The Role of Innate T Cells in Oral Bacterial Infection

Chronic periodontitis is an inflammatory disease of the supporting tissues of teeth and if left untreated will result to bone resorption and eventual tooth loss. The subgingival plaque bacteria Porphyromonas gingivalis, Treponema denticola and Tannerella forsythia have been closely associated with chronic periodontitis. Preliminary biochemical studies in our laboratory have shown that P. gingivalis has a major glycolipid and T. forsythia has three major glycolipids which can stimulate NKT cells. In addition, γδ T cells were shown to contribute to bone loss in the mouse periodontal model. Objectives: The role of these early innate T cells in oral bacterial infection was investigated using established methods of the abscess model and periodontitis model with P. gingivalis 33277 or W50, respectively. Methods: NKT cells and γδ T cells isolated from the spleen and thymus were analysed for the cell surface activation marker, CD69 and absolute numbers were calculated. Cytokine production from these cells was measured using the Bio-Plex® system. Results: NKT cells and γδ T cells were highly activated within 7 to 9 days of infection and cell numbers were increased within specific tissue sites. NKT cells were shown to produce high levels of IL-17 in response to incubation with P. gingivalis W50. Further, naïve γδ T cells have been shown to phagocytose P. gingivalis and that P. gingivalis-activated γδ T cells enhanced this phagocytosis. Conclusion: Understanding the functional roles of these early innate cells in response to oral bacteria and their bacterial products such as glycolipids and lipopolysaccharides, may aid in the development of therapeutics to induce a favorable outcome in Chronic Periodontitis.