Hypoxia is a pathological condition common to many diseases, although multiple organ injuries induced by hypoxia are often overlooked. There is increasing evidence to suggest that the hypoxic environment may activate innate immune cells and suppress adaptive immunity, further stimulating inflammation and inhibiting immunosurveillance. We found that dysfunctional immune regulation may aggravate hypoxia-induced tissue damage and contribute to secondary injury. Among the diverse mechanisms of hypoxia-induced immune dysfunction identified to date, the role of programmed death-ligand 1 (PD-L1) has recently attracted much attention. Besides leading to tumour immune evasion, PD-L1 has also been found to participate in the progression of the immune dysfunction which mediates hypoxia-induced multiple organ injury. In this review, we aimed to summarise the role of immune dysfunction in hypoxia-induced multiple organ injury, the effects of hypoxia on the cellular expression of PD-L1, and the effects of upregulated PD-L1 expression on immune regulation. Furthermore, we summarise the latest information pertaining to the involvement, diagnostic value, and therapeutic potential of immunosuppression induced by PD-L1 in various types of hypoxia-related diseases, including cancers, ischemic stroke, acute kidney injury, and obstructive sleep apnoea.

中文翻译：

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PD-L1在介导缺氧引起的多器官损伤的免疫功能障碍中的作用

缺氧是许多疾病常见的病理状态，但缺氧引起的多器官损伤常常被忽视。越来越多的证据表明，缺氧环境可能会激活先天免疫细胞并抑制适应性免疫，进一步刺激炎症并抑制免疫监视。我们发现功能失调的免疫调节可能会加重缺氧引起的组织损伤并导致继发性损伤。迄今为止，在缺氧引起的免疫功能障碍的多种机制中，程序性死亡配体1（PD-L1）的作用最近引起了广泛关注。除了导致肿瘤免疫逃避外，PD-L1 还被发现参与介导缺氧诱导的多器官损伤的免疫功能障碍的进展。本文旨在总结免疫功能障碍在缺氧引起的多器官损伤中的作用、缺氧对细胞PD-L1表达的影响以及上调PD-L1表达对免疫调节的影响。此外，我们总结了有关 PD-L1 诱导的免疫抑制在各种类型缺氧相关疾病（包括癌症、缺血性中风、急性肾损伤和阻塞性睡眠呼吸暂停）中的参与、诊断价值和治疗潜力的最新信息。