Emerging data indicate that complement and neutrophils are involved in the maladaptive host immune response that fuels hyper-inflammation and thrombotic microangiopathy increasing the mortality rate in coronavirus disease 2019 (COVID-19). Here, we investigated the interaction between complement and the platelet/neutrophil extracellular traps (NETs)/thrombin axis, using COVID-19 clinical samples, cell-based inhibition studies and NETs/human aortic endothelial cell (HAEC) co-cultures. Increased plasma levels of NETs, TF activity and sC5b-9 were detected in patients. Neutrophils yielded high tissue factor (TF) expression and released NETs carrying functionally active TF. Confirming our ex vivo findings, treatment of control neutrophils with COVID-19 platelet-rich plasma generated TF-bearing NETs that induced thrombotic activity of HAEC. Thrombin or NETosis inhibition or C5aR1 blockade attenuated platelet-mediated NET-driven thrombogenicity. Serum isolated from COVID-19 patients induces complement activation in vitro, which is consistent with high complement activity in clinical samples. Complement inhibition at the level of C3 with compstatin Cp40 disrupted TF expression in neutrophils. In conclusion, we provide a mechanistic basis that reveals the pivotal role of complement and NETs in COVID-19 immmunothrombosis. This study supports emerging strategies against SARS-CoV-2 infection that exploit complement therapeutics or NETosis inhibition.

中文翻译：

---

补体和富含组织因子的嗜中性白细胞胞外陷阱是COVID-19免疫血栓形成的关键驱动因素

新兴数据表明补体和中性粒细胞参与了适应不良的宿主免疫反应，助长了过度炎症和血栓性微血管病，增加了2019年冠状病毒病（COVID-19）的死亡率。在这里，我们使用COVID-19临床样品，基于细胞的抑制研究和NETs /人主动脉内皮细胞（HAEC）共培养，研究了补体与血小板/嗜中性粒细胞细胞外捕获物（NETs）/凝血酶轴之间的相互作用。在患者中检测到血浆NETs，TF活性和sC5b-9升高。中性粒细胞产生高组织因子（TF）表达，并释放出携带功能性活性TF的NET。证实我们的离体研究结果，用富含COVID-19的血小板血浆处理对照中性粒细胞产生了含TF的NET，可诱导HAEC的血栓形成活性。凝血酶或NETosis抑制或C5aR1阻断减弱了血小板介导的NET驱动的血栓形成。从COVID-19患者中分离出的血清可在体外诱导补体激活，这与临床样品中的高补体活性是一致的。用坎普他汀Cp40在C3水平的补体抑制破坏了嗜中性粒细胞中的TF表达。总之，我们提供了一个机制基础，揭示了补体和NET在COVID-19免疫血栓形成中的关键作用。这项研究支持针对SARS-CoV-2感染的新兴策略，这些策略利用补体疗法或NETosis抑制作用。用坎普他汀Cp40在C3水平的补体抑制破坏了嗜中性粒细胞中的TF表达。总之，我们提供了一个机制基础，揭示了补体和NET在COVID-19免疫血栓形成中的关键作用。这项研究支持针对SARS-CoV-2感染的新兴策略，这些策略利用补体疗法或NETosis抑制作用。用坎普他汀Cp40在C3水平的补体抑制破坏了嗜中性粒细胞中的TF表达。总之，我们提供了一个机制基础，揭示了补体和NET在COVID-19免疫血栓形成中的关键作用。这项研究支持针对SARS-CoV-2感染的新兴策略，这些策略利用补体疗法或NETosis抑制作用。