title: Aberrant function of myeloid-derived suppressor cells (MDSCs) in experimental colitis and in inflammatory bowel disease (IBD) immune responses.
abstract: OBJECTIVE
  Myeloid-derived suppressor cells (MDSCs) encompass a novel population of suppressor cells and a potential candidate for cell-based therapies in inflammatory diseases. Herein, we investigated their immunomodulatory properties in experimental inflammatory colitis and T cell-mediated immune responses in inflammatory bowel disease (IBD) patients.
  
  
  METHODS
  MDSCs (defined as CD14-HLA-DR-/lowCD33+CD15+) numbers were determined in peripheral blood (PB) from IBD patients. PB MDSC function was assessed in vitro. Experimental colitis was induced upon 2,4,6-trinitrobenzene sulfonic acid (TNBS) treatment and MDSCs were characterized by flow cytometry. The in vivo suppressive potential of bone marrow (BM)-derived MDSCs (BM-MDSCs) was tested by using both depleting and adoptive transfer strategies.
  
  
  RESULTS
  MDSCs were enriched in the periphery of IBD patients during active disease. TNBS colitis induced amplification of MDSCs, particularly of the granulocytic (Ly6G+) subset during the effector phase of disease. Of interest, BM-MDSCs potently suppressed CD4+T cell responses under steady state but failed to control colitis-associated immune responses in vivo. Mechanistically, under the colonic inflammatory milieu MDSCs switched phenotype (decreased proportion of Gr1highand increased numbers of Gr1low) and downregulated CCAAT/enhancer-binding protein beta (CEBPβ) expression, a critical transcription factor for the suppressive function of MDSCs. In accordance with the murine data, human CD33+CD15+MDSCs from peripheral blood of IBD patients not only failed to suppress autologous T cell responses but instead enhanced T cell proliferation in vitro.
  
  
  CONCLUSIONS
  Our findings demonstrate an aberrant function of MDSCs in experimental inflammatory colitis and in IBD-associated immune responses in vitro. Delineation of the mechanisms that underlie the loss of MDSCs function in IBD may provide novel therapeutic targets.
authors.affiliation: a Laboratory of Autoimmunity and Inflammation , University of Crete Medical School, and Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology , Heraklion , Greece.
authors.forename: Eleni
authors.initials: E
authors.lastname: Kontaki
authors.affiliation: a Laboratory of Autoimmunity and Inflammation , University of Crete Medical School, and Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology , Heraklion , Greece.
authors.forename: Dimitrios T
authors.initials: DT
authors.lastname: Boumpas
authors.affiliation: b Laboratory of Cytopathology , University of Crete Medical School , Heraklion , Greece.
authors.forename: Maria
authors.initials: M
authors.lastname: Tzardi
authors.affiliation: c Division of Gastroenterology , University of Crete Medical School , Heraklion , Greece , and.
authors.forename: Ioannis A
authors.initials: IA
authors.lastname: Mouzas
authors.affiliation: c Division of Gastroenterology , University of Crete Medical School , Heraklion , Greece , and.
authors.forename: Konstantinos A
authors.initials: KA
authors.lastname: Papadakis
authors.affiliation: d Division of Clinical , Experimental Surgery, & Translational Research, Biomedical Research Foundation of the Academy of Athens , Athens , Greece.
authors.forename: Panayotis
authors.initials: P
authors.lastname: Verginis
mesh_terms: D000818:Animals; D015703:Antigens, CD / Q000378:metabolism; D015415:Biomarkers; D022782:CCAAT-Enhancer-Binding Protein-beta / Q000378:metabolism; D060833:Cellular Microenvironment / Q000276:immunology; D003092:Colitis / Q000276:immunology* / Q000378:metabolism* / Q000473:pathology; D016207:Cytokines / Q000378:metabolism; D004195:Disease Models, Animal; D005260:Female; D006801:Humans; D056747:Immunomodulation; D016130:Immunophenotyping; D015212:Inflammatory Bowel Diseases / Q000276:immunology* / Q000378:metabolism* / Q000473:pathology; D008213:Lymphocyte Activation / Q000276:immunology; D051379:Mice; D000072737:Myeloid-Derived Suppressor Cells / Q000276:immunology* / Q000378:metabolism*; D016176:T-Lymphocyte Subsets / Q000276:immunology / Q000378:metabolism
chemical_list: D015703:Antigens, CD; D015415:Biomarkers; D022782:CCAAT-Enhancer-Binding Protein-beta; D016207:Cytokines
keywords: BM-MDSCs; CEBPβ; IBD; MDSCs; experimental colitis