Study Of Interleukin-18 And Interleukin-18 Receptor In Patients With Immune Thrombocytopenia

Background:Idiopathic thrombocytopenic purpura is an autoimmune hemorrhagic disease. It is characterized by more anti-platelet antibodies in vivo with increased platelet destruction of excessive bleeding. The pathogenesis is complex and may involve anfractuous relationship between T cells, B cells, megakaryocyte, cytokines, transcription factors and so on. Especially the T-cell immunity plays a key role in suppressing megakaryocytes and undermining platelets.The most early researches were focused on humoral immune abnormalities, proved that after the combination of the platelet antibodies and antigens, the sensitized platelets were phagocytized and destructed by reticuloendothelial system through Fc receptors (especially the spleen of mononuclear phagocyte), thereby causing the reduction in platelets. At present, as the study deepens, people turn to cell immune abnormalities, many researches involved that the co stimulatory signal of B7/CD28/CTLA-4 and CD40/CD40L may evoke the hyperpolarization of Thl cells in ITP patients.The current ITP pathogenesis focuses on the imbalance between Thl/Th2 cells, interleukin 18 (IL-18), as a strong inducer of inflammatory mediators of T cells, by stimulating the Thl-type response, can induce severe immune disorder.Most of the views [1,2] proved that the excessive polarization of Thl cells was an important mechanism leading to ITP occurred, but there are contrary or inconsistent reports.In this study, by detecting the upstream gene T-bet of Th cells (T-box expressed in cells), and GATA-3 (GATA binding protein-3) expression in ITP patients, for he first time used T-bet/GATA-3 as a sensitive indicator of imbalance of Thl/Th2 cells in ITP patients to verify the advantage response of Thl type cytokines in this disease, and reported the role of IL-18 and IL-18R in its pathogenesis and clinical treatment firstly.Purpose:Among newly diagnosed ITP patients before and after treatment,by detecting expression of interleukin-18 (IL-18) and CD3+cell surface IL-18 receptor a chain (IL-18Ra) in peripheral blood and expresson of transcription factor T-bet and GATA-3 mRNA in peripheral blood mononuclear cells, proved the role of IL-18 and IL-18R in Thl type cytokines advantage response and in pathogenesis of ITP patients.Method:Outpatient and inpatient treatment of 18 patients with newly diagnosed ITP in Qilu Hospital of Shandong University, as the research object. Detect expression of the upstream gene T-bet of Th cells (T-box expressed in cells)and GATA-3 (GATA binding protein-3) in peripheral blood mononuclear cells (peripheral blood mononuclear cells, PBMCs) using reverse transcriptase polymerase chain reaction (Reverse transcriptase polymerase chain reaction, RT-PCR);apply ELISA to detect the level of IL-18 in plasma; using flow cytometry detect expression of IL-18R in surface of CD3+cells and total lymphocytes; normal control were healthy volunteers matched with experimental groups.Main Results:The level of IL-18 in plasma of patients with newly diagnosed ITP was (468.57±141.62) pg/ml, significantly higher (P<0.05) than the controls. Expression of IL-18Ra on CD3+cell surface and lymphocyte surface, respectively (8.50±3.16)% and (9.16±2.98)%, no statistical significance between the two, but both were significantly higher (P<0.05) than the controls; In PBMCs, the level of IL-18 mRNA, T-bet mRNA, and GATA-3 mRNA were 0.12±0.02,0.07±0.02 and 0.0039±0.0014, that of IL-18 mRNA and T-bet mRNA were significantly higher (RR= 1.66 and 3.65, P<0.05) than the controls, while that of GATA-3 mRNA was significantly lower than the control group (down to 0.69 times the normal controls, P<0.05), T-bet/GATA-3 increased significantly. In remission stage of ITP,the levels of T-bet mRNA and GATA-3 mRNA had no statistical significance (P> 0.05) compared with normal controls, T-bet/GATA-3 returned to normal; in plasma the expression of IL-18R on IL-18 and CD3+ cell surface were also largely back to normal.Conclusion:IL-18 had a relationship with the occurrence of ITP development, ITP patients with active stage showed the characteristics of Thl advantage response, T-bet/GATA-3 mRNA obvious imbalance, T-bet/GATA-3 in patients with ITP can be used as a sensitive indicator for polarized Thl type cells. The study firstly proved that IL-18 and IL-18R may upregulate the expression of Thl type cells in ITP patients through protein and gene levels, by adjusting the ratio of T-bet/GATA-3restore the Thl/Th2 balance.It was expected to provide a new strategy or therapeutic targets for the treatment of ITP.