Infection and Immunity, May 1999, p. 2125-2130, Vol. 67, No. 5
0019-9567/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
Department of Endodontics, Boston University School of Dental Medicine, Boston, Massachusetts 02118
Received 3 December 1998/Accepted 9 February 1999
Viridans streptococci are a heterogeneous group of gram-positive
bacteria that are normal inhabitants of the mouth. These organisms are
thought to contribute significantly to the etiology of infective
endocarditis, although recently they have been implicated in serious
infections in other settings. Another group of oral bacteria,
gram-negative anaerobes, is associated with chronic dental infections,
such as periodontal diseases or endodontic lesion formation. We
evaluated the ability of the oral pathogens Streptococcus
mutans and Porphyromonas endodontalis to induce a
pathogenic response in vivo, with the goal of quantifying the inflammatory response in soft tissue by measuring leukocyte recruitment and hard tissues by measuring osteoclastogenesis. S. mutans
induced a strong inflammatory response and was a potent inducer of
osteoclast formation, while P. endodontalis was not. To
further study the mechanisms by which P. endodontalis and
S. mutans elicit significantly different levels of
inflammatory responses in vivo, we tested the capacity of each to
induce production of cytokines by mononuclear cells in vitro. S. mutans stimulated high levels of interleukin-12 (IL-12), gamma
interferon (IFN-
), and tumor necrosis factor alpha (TNF-
), all of
which are associated with inflammation, enhanced monocyte function, and
generation of a Th1 response. In contrast, P. endodontalis
stimulated production of IL-10 but not of TNF-
, IL-12, or IFN-
.
These results demonstrate that oral pathogens differ dramatically in
their abilities to induce inflammatory and immunoregulatory cytokines.
Moreover, there is a high degree of correlation between the cytokine
profile induced by these bacteria in vitro and their pathogenic
capacity in vivo.
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