Intracellular expression of Mycobacterium tuberculosis-specific 10-kDa antigen down-regulates macrophage B7.1 expression and nitric oxide release.
To explore the role of the 10-kDa Mycobacterium tuberculosis-specific secreted antigen (MTSA-10 or CFP-10) in modulation of macrophage function, J774 macrophages were transfected stably with DNA encoding MTSA-10. Compared to normal or mock-transfected controls, MTSA-10-expressing macrophages had markedly lower levels of co-stimulatory molecule B7.1 on their surface, while the expression of B7.2 and ICAM-1 was not affected. MTSA-transfected cells also produced significantly less microbicidal free radical nitric oxide (NO) upon stimulation with interferon (IFN)-gamma, lipopolysaccharide or M. tuberculosis cell lysate. Western blot analysis revealed the absence of tyrosine-phosphorylated protein slightly larger than 112 kDa in MTSA-transfected macrophages. Moreover, the treatment of control J774 cells with protein tyrosine kinase inhibitor genistein completely mimicked the effects of transfection with MTSA-10, selectively down-regulating NO and B7.1, but not B7.2 or ICAM-1 expression. The observed MTSA-10-mediated block of B7.1 expression and NO release might contribute to the suppression of antimycobacterial response in tuberculosis.
Singh
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B
Immunology Group, International Centre for Genetic Engineering and Biotechnology, New Delhi, India.
Singh
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G
Trajkovic
V
V
Sharma
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P
D000818:Animals; D000942:Antigens, Bacterial / Q000378:metabolism*; D018122:B7-1 Antigen / Q000378:metabolism*; D015153:Blotting, Western; D002460:Cell Line; D005434:Flow Cytometry; D008264:Macrophages / Q000276:immunology* / Q000378:metabolism; D051379:Mice; D009169:Mycobacterium tuberculosis / Q000276:immunology*; D009569:Nitric Oxide / Q000378:metabolism*; D010766:Phosphorylation; D014162:Transfection / Q000379:methods; D014443:Tyrosine / Q000378:metabolism
D000942:Antigens, Bacterial; D018122:B7-1 Antigen; D009569:Nitric Oxide; D014443:Tyrosine