title: Regulatory T cells in mouse periapical lesions.
abstract: BACKGROUND
  T-regulatory (Treg, CD4+ FOXP3+) cells constitute a unique subpopulation of CD4+ T cells that inhibit T-cell responses and prevent disease development/exacerbation in models of autoimmunity. In the present study, we tested the hypothesis that Treg cells are induced in periapical lesions by dental pulp infection.
  
  
  METHODS
  In situ hybridization (ISH) was used to localize FOXP3+ cells on day 21 after pulp exposure of the first molar teeth and infection with bacteria from the oral environment. FOXP3/GFP knock-in transgenic mice were used to quantify FOXP3+ Treg cells that infiltrate into periapical lesions by flow cytometry on days 7, 14, and 21 after infection. Periodontal ligament from uninfected teeth served as a negative control.
  
  
  RESULTS
  ISH showed strong signals that showed the presence of FOXP3+ cells mainly at the periphery of periapical lesions. In contrast, no positive cells were present in the periodontal ligament of uninfected controls. Flow cytometry showed an increase in the number of FOXP3+ Treg beginning between day 7 and day 14 (0.69% of the infiltrate) after infection and increased to day 21 (0.94%) (p < 0.05 and p < 0.001, respectively, vs uninfected controls). Treg were also increased in number in draining cervical lymph nodes after pulpal infection.
  
  
  CONCLUSIONS
  These results show that Treg cells are induced to infiltrate into periapical lesions by pulpal infection and suggest that they increase in a time-dependent manner.
authors.affiliation: Department of Restorative Dentistry and Biomaterials Sciences, Harvard School of Dental Medicine, Boston, MA, USA.
authors.forename: Emad
authors.initials: E
authors.lastname: AlShwaimi
authors.forename: Patricia
authors.initials: P
authors.lastname: Purcell
authors.forename: Toshihisa
authors.initials: T
authors.lastname: Kawai
authors.forename: Hajime
authors.initials: H
authors.lastname: Sasaki
authors.forename: Mohamed
authors.initials: M
authors.lastname: Oukka
authors.forename: Antonio
authors.initials: A
authors.lastname: Campos-Neto
authors.forename: Philip
authors.initials: P
authors.lastname: Stashenko
mesh_terms: D000818:Animals; D003789:Dental Pulp Exposure / Q000276:immunology; D005434:Flow Cytometry; D051858:Forkhead Transcription Factors / Q000235:genetics; D055879:Gene Knock-In Techniques; D017403:In Situ Hybridization; D008198:Lymph Nodes / Q000276:immunology; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D009333:Neck; D010485:Periapical Periodontitis / Q000276:immunology*; D013047:Specific Pathogen-Free Organisms; D050378:T-Lymphocytes, Regulatory / Q000276:immunology*
chemical_list: D051858:Forkhead Transcription Factors; C498833:Foxp3 protein, mouse