title: Recurrent aphthous ulcers--a Toll-like receptor-mediated disease?
abstract: BACKGROUND
  Recurrent aphthous ulcer (RAU) is characterized by acute and painful inflammatory ulcerations, which heal spontaneously but tend to recur. Many pathogens have been proposed as causative agents, but none has been consistently proven. According to our hypothesis, RAU is an autoinflammatory disorder triggered by pathogen-associated molecular patterns (PAMPs) shared by different pathogenic and commensal microbes.
  
  
  METHODS
  PAMP-reactive Toll-like receptors (TLRs) were mapped in oral epithelium in healthy controls compared to RAU.
  
  
  RESULTS
  In controls, the superficial epithelium formed a TLR(-), a PAMP non-reactive physical barrier zone, but all TLRs were found deeper in the epithelium, usually restricted to suprabasal and basal cell layers. In RAU, the epithelial TLR polarity was lost: TLRs 1, 2, 5, 7, and 8 were found throughout the epithelium, but also TLRs 4, 6, and 10 extended higher up than normally, whereas TLR-3 was almost lost in RAU. In RAU lesions, connective tissue stroma was heavily infiltrated by TLR(+) inflammatory cells.
  
  
  CONCLUSIONS
  Normal TLR architecture prevents inflammatory responses against normal microbes but still contains a deep TLR(+) , PAMP-reactive dormant defense zone. In RAU, the TLR(+), PAMP-reactive zone extends to surface or subsurface exposed to microbial PAMPs. TLR reactivity is further enhanced by recruitment of inflammatory leukocytes forming a new deep line of defense. The organization of the TLR system in healthy mucosa and its changes in RAU are compatible with active pathogenic involvement of TLRs, which together with the typical clinical picture and course suggest that RAU is a TLR-mediated disease.
authors: Department of Oral Pathology, Institute of Dentistry, University of Helsinki, Helsinki, Finland.
authors: Jarkko
authors: J
authors: Hietanen
authors: Ritva
authors: R
authors: Häyrinen-Immonen
authors: Ahmed
authors: A
authors: Al-Samadi
authors: Nina
authors: N
authors: Trokovic
authors: Katja
authors: K
authors: Koskenpato
authors: Yrjö T
authors: YT
authors: Konttinen
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D001327:Autoimmune Diseases / Q000276:immunology; D016764:Cell Polarity / Q000276:immunology; D002648:Child; D004847:Epithelial Cells / Q000276:immunology; D004848:Epithelium / Q000276:immunology; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D007249:Inflammation; D008297:Male; D008875:Middle Aged; D009061:Mouth Mucosa / Q000276:immunology; D012008:Recurrence; D013281:Stomatitis, Aphthous / Q000276:immunology*; D051194:Toll-Like Receptor 1; D051201:Toll-Like Receptor 10 / Q000032:analysis; D051195:Toll-Like Receptor 2 / Q000032:analysis; D051196:Toll-Like Receptor 3 / Q000032:analysis; D051197:Toll-Like Receptor 4 / Q000032:analysis; D051198:Toll-Like Receptor 5 / Q000032:analysis; D051216:Toll-Like Receptor 6 / Q000032:analysis; D051199:Toll-Like Receptor 7 / Q000032:analysis; D051200:Toll-Like Receptor 8 / Q000032:analysis; D051193:Toll-Like Receptors / Q000276:immunology*; D055815:Young Adult
chemical_list: C475955:TLR10 protein, human; C495342:TLR2 protein, human; C495344:TLR3 protein, human; C495345:TLR4 protein, human; C495346:TLR5 protein, human; C495368:TLR6 protein, human; C495348:TLR7 protein, human; C495349:TLR8 protein, human; D051194:Toll-Like Receptor 1; D051201:Toll-Like Receptor 10; D051195:Toll-Like Receptor 2; D051196:Toll-Like Receptor 3; D051197:Toll-Like Receptor 4; D051198:Toll-Like Receptor 5; D051216:Toll-Like Receptor 6; D051199:Toll-Like Receptor 7; D051200:Toll-Like Receptor 8; D051193:Toll-Like Receptors