Effective and efficient efferocytosis of dead cells and associated cellular debris are critical to tissue homeostasis and healing of injured tissues. This important task was previously thought to be restricted to professional phagocytes (PPs). However, accumulating evidence has revealed another type of phagocyte, the amateur phagocyte (AP), which can also participate in efferocytosis. APs are non-myeloid progenitor/nonimmune cells that include differentiated cells (e.g., epithelial cells, fibroblasts, and endothelial cells [ECs]) and stem cells (e.g., neuronal progenitor cells and mesenchymal cells) and can be found throughout the human body. Studies have shown that APs have two prominent roles: identifying and removing dead cells presumably before PPs reach the site of injury and assisting PPs in the removal of cell corpses and the resolution of inflamed tissue. With respect to the engulfment and degradation of dead cells, APs are slower and less efficient than PPs. However, APs are fundamental to preventing the spread of inflammation over a large area. In this review, we present the diversity and characteristics of healthy and non-neoplastic APs in mammals. We also propose a hypothetical mechanism of the efferocytosis of immunoglobulin G (IgG)-opsonized myelin debris by ECs (APs). Furthermore, the ingestion and clearance of dead cells can induce proinflammatory or anti-inflammatory cytokine production, endothelial activation, and cellular fate transition, which contribute to the progression of disease. An understanding of the role of APs is necessary to develop effective intervention strategies, including potential molecular targets for clinical diagnosis and drug development, for inflammation-related diseases.

中文翻译：

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非免疫细胞的意外作用：业余吞噬细胞

死细胞和相关细胞碎片的有效和高效的胞吞作用对于组织稳态和受伤组织的愈合至关重要。以前认为这项重要任务仅限于专业吞噬细胞（PPs）。但是，越来越多的证据表明，吞噬细胞的另一种类型是业余吞噬细胞（AP），也可以参与胞吞作用。AP是非骨髓祖细胞/非免疫细胞，包括分化细胞（例如上皮细胞，成纤维细胞和内皮细胞[EC]）和干细胞（例如神经元祖细胞和间充质细胞），并且可以在整个人体中找到。研究表明，AP具有两个突出的作用：大概在PP到达损伤部位之前识别并清除死细胞，并协助PP清除细胞尸体并消炎。关于死细胞的吞噬和降解，AP比PP慢且效率低。但是，AP对于防止炎症在大范围扩散至关重要。在这篇综述中，我们介绍了哺乳动物中健康和非肿瘤性AP的多样性和特征。我们还提出了由EC（AP）免疫球蛋白G（IgG）调理的髓磷脂碎片的胞吐作用的假想机制。此外，死细胞的摄取和清除可诱导促炎或抗炎细胞因子的产生，内皮细胞的活化和细胞命运的转变，这有助于疾病的发展。