@article {Odackal00481-2020, author = {John Odackal and Victor Yu and Diana Gomez-Manjerres and Joshua J. Field and Marie D. Burdick and Borna Mehrad}, title = {Circulating fibrocytes as prognostic biomarkers of autoimmune interstitial lung disease}, elocation-id = {00481-2020}, year = {2020}, doi = {10.1183/23120541.00481-2020}, publisher = {European Respiratory Society}, abstract = {Background Autoimmunity is a common cause of pulmonary fibrosis and can present either as a manifestation of an established connective tissue disease or as the recently described entity of interstitial pneumonia with autoimmune features. The rate of progression and responsiveness to immunosuppression in these illnesses are difficult to predict. Circulating fibrocytes are bone marrow-derived progenitor cells that home to injured tissues and contribute to lung fibrogenesis. We sought to test the hypothesis that the blood fibrocyte concentration predicts outcome and treatment responsiveness in autoimmune interstitial lung diseases.Methods We compared the concentration of circulating fibrocytes in 50 subjects with autoimmune interstitial lung disease and 26 matched healthy controls and assessed the relationship between serial peripheral blood fibrocyte concentrations and clinical outcomes over a median of 6.25 years.Results As compared to controls, subjects with autoimmune interstitial lung disease had higher circulating concentrations of total fibrocytes, the subset of activated fibrocytes, and fibrocytes with activation of PI3K/AKT/mTOR, TGF-beta receptor, and IL4/IL13 receptor signalling pathways. Over the follow-up period, there were episodes of marked elevation in the concentration of circulating fibrocytes in subjects with autoimmune interstitial lung disease but not controls. Initiation of immunosuppressive therapy was associated with a decline in the concentration of circulating fibrocytes. For each 100 000 cell{\textperiodcentered}mL-1 increase in peak concentration of circulating fibrocytes, we found a 5\% increase in odds of death or lung function decline.Conclusion In patients with autoimmune interstitial lung disease, circulating fibrocytes may represent a biomarker of outcome and treatment response.FootnotesThis manuscript has recently been accepted for publication in the ERJ Open Research. It is published here in its accepted form prior to copyediting and typesetting by our production team. After these production processes are complete and the authors have approved the resulting proofs, the article will move to the latest issue of the ERJOR online. Please open or download the PDF to view this article.Conflict of interest: Dr. Odackal has nothing to disclose.Conflict of interest: Dr. Yu has nothing to disclose.Conflict of interest: Dr. Gomez Manjarres has nothing to disclose.Conflict of interest: Dr. Field has nothing to disclose.Conflict of interest: Dr. Burdick has nothing to disclose.Conflict of interest: Dr. Mehrad holds a patent on the clinical use of fibrocyte measurements in fibrotic interstitial lung diseases.}, URL = {https://openres.ersjournals.com/content/early/2020/09/01/23120541.00481-2020}, eprint = {https://openres.ersjournals.com/content/early/2020/09/01/23120541.00481-2020.full.pdf}, journal = {ERJ Open Research} }