title: Granulocyte Macrophage Colony-Stimulating Factor-Activated CD39+/CD73+Murine Monocytes Modulate Intestinal Inflammation via Induction of Regulatory T Cells.
abstract: OBJECTIVE
  Granulocyte macrophage colony-stimulating factor (GM-CSF) treatment induces clinical response in patients with active Crohn's disease. To explore whether monocytes mediate GM-CSF effects in vivo, we used a mouse model of chronic colitis induced by dextran sulfate sodium (DSS).
  
  
  METHODS
  Murine bone marrow-derived monocytes were activated with GM-CSF in vitro, and gene expression, phenotype, and function of GM-CSF-activated monocytes (GMaM) were analyzed. Therapeutic effects of GMaM were assessed in a model of chronic colitis induced by repeated cycles of DSS. Monocytes were administered intravenously and their immunomodulatory functions were evaluated in vivo by clinical monitoring, histology, endoscopy, immunohistochemistry, and expression of inflammatory markers in the colon. The distribution of injected monocytes in the intestine was measured by in vivo imaging.
  
  
  RESULTS
  GMaM expressed significantly higher levels of anti-inflammatory molecules. Production of reactive oxygen species was also increased while phagocytosis and adherence were decreased. GMaM up-regulated CD39 and CD73, which allows the conversion of adenosine triphosphate into adenosine and coincided with the induction of Foxp3+(forkhead-box-protein P3 positive) regulatory T cells (Treg) in cocultures of GMaM and naive T cells. In chronic DSS-induced colitis, adoptive transfer of GMaM led to significant clinical improvement, as demonstrated by reduced weight loss, inflammatory infiltration, ulceration, and colon shrinkage. As GMaM migrated faster and persisted longer in the inflamed intestine compared with control monocytes, their presence induced Treg generation in vivo.
  
  
  CONCLUSIONS
  GM-CSF leads to specific monocyte activation that modulates experimental colitis via mechanisms that include the induction of Treg. We demonstrate a possible mechanism of Treg induction through CD39 and CD73 expression on monocytes.
authors.affiliation: Department of Pediatric Rheumatology and Immunology, University Children's Hospital Münster, Münster, Germany.
authors.forename: Toni
authors.initials: T
authors.lastname: Weinhage
authors.affiliation: Department of Pediatric Rheumatology and Immunology, University Children's Hospital Münster, Münster, Germany; The Royal Children's Hospital Melbourne, Murdoch Children's Research Institute, Gastrointestinal Research in Inflammation and Pathology, Parkville, Australia; Interdisciplinary Centre of Clinical Research, University of Münster, Münster, Germany; Department of Pediatrics, University of Melbourne, Melbourne Medical School, Parkville, Australia.
authors.forename: Jan
authors.initials: J
authors.lastname: Däbritz
authors.affiliation: Department of Translational Dermatoinfectiology, University of Münster, Münster, Germany.
authors.forename: Anne
authors.initials: A
authors.lastname: Brockhausen
authors.affiliation: Department of Pediatric Rheumatology and Immunology, University Children's Hospital Münster, Münster, Germany.
authors.forename: Timo
authors.initials: T
authors.lastname: Wirth
authors.affiliation: Department of Pediatric Rheumatology and Immunology, University Children's Hospital Münster, Münster, Germany; Department of Medicine B, University Hospital Münster, Münster, Germany.
authors.forename: Markus
authors.initials: M
authors.lastname: Brückner
authors.affiliation: Department of Pediatric Rheumatology and Immunology, University Children's Hospital Münster, Münster, Germany; Department of Dermatology, University Hospital Münster, Münster, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Belz
authors.affiliation: Department of Pediatric Rheumatology and Immunology, University Children's Hospital Münster, Münster, Germany; Interdisciplinary Centre of Clinical Research, University of Münster, Münster, Germany.
authors.forename: Dirk
authors.initials: D
authors.lastname: Foell
authors.affiliation: Department of Pediatric Rheumatology and Immunology, University Children's Hospital Münster, Münster, Germany.
authors.forename: Georg
authors.initials: G
authors.lastname: Varga
keywords: ALDH, aldehyde dehydrogenase; ATP, adenosine triphosphate; Adaptive Immunity; Arg1, arginase 1; CD, Crohn’s disease; CD39, E-NTPDase; CD73, ecto-5′-nucleotidase; CFSE, carboxyfluorescein succinimidyl ester; DC, dendritic cells; DSS, dextran sulfate sodium; Dextran Sulfate Sodium; Experimental Colitis; FCS, fetal calf serum; Foxp3, forkhead-box-protein P3; GM-CSF; GM-CSF, granulocyte macrophage colony-stimulating factor; GMaM, granulocyte-macrophage colony-stimulating factor–activated monocytes; IBD, inflammatory bowel disease; IL, interleukin; IL-1Ra, IL-1 receptor antagonist; Immune Response; Innate Immunity; LPS, lipopolysaccharide; MACS, magnetic-activated cell sorting; MEICS, murine endoscopic index of colitis severity; Monocyte; NO, nitric oxide; OD, optical density; PBS, phosphate-buffered saline; PCR, polymerase chain reaction; RA, retinoic acid; ROS, reactive oxygen species; T Cell; TNFα, tumor necrosis factor α; Treg, regulatory T cells; WT, wild type; qRT-PCR, quantitative reverse-transcription polymerase chain reaction