The Modulation of Polymorphonuclear Leukocyte Function by Bacteroides Gingivalis

¹ Department of Periodontics and Endodontics, Faculty of Dentistry, Kyushu University, 1-1-3 Maidashi, Higashi-ku, Fukuoka 812, Japan

Bacteroides gingivalis has been recognized as a pathogen causing adult periodontal disease. In this study, we examined the culture supernatants of B. gingivalis for their ability to alter the function of polymorphonuclear leukocytes (PMNs). After a 60-minute incubation with the culture supernatants of B. gingivalis, it was found that there was a significant reduction of f-methionyl-leucyl-phenylalanine (FMLP) receptor in human and guinea pig PMNs. Superoxide anion (O^-₂) production of PMNs stimulated by FMLP was also suppressed when cells were pre-incubated with the culture supernatants of B. gingivalis. A similar suppression was observed when these cells were stimulated by phorbol myristate acetate. An exohemagglutinin fraction of the culture supernatants showed suppressive activity at a low dose (10 µg/mL). The data presented in this paper suggest that B. gingivalis releases substances which suppress the functions of PMNs via the modulation of cell surface receptors and internal cellular events. These suppressive effects may be important in the pathogenesis of this micro-organism.

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We thank Prof. Toshitaka Koga of the Department of Biochemistry, Kyushu University, Faculty of Dentistry, for his advice in the preparation of this manuscript.