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Infection and Immunity, April 2000, p. 1893-1898, Vol. 68, No. 4
Department of Oral Biology and Oral Medicine,
Dental Research Institute,1 and
Department of Microbiology and Molecular Genetics, UCLA
School of Medicine and Dentistry,2
University of California, Los Angeles, California 90095
Received 6 July 1999/Returned for modification 8 November
1999/Accepted 3 January 2000
It is largely unknown why a variety of bacteria present in the oral
cavity are capable of establishing themselves in the
periodontal pockets of nonimmunocompromised individuals in the presence
of competent immune effector cells. In this paper we present evidence for the immunosuppressive role of Fusobacterium nucleatum,
a gram-negative oral bacterium which plays an important role in the
generation of periodontal disease. Our studies indicate that the
immunosuppressive role of F. nucleatum is largely due to
the ability of this organism to induce apoptotic cell death in
peripheral blood mononuclear cells (PBMCs) and in
polymorphonuclear cells (PMNs). F. nucleatum treatment
induced apoptosis of PBMCs and PMNs as assessed by an increase in subdiploid DNA content determined by DNA
fragmentation and terminal deoxynucleotidyltransferase-mediated
dUTP-biotin nick end-labeling assays. The ability of F. nucleatum to induce apoptosis was abolished by either heat
treatment or proteinase digestion but was retained after formaldehyde
treatment, suggesting that a heat-labile surface protein
component is responsible for bacterium-mediated cell apoptosis.
The data also indicated that F. nucleatum-induced cell
apoptosis requires activation of caspases and is protected by
NF-
0019-9567/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Induction of Apoptotic Cell Death in Peripheral Blood Mononuclear
and Polymorphonuclear Cells by an Oral Bacterium,
Fusobacterium nucleatum

B. Possible mechanisms of F. nucleatum's role in the
pathogenesis of periodontal disease are discussed.
*
Corresponding author. Mailing address: Department of
Oral Biology and Oral Medicine, Dental Research Institute, University of California, Los Angeles, CA 90095. Phone: (310) 206-3970. Fax: (310)
794-7109. E-mail: ajewett{at}ucla.edu.
Present address: Department of Oral Biology, State University of
New York, Buffalo, NY 14214.
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