Regulatory T cells attenuate experimental periodontitis progression in mice Garlet GP, Cardoso CR, Mariano FS, Claudino M, de Assis GF, Campanelli AP, A ´ vila-Campos MJ, Silva JS. Regulatory T cells attenuate experimental periodontitis progression in mice. J Clin Periodontol 2010; 37: 591–600. doi: 10.1111/j.1600- 051X.2010.01586.x. Abstract Aims: The aim of this study was to identify the presence and characterize the function of regulatory T cells (Tregs) in experimental periodontitis in mice. Material and Methods: C57Bl/6 mice infected with Actinobacillus actinomycetemcomitans, treated or not with anti-glucocorticoid-inducible tumour necrosis factor receptor (anti-GITR) to inhibit Tregs function, were analysed regarding inflammatory cell and Tregs influx, alveolar bone loss and cytokine expression/ production (analysed by real-time polymerase chain reaction and ELISA) throughout experimental periodontitis. Results: A. actinomycetemcomitans inoculation in mice resulted in periodontal disease characterized by marked alveolar bone loss and an influx of inflammatory cells. Flow cytometry evaluation of inflammatory cells demonstrated an increased number of CD4 1 CD25 1 and CD4 1 FOXp3 1 cells, characterizing the presence of Tregs in the periodontal environment in a late stage after infection. Tregs-associated cytokines interleukin-10 (IL-10), cytotoxic T lymphocyte-associated molecule 4 (CTLA-4) and transforming growth factor-b (TGF-b) were found to be expressed/produced in a kinetics that resembles Tregs migration. Treatment with anti-GITR, which inhibits Tregs function, showed increased alveolar bone loss and inflammatory cell migration. A reduction in IL- 10, CTLA-4 and TGF-b levels was also observed, while interferon-g, tumour necrosis factor-a and receptor activator for nuclear factor kB ligand levels were increased. However, bacterial load and C-reactive protein serum did not show any differences. Conclusion: Taken together, our results showed that the presence of Treg cells attenuates the severity of experimental periodontitis without impairment in the control of infection. Key words: cytokine; FOXp3; periodontal disease; RANKL; regulatory T cells Accepted for publication 5 April 2010 Periodontal diseases (PDs) are chronic inflammatory diseases characterized by the inflammatory bone resorption of the teeth-supporting structures, being the most prevalent form of bone pathology in humans and a modifying factor of the systemic health of patients (Tonetti & Claffey 2005, Albiger et al. 2007). Inflam- matory immune reactions in response to periodontopathogens are thought to pro- tect the host against the infectious agents, but the persistent release of inflammatory mediators results in the destruction of soft and mineralized periodontal tissues (Eber- sole & Taubman 1994, Gemmell et al. 2001). Inflammatory mediators, such as tumour necrosis factor-a (TNF-a) and interleukin-1b (IL-1b), initiate tissue destruction through the generation of pro- teases that degrade the extracellular matrix, mainly matrix metalloproteinases (MMPs – a family of zinc- and calcium- dependent proteases), and the activation of mechanisms for bone resorption driven by receptor activator for nuclear factor kB ligand (RANKL), which leads to the differentiation and activation of osteo- clasts through binding with receptor activator for nuclear factor kB (RANK) (Taubman et al. 2005, Garlet et al. 2006b). Recently, Th1- and Th17-type cytokines have also been described as Gustavo P. Garlet 1 , Cristina R. Cardoso 2 , Flavia S. Mariano 3 , Marcela Claudino 1 , Gerson F. de Assis 1 , Ana P. Campanelli 1 , Mario J. A ´ vila-Campos 4 and Joa ˜o S. Silva 3 1 Department of Biological Sciences, School of Dentistry of Bauru, Sa ˜o Paulo University – FOB/USP, Sa ˜ o Paulo, Brazil; 2 Department of Biological Sciences, Federal University of Tria ˆngulo Mineiro – UFTM, Uberaba, Minas Gerais, Brazil; 3 Department of Biochemistry and Immunology, School of Medicine of Ribeira ˜o Preto, Sa ˜o Paulo University – FMRP/USP, Sa ˜ o Paulo, Brazil; 4 Department of Microbiology, Institute of Biolomedical Sciences, Sa ˜ o Paulo University – ICB/USP, Sa ˜ o Paulo, Brazil Conflict of interest and source of funding statement The authors declare that they have no conflict of interests. This study was supported by grants from Fundac ¸a ˜o de Amparo a ` Pesquisa do Esta- do de Sa ˜o Paulo – FAPESP (06/00534-1, 07/01705-7). J Clin Periodontol 2010; 37: 591–600 doi: 10.1111/j.1600-051X.2010.01586.x 591 r 2010 John Wiley & Sons A/S