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Infection and Immunity, March 2001, p. 1499-1507, Vol. 69, No. 3
Department of Microbiology, Bose Institute,
Calcutta 700 054, India,1 and Department
of Surgery, College of Medicine, University of Tennessee, Memphis,
Tennessee 381632
Received 24 July 2000/Returned for modification 25 September
2000/Accepted 1 December 2000
Leishmania donovani, an intracellular protozoan
parasite, challenges host defense mechanisms by impairing the signal
transduction of macrophages. In this study we investigated whether
interleukin-10 (IL-10)-mediated alteration of signaling events in a
murine model of visceral leishmaniasis is associated with macrophage
deactivation. Primary in vitro cultures of macrophages infected with
leishmanial parasites markedly elevated the endogenous release of
IL-10. Treatment with either L. donovani or recombinant
IL-10 (rIL-10) inhibited both the activity and expression of the
Ca2+-dependent protein kinase C (PKC) isoform. However,
preincubation with neutralizing anti-IL-10 monoclonal antibody (MAb)
restored the PKC activity in the parasitized macrophage. Furthermore,
we observed that coincubation of macrophages with rIL-10 and L. donovani increased the intracellular parasite burden, which was
abrogated by anti-IL-10 MAb. Consistent with these observations,
generation of superoxide (O2
0019-9567/01/$04.00+0 DOI: 10.1128/IAI.69.3.1499-1507.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
Immunomodulatory Role of Interleukin-10 in Visceral
Leishmaniasis: Defective Activation of Protein Kinase
C-Mediated Signal Transduction Events
) and nitric
oxide and the release of murine tumor necrosis factor-
were
attenuated in response to L. donovani or rIL-10 treatment. On the other hand, preincubation of the infected macrophages with neutralizing anti-IL-10 MAb significantly blocked the inhibition of
nitric oxide and murine tumor necrosis factor-
release by the
infected macrophages. These findings imply that infection with L. donovani induces endogenous secretion of murine IL-10, which in
turn facilitates the intracellular survival of the protozoan and
orchestrates several immunomodulatory roles via selective impairment of
PKC-mediated signal transduction.
*
Corresponding author. Mailing address: Department of
Microbiology, Bose Institute, P 1/12, C.I.T. Scheme VII M, Calcutta 700 054, India. Phone: 91-33-337-9416. Fax: 91-33-334-3886. E-mail: subrata{at}boseinst.ernet.in.
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