Identification of IL-17⁺FOXP3⁺ T cells in periodontitis lesions

Methods: We analyzed the characteristics of gingival and peripheral blood CD4⁺ T-cell lines established from nine patients with chronic periodontitis. In addition, we obtained gingival biopsies from another ten patients and immunohistochemically characterized infiltrating cells.

Results: The proportion of Tregs (IL-17A^-FOXP3⁺ cells) was significantly lower but the proportion of Th17 cells (IL-17A⁺FOXP3^- cells) was tended to be higher in gingival CD4⁺ T-cell lines than in peripheral blood CD4⁺ T-cell lines. The ratio of IL-17A⁺FOXP3⁺ cells to total FOXP3⁺ cells was significantly higher in gingival CD4⁺ T-cell lines than in peripheral blood CD4⁺ T-cell lines. Immunohistochemical analysis revealed that, in addition to Tregs and Th17 cells, IL-17⁺FOXP3⁺ cells were identified in periodontitis lesions.

Conclusion: This study identified for the first time the infiltration of IL-17⁺FOXP3⁺ T cells in periodontitis lesions. These data suggest that an in vivo conversion of Tregs to Th17 cells may be associated with the pathogenesis of periodontitis.