免疫性血小板减少症中单核/巨噬细胞调控浆细胞的作用及机制研究

Immune thrombocytopenia (ITP) is a common autoimmune bleeding disorder characterized by autoantibody-mediated platelet clearance by one’s own monocytes/macrophages, in which long-lived plasma cells (LLPC) play an important role via secreting antibodies persistently. Previous studies showed that plasma cells and autoantibody-secreting LLPCs were both increased in ITP patients. A Proliferation Inducing Ligand (APRIL), produced predominantly from monocytes/macrophages, is one of the major cytokines supporting the lifespan and maintaining the function of plasma cells. Our previous study demonstrated that aberrant macrophage polarization is involved in the pathogenesis of ITP, while all-trans retinoid acid (ATRA) could correct the impaired differentiation and malfunctions, which results in a satisfying outcome in steroid-resistant ITP patients. Here, our hypothesis is that monocytes/macrophages prolong the lifespan of plasma cells and promote the antibody-generation in ITP patients and ATRA could restore the function of monocytes/macrophages on plasma cells. This study will explore the impact of monocytes/macrophages on plasma cells through collecting ITP patients’ bone marrow and spleen samples, constructing APRIL lentivirus, and creating a macrophage APRIL-specific knockout mice to further develop our active ITP murine model. Our study will focus on the regulation mechanisms of monocytes/macrophages via both in vivo and in vitro studies to elucidate the pathogenesis of ITP and provide insights into novel therapeutic strategies in this field.

免疫性血小板减少症（ITP）是一种常见的自身免疫性出血性疾病，主要机制为患者体内产生抗血小板抗体，致敏血小板被单核/巨噬细胞过度吞噬。浆细胞为重要的抗体分泌细胞，前期研究发现ITP患者中浆细胞数量高于对照。浆细胞的长期生存及功能的维持有赖于增殖诱导配体（APRIL）等，而单核/巨噬细胞是APRIL的最主要来源，且研究发现单核/巨噬细胞与浆细胞的长期生存有密切关系。我们前期研究发现ITP患者体内巨噬细胞存在分化及功能异常的现象，全反式维甲酸（ATRA）能够纠正这种异常的分化及功能，并在激素耐药的ITP患者中疗效显著。据此我们推测巨噬细胞对浆细胞的异常调控参与了ITP的发病，而ATRA能纠正这种异常。我们将通过收集ITP患者标本，构建APRIL干扰病毒及特异性敲除巨噬细胞上APRIL的主动型ITP小鼠模型，从体外和体内两方面研究单核/巨噬细胞对浆细胞的调控作用及机制，为ITP的诊疗提供新思路。

免疫性血小板减少症（ITP）是一种常见的自身免疫性出血性疾病，主要机制为患者体内产生抗血小板抗体，致敏血小板被单核/巨噬细胞过度吞噬。浆细胞为重要的抗体分泌细胞， 前期研究发现ITP患者中浆细胞数量高于对照。浆细胞的长期生存及功能的维持有赖于增殖诱导配体（APRIL）等，而单核/巨噬细胞是APRIL的最主要来源，但单核/巨噬细胞是否能够影响浆细胞的分化、生存及功能目前尚不明确。我们的研究发现：1. ITP骨髓巨噬细胞上浆细胞生存相关细胞因子表达增加。ITP患者骨髓浆细胞比例升高，自身抗体阳性患者的长寿命浆细胞比例升高，提示ITP中巨噬细胞对骨髓浆细胞存在调控作用；2. ITP小鼠模型中，清除巨噬细胞后，浆细胞数目明显降低，具有分泌抗血小板抗体功能的浆细胞数目也明显降低，且骨髓中pre, pro B细胞比例增加，而成熟B细胞比例降低，提示巨噬细胞不仅影响浆细胞的生存及功能，同时影响B 细胞的分化成熟。3. 纠正ITP单核/巨噬细胞系统异常的药物可作为潜在治疗手段：（1）短链脂肪酸通过影响单核/巨噬细胞的代谢途径，抑制其产生炎性细胞因子、并抑制其吞噬能力及抗原递呈能力。（2）ITP患者体内人白细胞抗原-G（HLA-G）及其抑制性受体免疫球蛋白样转录物（ILTs）表达降低，且可溶性HLA-G表达水平与抗体水平负相关，但ITP患者B细胞表面HLA-G表达不低。应用rhHLA-G能够上调ILTs表达，HLA-G能够刺激Th2型分化，下调Th1、Th17免疫应答，rhHLA-G治疗后的树突状细胞抗原递呈能力降低，细胞对血小板的杀伤减弱。应用rhHLA-G与金纳米颗粒结合应用于主动型ITP小鼠，与对照组相比，明显提高血小板计数。因此，我们的研究发现ITP患者体内单核/巨噬细胞异常分泌浆细胞生长因子导致浆细胞及B细胞异常分化，药物干预纠正单核/巨噬细胞的异常能够缓解ITP患者症状。