Effect of mixed infection by periodontopathic bacteria-increase of abscess formation on mice and responses by hosts.

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We examined the effect of mixed infection of Porphyromonas gingivalis and Bacteroides forsythus on abscess formation using murine abscess model. When these two bacteria were injected together, they exhibited synergistic effect comparing to the mono-infection by each bacterium. The mutant strains of P. Gingivalis devoid of gingipains exhibited reduced abscess forming abilities comparing to the wild strain. When these mutant strains were used instead of the wild strain in the mixed infection experiments, they only showed additive effects. These results indicate that periodontopathogens exhibit synergism in the periodontal environment and gingipains are playing an important role in the mixed infection.We also examined the effect of P. gingivalis on T cells. The culture supernatant of this bacterium was found to have CD4-cleaving activity. And it was revealed that gingipains were playing an important role in this activity.We also revealed that cytokines, chemokines, and receptors for these are playing an important role in the marginal and periapical periodontitis. They were found to be associated with the progression of periodontitis in Papillon-Leffevre Syndrome, too. We also reported the function of cytokines in the rat experimental periapical periodontitis.