TNFα调控单核/巨噬系统亚群平衡从而恢复ITP免疫耐受的机制研究

Primary immune thrombocytopenia (ITP) is an autoimmune abnormality-conducted thrombocytopenic syndrome. Monocyte/macrophage system plays an important role in mediating platelets destruction and sustaining immune tolerance. Our previous study has found the imbalance of subtypes of monocytes/macrophages which led to higher expression of TNFα and contributed to the loss of immune tolerance. TNFα blockade could restore the balance of monocyte/macrophage system and reduce the destruction of platelets. Those above indicate the potential therapeutic role of TNFα blockade in ITP. However, the mechanisms of how TNFα regulates monocyte/macrophage system remain unknown. Hereby we propose that there may be three ways that TNFα blockade can restore the balance of monocyte/macrophage system: by regulating the autophagy level of monocytes/macrophages, by selectively inducing the apoptosis of some subtypes of monoyctes/macrophages, and by directly influencing the differentiation process of monocytes/macrophages. This research aims to demonstrate the role and mechanisms of how TNFα can regulate monoycte/macrophage system in cellular and molecular level, and we will do a series of in vitro and in vivo studies such as cell culture, establishing active and passive murine models to investigate the therapeutic value of TNFα blockade in ITP and provide new insights in the diagnosis and treatment of ITP.

原发免疫性血小板减少症（ITP）是一种自身免疫功能异常导致的血小板减少综合征，单核/巨噬系统在血小板破坏和免疫耐受的维持过程中起着重要作用。我们前期研究发现，ITP患者单核/巨噬系统各亚群平衡失调，导致TNFα表达增加，促使免疫耐受失衡。而TNFα阻断后可以恢复单核/巨噬系统亚群平衡，减少血小板的破坏。提示我们TNFα阻断对ITP具有潜在的治疗价值，而其对单核/巨噬系统具体的调控机制尚不明确。我们推测TNFα阻断可能通过选择性诱导单核/巨噬系统某些亚群的自噬、凋亡过程或者直接影响单核/巨噬细胞各亚群的分化过程从而影响各亚群间的平衡。本研究拟通过体外细胞培养以及构建主动型及被动型ITP小鼠模型，从细胞和分子水平揭示TNFα对单核/巨噬系统亚群的调控作用及其调控机制，探讨TNFα阻断对ITP的治疗价值，为临床诊疗提供新的思路。

原发性免疫性血小板减少症(ITP)是一种获得性自身免疫性出血性疾病。免疫耐受失衡导致的单核/巨噬细胞对血小板的过度清除是ITP重要的发病机制。单核/巨噬细胞通过膜表面的Fcγ受体识别经自身抗体致敏的血小板从而介导血小板的吞噬并释放炎性因子，引起炎症反应。FcγRIII（CD16）是一种活化型Fcγ受体，与巨噬细胞的吞噬功能密切相关。根据膜表面CD16的表达可以将单核细胞进一步分群，CD16+单核细胞亚群主要分泌肿瘤坏死因子-α（TNF-α），与机体炎症反应密切相关。在本研究中，我们发现ITP患者TNF-α的表达以及CD16+单核细胞的比例较正常人升高，并且与血小板数呈负相关性。同时，在体外试验中，TNF-α中和抗体可以通过抑制NF-κB信号通路降低ITP患者M1型巨噬细胞的极化，降低巨噬细胞吞噬血小板的功能以及对T细胞增殖的促进作用。最后，在ITP被动和主动小鼠模型中，TNF-α阻断对ITP模型鼠具有治疗作用，可以恢复ITP小鼠的血小板数目，降低ITP小鼠M1型巨噬细胞和非经典型单核细胞的比例，同时能够减少肝脏、脾脏对血小板的潴留。本研究发现TNF-α在ITP的疾病过程中具有重要调控作用，并提出TNF-α阻断可能是ITP新的治疗策略。