The CXC Chemokines Gamma Interferon (IFN-γ)-Inducible Protein 10 and Monokine Induced by IFN-γ Are Released during Severe Melioidosis

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Abstract
Gamma interferon (IFN-γ)-inducible protein 10 (IP-10) and monokine induced by IFN-γ (Mig) are related CXC chemokines which bind to the CXCR3 receptor and specifically target activated T lymphocytes and natural killer (NK) cells. The production of IP-10 and Mig by various cell types in vitro is strongly dependent on IFN-γ. To determine whether IP-10 and Mig are released during bacterial infection in humans, we measured plasma levels of IP-10 and Mig in patients with melioidosis, a severe gram-negative infection caused byBurkholderia pseudomallei. IP-10 and Mig were markedly elevated in patients with melioidosis on admission, particularly in blood culture-positive patients, and remained elevated during the 72-h study period. Levels of IP-10 and Mig showed a positive correlation with IFN-γ concentrations and also correlated with clinical outcome. In whole blood stimulated with heat-killedB. pseudomallei, neutralization of IFN-γ and tumor necrosis factor alpha (TNF-α) partly attenuated IP-10 and Mig release, while anti-interleukin-12 (IL-12) and anti-IL-18 had a synergistic effect. Stimulation with other bacteria or endotoxin also induced strong secretion of IP-10 and Mig. These data suggest that IP-10 and Mig are part of the innate immune response to bacterial infection. IP-10 and Mig may contribute to host defense in Th1-mediated host defense during infections by attracting CXCR3+Th1 cells to the site of inflammation.