripheral blood has been proposed to correlate with disease activity in ITP .7-9 The expression of IFN-γ, a typical Th1 cytokine, is significantly higher in active ITP patients. Our previous study confirmed that the plasma and mRNA levels of both IFN-γ and IL-18 in active ITP patients were increased significantly compared with the normal controls. And the plasma concentrations of IL-18 correlated with IFN-α. We also observed IL-18BP was not significantly elevated in ITP patients, which resulted in an elevated ratio of IL-18/IL-18BP in patients with active disease. The balance of IL-18/IL-18BP plays a role in progression of ITP.
10Glucocorticoids (GC) have been widely recognized as the most appropriate first-line treatment for ITP, 11 even if the best therapeutic approach is still a matter of debate. Recently, highdose dexamethasone (HD-DXM) in 4-day cycles has proven its clinical efficacy in the treatment of ITP.12,13 However, the effects of HD-DXM on the balance of IL-18/IL-18BP remains unclear. In the present study, plasma levels as well as mRNA expression of IL-18, IL-18BP in peripheral blood mononuclear cells (PBMCs) and in vitro PBMC cultivation were measured to investigate possible effects of HD-DXM on IL-18 activity in ITP patients.
Design and Methods
Clinical studySeventeen patients with newly diagnosed ITP (13 females and 4 males, age range 16-58 years, median 38 years) were Funding: this work was supported by grants from National Natural Science Foundation of China (30600259, 30600680, 30770922, 30800491, and 30801258), 973 Program (N. 2006 CB 503803) China 2007, and Taishan scholar project funding. Manuscript received on February 23, 2009. Revised version arrived on April 9, 2009. Manuscript accepted on May 11, 2009 To evaluate the effects of high-dose dexamethasone (HD-DXM) on the balance of interleukin-18 (IL-18) and its endogenous antagonist IL-18 binding protein (IL-18BP) in ITP patients, IL-18, IL-18BP as well as IFN-γ, IL-4 plasma levels and platelet counts were determined in 17 ITP patients receiving DXM 40 mg/day for four consecutive days and in 24 healthy subjects. Using RT-PCR, the mRNA expression of IL-18, IL-18BP, IFN-γ, IL-4, T-box (T-bet) and GATA-binding protein 3(GATA-3) were studied in all subjects. The in vitro effects of DXM on IL-18BP and IL-18 of peripheral blood mononuclear cells ...