Pulmonary fibrosis is a disease in which excessive extracellular matrix (ECM) accumulation occurs in the lungs, which induces thickening of the alveolar walls, ultimately leading to the destruction of alveolar structures and respiratory failure. Idiopathic pulmonary fibrosis, the cause of which is unknown, has a poor prognosis with a median survival of 2–4 years after diagnosis. There is currently no known curative treatment. The mechanism underlying pulmonary fibrosis is thought to be initiated by the dysfunction of type II alveolar epithelial cells, which leads to ECM overproduction through the activation of fibroblasts. In addition, it has been suggested that a variety of cells contribute to fibrotic processes. In particular, clinical and basic research findings examining the roles of macrophages suggest that they may be pivotal regulators of pulmonary fibrosis. In this review, we discuss the characteristics, functions and origins of subsets of macrophages involved in pulmonary fibrosis, including resident alveolar, interstitial and monocyte-derived macrophages.

中文翻译：

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肺纤维化中的巨噬细胞

肺纤维化是一种肺部细胞外基质（ECM）过度积累，导致肺泡壁增厚，最终导致肺泡结构破坏和呼吸衰竭的疾病。特发性肺纤维化，病因不明，预后不良，诊断后中位生存期为 2-4 年。目前没有已知的治疗方法。肺纤维化的潜在机制被认为是由 II 型肺泡上皮细胞功能障碍引发的，这通过激活成纤维细胞导致 ECM 过度生产。此外，已经提出多种细胞有助于纤维化过程。特别是，检查巨噬细胞作用的临床和基础研究结果表明，它们可能是肺纤维化的关键调节因子。在这篇综述中，我们讨论了参与肺纤维化的巨噬细胞亚群的特征、功能和起源，包括常驻肺泡、间质和单核细胞衍生的巨噬细胞。