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Infection and Immunity, December 2003, p. 7023-7034, Vol. 71, No. 12
0019-9567/03/$08.00+0 DOI: 10.1128/IAI.71.12.7023-7034.2003
Copyright © 2003, American Society for Microbiology. All Rights Reserved.
Department of Infectious Diseases and Microbiology, Graduate School of Public Health,1 Department of Molecular Genetics and Biochemistry, School of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania2
Received 25 April 2003/ Returned for modification 17 June 2003/ Accepted 20 August 2003
Tuberculosis
remains a major public health problem worldwide. Chemokines and
cytokines organize and direct infiltrating cells to sites of infection,
and these molecules likely play crucial roles in granuloma formation
and maintenance. To address this issue, we used in situ hybridization
(ISH) to measure chemokine and cytokine mRNA expression levels and
patterns directly in lung tissues from cynomolgus macaques (Macaca
fascicularis) experimentally infected with a low dose of virulent
Mycobacterium tuberculosis. We examined more than 300
granulomas and observed abundant expression of gamma interferon
(IFN-
)-inducible chemokine mRNAs (CXCL9/monokine induced by
IFN-
, CXCL10/IFN-
-inducible protein, and
CXCL11/IFN-
-inducible T-cell
-chemoattractant) within
solid and caseous granulomas, and there was only minimal expression in
nongranulomatous regions of tissue. The mRNA expression patterns of
IFN-
and tumor necrosis factor alpha were examined in
parallel, and the results revealed that cytokine
mRNA+ cells were abundant and generally localized to
the granulomas. Mycobacterial 16S rRNA expression was also measured by
ISH, and the results revealed that there was localization predominantly
to the granulomas and that the highest signal intensity was in caseous
granulomas. We observed several granulomatous lesions with
exceptionally high levels of RNA for mycobacterial 16S rRNA,
IFN-
, and IFN-
-inducible chemokines, suggesting that
the local presence of mycobacteria is partially responsible for the
upregulation of IFN-
-inducible chemokines and recruitment of
CXCR3+ cells, which were also abundant in
granulomatous lesions. These results suggest that expression of CXCR3
ligands and the subsequent recruitment of CXCR3+
cells are involved in granuloma formation and
maintenance.
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