Effect ofMycobacterium tuberculosis-Specific 10-Kilodalton Antigen on Macrophage Release of Tumor Necrosis Factor Alpha and Nitric Oxide

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Abstract
Secreted proteins ofMycobacterium tuberculosisare major targets of the specific immunity in tuberculosis and constitute promising candidates for the development of more efficient vaccines and diagnostic tests. We show here thatM. tuberculosis-specific antigen 10 (MTSA-10, originally designated CFP-10) can bind to the surface of mouse J774 macrophage-like cells and stimulate the secretion of the proinflammatory cytokine tumor necrosis factor alpha (TNF-α). MTSA-10 also synergized with gamma interferon (IFN-γ) for the induction of the microbicidal free radical nitric oxide (NO) in J774 cells, as well as in bone marrow-derived and peritoneal macrophages. On the other hand, pretreatment of J774 cells with MTSA-10 markedly reduced NO but not TNF-α or interleukin 10 (IL-10) release upon subsequent stimulation with lipopolysaccharide or the cell lysate ofM. tuberculosis. The presence of IFN-γ during stimulation withM. tuberculosislysate antagonized the desensitizing effect of MTSA-10 pretreatment on macrophage NO production. The activation of protein tyrosine kinases (PTK) and the serine/threonine kinases p38 MAPK and ERK was apparently required for MTSA-10 induction of TNF-α and NO release, as revealed by specific kinase inhibitors. However, only p38 MAPK activity, not PTK or ERK activity, was partly responsible for MTSA-10-mediated macrophage desensitization. The modulation of macrophage function by MTSA-10 suggests a novel mechanism for its involvement in immunopathogenesis of tuberculosis and might have implications for the prevention, diagnosis, and therapy of this disease.