Induction of anti-thymocyte/T lymphocyte antibodies in mice injected with lipopolysaccharides from periodontopathic bacteria.

We examined the levels of anti-thymocyte/T lymphocyte autoantibody (ATA) in the serum of mice injected intraperitoneally with lipopolysaccharides (LPS) from periodontopathic bacteria; Porphyromonas gingivalis, Actinobacillus actinomycetemcomitans, Fusobacterium nucleatum, Capnocytophaga ochracea, and non-oral Escherichia coli. All of the LPS induced IgM-ATA. Among these, LPS from C. ochracea induced the highest level of IgM-ATA, whereas that of P. gingivalis induced the lowest. The peritoneal T lymphocytes of mice injected with LPS were bound by IgM-ATA. Peritoneal B-1 (CD5+B) cells stimulated by each LPS produced much more IgM-ATA than splenic B-2 (CD5-B) cells, suggesting that B-1 cells might be responsible for the production of these antibodies. Serum of mice injected with C. ochracea and F. nucleatum LPS showed cytotoxicity against thymocytes in the presence of rabbit complements. Binding and cytotoxicity were confirmed by IgM purified from serum of the mice injected with C. ochracea LPS. Furthermore, serum of mice treated with C. ochracea, F. nucleatum or A. actinomycetemcomitans LPS inhibited the proliferation of thymocytes. However, purified IgM from the serum of mice treated with C. ochracea LPS failed to produce the same inhibition. Our results suggest that LPS from certain species of periodontopathic bacteria can induce IgM-ATA in the serum and these antibodies may modulate the local immune network in periodontal tissues.