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Infect. Immun., Jan 1998, 65-69, Vol 66, No. 1
JK Brieland, DG Remick, ML LeGendre, NC Engleberg and JC Fantone
The in vivo role of endogenous interleukin 12 (IL-12) in modulating
intrapulmonary growth of Legionella pneumophila was assessed by using a
murine model of replicative L. pneumophila lung infection. Intratracheal
inoculation of A/J mice with virulent bacteria (10(6) L. pneumophila cells
per mouse) resulted in induction of IL-12, which preceded clearance of the
bacteria from the lung. Inhibition of endogenous IL-12 activity, via
administration of IL-12 neutralizing antiserum, resulted in enhanced
intrapulmonary growth of the bacteria within 5 days postinfection (compared
to untreated L. pneumophila- infected mice). Because IL-12 has previously
been shown to modulate the expression of cytokines, including gamma
interferon (IFN-gamma), tumor necrosis factor alpha (TNF-alpha), and IL-10,
which regulate L. pneumophila growth, immunomodulatory effects of
endogenous IL-12 on intrapulmonary levels of these cytokines during
replicative L. pneumophila lung infection were subsequently assessed.
Results of these experiments demonstrated that TNF-alpha activity was
significantly lower, while protein levels of IFN-gamma and IL-10 in the
lung were similar, in L. pneumophila-infected mice administered IL-12
antiserum, compared to similarly infected untreated mice. Together, these
results demonstrate that IL-12 is critical for resolution of replicative L.
pneumophila lung infection and suggest that regulation of intrapulmonary
growth of L. pneumophila by endogenous IL-12 is mediated, at least in part,
by TNF-alpha.
Copyright © 1998, American Society for Microbiology
In vivo regulation of replicative Legionella pneumophila lung infection by endogenous interleukin-12
Unit for Laboratory Animal Medicine, The University of Michigan Medical School, Ann Arbor 48109-0614, USA. jbrie@umich.edu
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