Objective: Porphyromonas gingivalis can invade and survive within its host epithelial cells. The aim of this study was to test our hypothesis that persistent presence of intracellular periodontal pathogens in gingival tissue causes the chronic inflammation and that an inappropriate immune response is a risk factor for periodontitis.
Methods: Together with the presence of P. gingivalis, the distribution of B cells, plasma cells, and CD4(+), CD8(+), and FOXP3(+) regulatory T cells was evaluated in gingival tissues from healthy (n = 7) and periodontitis (n = 8) sites by in situ hybridization and immunohistochemistry, respectively.
Results: Porphyromonas gingivalis was detected in proximity to inflammatory infiltrates in three and seven biopsies from the healthy and periodontitis sites, respectively. Compared with healthy sites, periodontal lesions contained a significantly increased number of each immune cell studied with a relative dominance of plasma cells over T cells.
Conclusions: Persistent bacterial invasion of gingival tissues in combination with a plasma cell-dominant immune response may be involved in the pathogenesis of periodontitis.