title: The number of immune cells is lower in healthy oral mucosa compared to skin and does not increase after scarring.
abstract: OBJECTIVE
  Depending on the location of injury, wounds can heal with different outcomes. In addition foetal wounds heal fast without scar formation, while scars are a common feature of regular skin repair. Since inflammation is very limited in these wounds reduced numbers or even absence of immune cells might be responsible for scarless foetal wound healing. It is thought that various immune cells, such as macrophages, neutrophils and T-cells, play a role in aberrant wound healing and the fibrotic process seen in scar formation in the adult skin. Similar to the foetus, oral wounds show comparable healing properties by means of accelerated reepithelialization and negligible scar formation. It is possible that reduced inflammatory reaction as a result of lower numbers of immune cells are present in oral wounds compared to skin wounds.
  
  
  METHODS
  Here we investigated the presence of various immune cells in human skin and oral mucosa, with or without scars. The presence or absence of these cells may play a role in the different modes of healing observed between the two types of tissue. Mast cells, neutrophils, M1/M2 macrophages, T-cells and blood vessels were localized in healthy and scarred skin and oral mucosa (scars>1 year old).
  
  
  RESULTS
  Oral mucosa had significantly fewer neutrophils, macrophages, mannose receptor-positive M2 macrophages, but more blood vessels. Scars contained similar numbers of immune cells compared to healthy tissues.
  
  
  CONCLUSIONS
  Less immune cells in the healthy oral mucosa may induce a diminished immune reaction when wounding occurs, and could explain the better healing capacity of the oral mucosa.
authors.affiliation: Department of Molecular Cell Biology & Immunology, VU University Medical Center, Amsterdam, The Netherlands; Department of Plastic and Reconstructive Surgery, VU University Medical Center, Amsterdam, The Netherlands. Electronic address: je.glim@vumc.nl.
authors.forename: Judith E
authors.initials: JE
authors.lastname: Glim
authors.affiliation: Department of Molecular Cell Biology & Immunology, VU University Medical Center, Amsterdam, The Netherlands.
authors.forename: Robert H J
authors.initials: RH
authors.lastname: Beelen
authors.affiliation: Department of Plastic and Reconstructive Surgery, VU University Medical Center, Amsterdam, The Netherlands.
authors.forename: Frank B
authors.initials: FB
authors.lastname: Niessen
authors.affiliation: Department of Oral Cell Biology, Academic Centre for Dentistry (ACTA), University of Amsterdam and VU University Amsterdam, MOVE Research Institute, Amsterdam, The Netherlands.
authors.forename: Vincent
authors.initials: V
authors.lastname: Everts
authors.affiliation: Department of Molecular Cell Biology & Immunology, VU University Medical Center, Amsterdam, The Netherlands; Association of Dutch Burn Centres, Beverwijk, The Netherlands.
authors.forename: Magda M W
authors.initials: MM
authors.lastname: Ulrich
mesh_terms: D000293:Adolescent; D000328:Adult; D002648:Child; D002675:Child, Preschool; D002921:Cicatrix / Q000276:immunology*; D005260:Female; D006801:Humans; D008264:Macrophages / Q000276:immunology; D008297:Male; D008407:Mast Cells / Q000276:immunology; D008875:Middle Aged; D009061:Mouth Mucosa / Q000098:blood supply / Q000166:cytology*; D009504:Neutrophils / Q000276:immunology; D012867:Skin / Q000098:blood supply / Q000166:cytology*; D013601:T-Lymphocytes / Q000276:immunology
keywords: Fibrosis; Immune cells; Scars; Wound healing