Infection with the pandemic human coronavirus SARS-CoV-2 elicits a respiratory tract disease, termed Coronavirus disease 2019 (COVID-19). While a variable degree of disease-associated symptoms may emerge, severe COVID-19 is commonly associated with respiratory complications such as acute respiratory distress syndrome (ARDS), the necessity for mechanical ventilation or even extracorporeal membrane oxygenation (ECMO). Amongst others, disease outcome depends on age and pre-existing conditions like cardiovascular diseases, metabolic disorders but also age and biological sex. Intriguingly, increasing experimental and clinical evidence suggests that an exacerbated inflammatory response and in particular IgG immune complexes (ICs), significantly contribute to severe and prolonged COVID-19 disease progression. Vast amounts of deposited, unresolved ICs in tissue are capable to initiate an exaggerated Fc gamma receptor (FcγR) mediated signalling cascade which eventually results in common IC-associated organ diseases such as vasculitis, glomerulonephritis and arthritis, comorbidities that have been frequently reported for COVID-19. Moreover and independent of deposited ICs, very recent work identified soluble ICs (sIC) to be also present in the circulation of a majority of severely ill patients, where their systemic abundance correlated with disease severity. Thus, detection of circulating sICs in patients represents a potential marker for critical COVID-19 disease progression. Their detection early after clinical deterioration might become an indicator for the requirement of prompt anti-inflammatory treatment. Here, we review the role of ICs in COVID-19 progression, their possible origins and potential intervention strategies.

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中文翻译：

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免疫复合物是严重 COVID-19 免疫病理学的罪魁祸首

感染大流行性人类冠状病毒 SARS-CoV-2 会引发呼吸道疾病，称为冠状病毒病 2019 (COVID-19)。虽然可能会出现不同程度的疾病相关症状，但严重的 COVID-19 通常与呼吸系统并发症有关，例如急性呼吸窘迫综合征 (ARDS)、机械通气甚至体外膜肺氧合 (ECMO) 的必要性。其中，疾病结果取决于年龄和既往病症，如心血管疾病、代谢紊乱，还取决于年龄和生理性别。有趣的是，越来越多的实验和临床证据表明，炎症反应加剧，尤其是 IgG 免疫复合物 (IC)，会显着导致严重和长期的 COVID-19 疾病进展。大量存入，组织中未解决的 IC 能够启动放大的 Fc γ 受体 (FcγR) 介导的信号级联，最终导致常见的 IC 相关器官疾病，例如血管炎、肾小球肾炎和关节炎，以及经常报告的 COVID-19 合并症。此外，独立于沉积的 IC，最近的研究发现可溶性 IC (sIC) 也存在于大多数重病患者的循环中，其全身丰度与疾病严重程度相关。因此，在患者体内检测循环 sICs 代表了 COVID-19 疾病进展的潜在标志物。它们在临床恶化后的早期检测可能成为需要及时抗炎治疗的指标。在这里，我们回顾了 IC 在 COVID-19 进展中的作用，

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