RT Journal Article SR Electronic T1 CX3CR1–fractalkine axis drives kinetic changes of monocytes in fibrotic interstitial lung diseases JF European Respiratory Journal JO Eur Respir J FD European Respiratory Society SP 1900460 DO 10.1183/13993003.00460-2019 VO 55 IS 2 A1 Flavia R. Greiffo A1 Valeria Viteri-Alvarez A1 Marion Frankenberger A1 Daniela Dietel A1 Almudena Ortega-Gomez A1 Joyce S. Lee A1 Anne Hilgendorff A1 Jürgen Behr A1 Oliver Soehnlein A1 Oliver Eickelberg A1 Isis E. Fernandez YR 2020 UL http://erj.ersjournals.com/content/55/2/1900460.abstract AB 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