OKAYAMA, Japan, November 26, 2018 /PRNewswire/ --
Researchers at Okayama University report in the
Journal of Periodontology that the presence of
commensal flora in the mouth may play a key role in the functioning
of the immune system against periodontal infections.
(Photo:
https://mma.prnewswire.com/media/789311/Okayama_Fig1.jpg )
The development of an animal's immune system relies on commensal
flora - microorganisms such as bacteria present in certain parts of
the body. In the case of immunity against periodontal diseases -
infections of the areas surrounding teeth - it is unclear, however,
what exactly the role of commensal flora is. Now, Professor
Manabu Morita from Okayama
University and colleagues have investigated the relation between
commensal flora in the mouth and the immune response to a bacterium
called Porphyromonas gingivalis (P. gingivalis),
which contains lipopolysaccharide (LPS), a known periodontal
pathogen.
The researchers tested the immune response of mice after the
application of P. gingivalis /LPS. Two types of mouse
were used in the experiments: germ-free and specific-pathogen-free
mice. The former are free of any microorganisms, including
commensal flora; the latter are mice guaranteed to be free of
certain pathogens - in this case, periodontal pathogens - but not
of commensal flora.
The response to the bacterium was assessed by the amounts of
particular types of cells that are characteristic of immune system
activation. Four groups of mice were monitored: a 'baseline' group
not exposed to P. gingivalis and three groups to which the
bacterium was applied; each of the three groups was then examined
at different points in time after the application of LPS.
The scientists observed that exposure to P. gingivalis
led to an increase in the number of a certain type of cell
associated with immune system activity in the
specific-pathogen-free mice, after 3 hours, indicating that
application of the bacterium indeed triggered the immune system. At
the same time, the germ-free mice did not show similar increased
levels of these cells, suggesting that commensal flora contribute
to the development and functioning of the periodontal immune
system.
Professor Morita and colleagues are aware of the limitations of
their study. They did not, for example, investigate the effect of
repeatedly applying LPS. They also acknowledge that only a limited
set of cell types characteristic of immune system activity was
monitored. Therefore, the scientists concluded that "[the] results,
though suggestive, should be interpreted with caution."
Background:
R Commensal flora
Flora is the term for a community of bacteria and other
microorganisms in a part of an animal's body. The term commensal
flora is used when the presence of the flora is not harmful for the
animal host. Professor Manabu Morita
from Okayama University and colleagues have now studied the role of
commensal flora in the gingival sulcus - the area between a tooth
and surrounding tissues - on the development of proper periodontal
immune responses.
Lipopolysaccharide
A lipopolysaccharide (LPS) is a large organic molecule
consisting of a lipid and a polysaccharide; LPS molecules occur in
certain types of bacteria. LPS is known to be toxic, and typically
triggers immune response activation. Professor Morita and
colleagues have now investigated whether immune response to LPS,
when applied via the bacterium Porphyromonas gingivalis
(P. gingivalis), is influenced by the presence of commensal
flora in the gingival sulcus.
Reference
Daiki Fukuhara, Koichiro Irie, Yoko
Uchida, Kota Kataoka, Kentaro
Akiyama, Daisuke Ekuni, Takaaki Tomofuji, Manabu Morita. Impact of commensal flora on
periodontal immune response to lipopolysaccharide. Journal of
Periodontology, 2018;89:1213-1220.
DOI: 10.1002/JPER.17-0567
https://onlinelibrary.wiley.com/doi/abs/10.1002/JPER.17-0567
Okayama University
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About Okayama University
Okayama University is one of the largest comprehensive
universities in Japan with roots
going back to the Medical Training Place sponsored by the Lord of
Okayama and established in 1870. Now with 1,300 faculty and 13,000
students, the University offers courses in specialties ranging from
medicine and pharmacy to humanities and physical sciences. Okayama
University is located in the heart of Japan approximately 3 hours west of
Tokyo by Shinkansen.
Website: http://www.okayama-u.ac.jp/index_e.html
Correspondence to
Professor Manabu Morita, D.D.S.,
Ph.D.
Department of Preventive Dentistry,
Okayama University Graduate School of Medicine, Dentistry and
Pharmaceutical Sciences, 2-5-1 Shikata-cho, Kita-ku, Okayama,
700-8558, Japan.
E-mail: mmorita@md.okayama-u.ac.jp
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