The induction of polyclonal B-cell activation and interleukin-1 production by the 75-kDa cell surface protein from Porphyromonas gingivalis in mice

The immunobiological activities of 75-kDa protein, fimbrial protein and lipopolysaccharide lipopolysaccharide prepared from whole cells of Porphyromonas gingivalis 381 were compared. The 75-kDa protein was mitogenic for BALB/c nu/nu, BALB/c and lipopolysaccharide-responsive C3H/HeN mouse spleen cells and for lipopolysaccharide-non-responsive C3H/HeJ mouse spleen cells. The response was significant in BALB/c mouse spleen cells incubated with 1-100 micrograms/ml of the 75-kDa protein. Furthermore, the 75-kDa protein exhibited polyclonal B-cell activation in murine spleen cells, which was similar to the lipopolysaccharide of P. gingivalis. In contrast, fimbriae from P. gingivalis did not, or only weakly, activated murine spleen cells. C3H/HeN mouse macrophages exposed to 10 micrograms/ml of the 75-kDa protein released large amounts of interleukin-1 (IL-1), which were maximal for 48 h, whereas IL-6 activity in macrophage supernatants was not detected throughout the culture period. These results suggest that the 75-kDa protein is a potent polyclonal B-cell activator and that it stimulates IL-1 production from murine peritoneal macrophages as well as lipopolysaccharide, which may play an important part in the inflammatory response during the development of periodontal diseases.