title: Mechanical removal of dendritic cell-generating non-classical monocytes via ex vivo lung perfusion.
abstract: BACKGROUND
  Ex vivo lung perfusion (EVLP) is a novel procedure designed to rapidly assess and recondition unusable donor lungs for transplantation (LTx). EVLP may reduce graft immunogenicity and allorecognition via removal of passenger leukocytes. We aimed to explore this hypothesis using human EVLP and in vitro analysis.
  
  
  METHODS
  Explanted human lungs (n = 7) underwent standard EVLP. Perfusate samples and the leukocyte filter were collected, and cells characterized via flow cytometry. Isolated alveolar monocytes (from post-LTx bronchoalveolar lavage) were differentiated to dendritic cells and characterized (n = 10). An in vitro (air epithelial-liquid endothelial) lung model was utilized to evaluate monocyte migration and differentiation within the lung.
  
  
  RESULTS
  Non-classical monocytes (NCM, normally <1% of total white blood cell repertoire) mobilized within 30 minutes of EVLP and represented 80.04% of the passenger leukocyte population. This subset readily differentiated to dendritic cells and secreted pro-inflammatory cytokines (interferon-γ and interleukin-2) after stimulation. NCM rapidly diapedesed from the vascular bed to the alveolus and, when cultured on the alveolus, differentiated to dendritic cells with inflammatory phenotypes.
  
  
  CONCLUSIONS
  The lung possesses a reservoir of NCM, which can readily diapedese to the alveolus or mobilize in the circulation. After activation, NCM differentiate to inflammatory dendritic cells with T-cell co-stimulatory capacity. EVLP may impart additional benefits after LTx via the removal of passenger monocytes, which may represent a previously unidentified beneficial mechanism of action.
authors: Transplant Centre, University Hospital of South Manchester; Manchester Collaborative Centre for Inflammation Research, Core Technology Facility, Institute of Inflammation and Repair, University of Manchester, Manchester, UK.
authors: John P
authors: JP
authors: Stone
authors: Transplant Centre, University Hospital of South Manchester.
authors: Hannah
authors: H
authors: Sevenoaks
authors: Department of Cardiothoracic Surgery, Lund University and Skåne University Hospital, Lund, Sweden.
authors: Trygve
authors: T
authors: Sjöberg
authors: Department of Cardiothoracic Surgery, Lund University and Skåne University Hospital, Lund, Sweden.
authors: Stig
authors: S
authors: Steen
authors: Transplant Centre, University Hospital of South Manchester; Manchester Collaborative Centre for Inflammation Research, Core Technology Facility, Institute of Inflammation and Repair, University of Manchester, Manchester, UK.
authors: Nizar
authors: N
authors: Yonan
authors: Transplant Centre, University Hospital of South Manchester; Manchester Collaborative Centre for Inflammation Research, Core Technology Facility, Institute of Inflammation and Repair, University of Manchester, Manchester, UK. Electronic address: james.fildes@manchester.ac.uk.
authors: James E
authors: JE
authors: Fildes
mesh_terms: D018893:Bronchoalveolar Lavage; D002454:Cell Differentiation; D002465:Cell Movement; D002469:Cell Separation / Q000379:methods*; D003713:Dendritic Cells / Q000166:cytology*; D005434:Flow Cytometry; D006801:Humans; D066298:In Vitro Techniques; D008168:Lung / Q000166:cytology*; D016040:Lung Transplantation; D009000:Monocytes / Q000166:cytology*; D010477:Perfusion / Q000379:methods*; D013314:Stress, Mechanical
keywords: dendritic cell; diapedesis; ex vivo lung perfusion; lung transplantation; monocyte; non-classical monocyte; passenger leukocytes