原发免疫性血小板减少症是一种复杂的，多种免疫机制共同参与的获得性自身免疫性出血性疾病，至今发病机制不明。近年来的研究认为, T细胞免疫异常在其发病中起到一定的作用，T细胞的活化需要协同刺激信号，来影响T 细胞的活化增殖或凋亡。我们在前期实验的研究中发现，共刺激分子的表达可能与ITP的发病有关。而负性共刺激途径程序性死亡分子PD-1及其配体PD-L1与多种免疫性疾病的免疫调节有关。本项目研究旨在通过检测ITP患者发病期及治疗后PD-1/PD-L1在T细胞上的表达及T细胞分泌的相关细胞因子的动态变化，探讨 PD-1/ PD-L1信号通路对ITP患者T细胞增殖的调控作用及其对细胞因子分泌的影响，来阐明该通路在ITP发病机制中所起的作用，从而为ITP的免疫靶向治疗提供新思路。

Primary immune thrombocytopenia (ITP) is a complicated, acquired, autoimmune hemorrhagic disease with many immune dysfunctions. The etiology of ITP remains unclear by now. Recent studies found that T-cell immune abnormalities played a role in the pathogenesis of ITP. T-cell activation require co-stimulatory signals which determine the activation、proliferation or apoptosis of T cell. Our previous study found that the expression of co-stimulatory factor may be related to ITP. Recently，programmed cell death molecule PD-1 and its ligand PD-L1 in the negative co-stimulatory pathways were discovered in immunology. This pair of molecules showed potential values in pathogenesis and treatment of this disease. The aim of the study is to explore the effect of PD-1 / PD- L1 signaling pathway in T cell proliferation, to elucidate its role in the pathogenesis of ITP and to provide theoretical basis for immune targeting prevention in ITP through researching the dynamic changes of PD-1/PD-L1 signaling pathway T cells and related cytokines in patients with ITP before and after treatment.