title: The immunohistology of CD40 in human oral epithelium in health and disease.
abstract: BACKGROUND
  CD40 has a role in the regulation of immune responses, cell proliferation and migration, and apoptosis. Little is known of its distribution in oral mucosal pathology.
  
  
  METHODS
  Oral keratinocyte lines were tested for CD40 protein by Western blotting. Immunohistochemistry was used to stain paraffin sections of oral mucosa in health and in inflammatory, reactive, dysplastic and malignant disease.
  
  
  RESULTS
  Western blotting confirmed the presence of CD40 in oral keratinocytes. CD40 was generally expressed by keratinocytes in the basal layer, with variable parabasal expression. Langerhans cells also stained positively. Expression was lost in nine of 33 (27%) epithelial dysplasias, seven of which were severe. Eighty-one percent of well, 69% of moderately and 50% of poorly differentiated oral squamous cell carcinomas (OSCC) expressed CD40. Overall, 45 of 65 (69%) OSCC were positive. The pattern of expression was unrelated to tumour differentiation.
  
  
  CONCLUSIONS
  CD40 expression by basal and parabasal oral keratinocytes is physiological. Expression is lost in approximately one-third of oral epithelial dysplasias and OSCC. The significance of such loss remains unknown, but may be related to immunological or other abnormalities of keratinocyte homeostasis.
authors.affiliation: Oral and Maxillofacial Pathology Unit, Eastman Dental Institute for Oral Healthcare Sciences, University College London, London WC1X 8LD, UK.
authors.forename: Mariana
authors.initials: M
authors.lastname: Villarroel Dorrego
authors.forename: Paul M
authors.initials: PM
authors.lastname: Speight
authors.forename: A William
authors.initials: AW
authors.lastname: Barrett
mesh_terms: D015153:Blotting, Western; D019013:CD40 Antigens / Q000032:analysis / Q000276:immunology*; D002294:Carcinoma, Squamous Cell / Q000276:immunology*; D002460:Cell Line; D045744:Cell Line, Tumor; D006801:Humans; D007124:Immunoenzyme Techniques; D015603:Keratinocytes / Q000276:immunology*; D009061:Mouth Mucosa / Q000276:immunology*; D009062:Mouth Neoplasms / Q000276:immunology*
chemical_list: D019013:CD40 Antigens