Circulating immune cell populations have been shown to contribute to interstitial lung disease (ILD). In this study, we analysed circulating and lung resident monocyte populations, and assessed their phenotype and recruitment from the blood to the lung in ILD. Flow cytometry analysis of blood samples for quantifying circulating monocytes was performed in 105 subjects: 83 with ILD (n=36, n=28 and n=19 for nonspecific interstitial pneumonia, hypersensitivity pneumonitis and connective-tissue disease-associated ILD, respectively), as well as 22 controls. Monocyte localisation and abundance were assessed using immunofluorescence and flow cytometry of lung tissue. Monocyte populations were cultured either alone or with endothelial cells to assess fractalkine-dependent transmigration pattern. We show that circulating classical monocytes (CM) were increased in ILD compared with controls, while nonclassical monocytes (NCM) were decreased. CM abundance correlated inversely with lung function, while NCM abundance correlated positively. Both CCL2 and CX3CL1 concentrations were increased in plasma and lungs of ILD patients. Fractalkine co-localised with ciliated bronchial epithelial cells, thereby creating a chemoattractant gradient towards the lung. Fractalkine enhanced endothelial transmigration of NCM in ILD samples only. Immunofluorescence, as well as flow cytometry, showed an increased presence of NCM in fibrotic niches in ILD lungs. Moreover, NCM in the ILD lungs expressed increased CX3CR1, M2-like and phagocytic markers. Taken together, our data support that in ILD, fractalkine drives the migration of CX3CR1+ NCM to the lungs, thereby perpetuating the local fibrotic process. The compartmental imbalance of fractalkine mediates the migration of nonclassical monocytes into fibrotic lung tissues. Furthermore, nonclassical monocyte-derived cells show a M2-like and phagocytic phenotype in ILD lungs. http://bit.ly/2CMFWex

中文翻译：

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CX3CR1-fractalkine 轴驱动纤维化间质性肺病中单核细胞的动力学变化

循环免疫细胞群已被证明会导致间质性肺病 (ILD)。在这项研究中，我们分析了循环和肺常驻单核细胞群，并评估了它们的表型和 ILD 中从血液到肺的募集。在 105 名受试者中进行了用于定量循环单核细胞的血液样本的流式细胞术分析：83 名患有 ILD（分别为 n=36、n=28 和 n=19，分别为非特异性间质性肺炎、过敏性肺炎和结缔组织病相关的 ILD），以及 22 个控件。使用免疫荧光和肺组织流式细胞术评估单核细胞定位和丰度。单核细胞群被单独培养或与内皮细胞一起培养，以评估 fractalkine 依赖的轮回模式。我们表明，与对照相比，ILD 中循环经典单核细胞 (CM) 增加，而非经典单核细胞 (NCM) 减少。CM 丰度与肺功能呈负相关，而 NCM 丰度呈正相关。ILD 患者血浆和肺​​中的 CCL2 和 CX3CL1 浓度均增加。Fractalkine 与纤毛支气管上皮细胞共定位，从而产生朝向肺的化学引诱梯度。Fractalkine 仅增强了 ILD 样品中 NCM 的内皮迁移。免疫荧光以及流式细胞术显示 ILD 肺纤维化壁龛中 NCM 的存在增加。此外，ILD 肺中的 NCM 表达增加的 CX3CR1、M2 样和吞噬标志物。总之，我们的数据支持在 ILD 中，fractalkine 驱动 CX3CR1+ NCM 迁移到肺部，从而使局部纤维化过程永久化。fractalkine 的区室失衡介导了非经典单核细胞向纤维化肺组织的迁移。此外，非经典的单核细胞衍生细胞在 ILD 肺中显示出 M2 样和吞噬细胞表型。http://bit.ly/2CMFWex