title: Regulatory macrophages induced by infliximab are involved in healing in vivo and in vitro.
abstract: BACKGROUND
  Regulatory macrophages play an important role in wound healing and gut homeostasis and have antiinflammatory properties. Induction of this cell type (Mψ(ind) ) by the anti-tumor necrosis factor (TNF) antibodies, infliximab and adalimumab, has recently been shown in vitro. Also, the superiority of infliximab/azathioprine combination therapy over infliximab or azathioprine monotherapy has recently been established, but the mechanism behind this remains unclear. The aim of this study was to examine the induction of regulatory macrophages in patients with and without mucosal healing in response to infliximab. In addition, we studied the effect of infliximab/azathioprine combination treatment on the differentiation and function of regulatory macrophages.
  
  
  METHODS
  Inflammatory bowel disease (IBD) patients (n = 10) underwent endoscopy before and after first infliximab treatment. Immunohistochemical staining of CD68 and CD206 was performed in all patients. Mixed lymphocyte reactions (MLRs) were treated with infliximab, azathioprine, or both. Macrophage phenotype was evaluated by flow cytometry and inhibition of T-cell proliferation was measured in a secondary MLR containing macrophages and third-party lymphocytes.
  
  
  RESULTS
  A significant induction of regulatory macrophages was observed in patients with mucosal healing after treatment with infliximab; this induction was absent in patients without mucosal healing. In addition, Mψ(ind) have the ability to induce wound healing in an in vitro model, further suggesting a key role for infliximab-induced macrophages in mucosal healing. Upon infliximab/azathioprine combination treatment, an increased number of regulatory macrophages was observed. These macrophages also displayed stronger immunosuppressive properties than macrophages induced by infliximab monotherapy.
  
  
  CONCLUSIONS
  These data show that regulatory macrophages may be involved in mucosal healing and provide a rationale for the superiority of infliximab/azathioprine combination treatment observed in the clinic.
authors.affiliation: Department of Gastroenterology and Hepatology, Leiden University Medical Center, Leiden, the Netherlands. A.C.W.Vos@lumc.nl
authors.forename: Anne Christine W
authors.initials: AC
authors.lastname: Vos
authors.forename: Manon E
authors.initials: ME
authors.lastname: Wildenberg
authors.forename: Ingrid
authors.initials: I
authors.lastname: Arijs
authors.forename: Marjolijn
authors.initials: M
authors.lastname: Duijvestein
authors.forename: Auke P
authors.initials: AP
authors.lastname: Verhaar
authors.forename: Gert
authors.initials: G
authors.lastname: de Hertogh
authors.forename: Séverine
authors.initials: S
authors.lastname: Vermeire
authors.forename: Paul
authors.initials: P
authors.lastname: Rutgeerts
authors.forename: Gijs R
authors.initials: GR
authors.lastname: van den Brink
authors.forename: Daniel W
authors.initials: DW
authors.lastname: Hommes
mesh_terms: D000704:Analysis of Variance; D000893:Anti-Inflammatory Agents / Q000494:pharmacology / Q000627:therapeutic use*; D000911:Antibodies, Monoclonal / Q000494:pharmacology / Q000627:therapeutic use*; D015703:Antigens, CD / Q000378:metabolism; D015214:Antigens, Differentiation, Myelomonocytic / Q000378:metabolism; D001379:Azathioprine / Q000494:pharmacology; D049109:Cell Proliferation / Q000187:drug effects; D002478:Cells, Cultured; D003093:Colitis, Ulcerative / Q000188:drug therapy* / Q000276:immunology / Q000378:metabolism; D003424:Crohn Disease / Q000188:drug therapy* / Q000276:immunology / Q000378:metabolism; D004359:Drug Therapy, Combination; D006801:Humans; D007166:Immunosuppressive Agents / Q000494:pharmacology; D000069285:Infliximab; D007413:Intestinal Mucosa / Q000187:drug effects / Q000378:metabolism; D037181:Lectins, C-Type / Q000378:metabolism; D007959:Lymphocyte Culture Test, Mixed; D008264:Macrophages / Q000187:drug effects / Q000276:immunology*; D000090323:Mannose Receptor; D037241:Mannose-Binding Lectins / Q000378:metabolism; D011956:Receptors, Cell Surface / Q000378:metabolism; D013601:T-Lymphocytes / Q000187:drug effects; D014945:Wound Healing / Q000276:immunology*; D000097382:CD68 Molecule
chemical_list: D000893:Anti-Inflammatory Agents; D000911:Antibodies, Monoclonal; D015703:Antigens, CD; D015214:Antigens, Differentiation, Myelomonocytic; D001379:Azathioprine; D007166:Immunosuppressive Agents; D000069285:Infliximab; D037181:Lectins, C-Type; D000090323:Mannose Receptor; D037241:Mannose-Binding Lectins; D011956:Receptors, Cell Surface; C067980:CD68 antigen, human; D000097382:CD68 Molecule