Immunobiology Section, Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892, USA.
J Immunol. 2011 Sep 1;187(5):2540-7. doi: 10.4049/jimmunol.1100926. Epub 2011 Jul 22.
Mycobacterium tuberculosis is a virulent intracellular pathogen that survives in macrophages even in the presence of an intact adaptive immune response. Type I IFNs have been shown to exacerbate tuberculosis in mice and to be associated with disease progression in infected humans. Nevertheless, the mechanisms by which type I IFNs regulate the host response to M. tuberculosis infection are poorly understood. In this study, we show that M. tuberculosis induces an IFN-related gene expression signature in infected primary human macrophages, which is dependent on host type I IFN signaling as well as the mycobacterial virulence factor, region of difference-1. We further demonstrate that type I IFNs selectively limit the production of IL-1β, a critical mediator of immunity to M. tuberculosis. This regulation occurs at the level of IL1B mRNA expression, rather than caspase-1 activation or autocrine IL-1 amplification and appears to be preferentially used by virulent mycobacteria since avirulent M. bovis bacillus Calmette-Guérin (BCG) fails to trigger significant expression of type I IFNs or release of mature IL-1β protein. The latter property is associated with decreased caspase-1-dependent IL-1β maturation in the BCG-infected macrophages. Interestingly, human monocytes in contrast to macrophages produce comparable levels of IL-1β in response to either M. tuberculosis or BCG. Taken together, these findings demonstrate that virulent and avirulent mycobacteria employ distinct pathways for regulating IL-1β production in human macrophages and reveal that in the case of M. tuberculosis infection the induction of type I IFNs is a major mechanism used for this purpose.
结核分枝杆菌是一种毒力很强的细胞内病原体,即使在完整的适应性免疫反应存在的情况下,它也能在巨噬细胞中存活。已经证明,I 型干扰素会使小鼠的结核病恶化,并与感染人类的疾病进展有关。然而,I 型干扰素调节宿主对结核分枝杆菌感染的反应的机制还知之甚少。在这项研究中,我们表明,结核分枝杆菌在受感染的原代人巨噬细胞中诱导了一个与干扰素相关的基因表达特征,这依赖于宿主 I 型干扰素信号以及分枝杆菌毒力因子 RD1。我们进一步证明,I 型干扰素选择性地限制了 IL-1β的产生,IL-1β是对结核分枝杆菌免疫的关键介质。这种调节发生在 IL1B mRNA 表达水平,而不是半胱天冬酶-1 激活或自分泌 IL-1 扩增,而且似乎优先被毒力分枝杆菌使用,因为无毒力的牛分枝杆菌卡介苗(BCG)不能触发 I 型干扰素或成熟的 IL-1β蛋白的大量释放。后一特性与 BCG 感染的巨噬细胞中依赖半胱天冬酶-1 的 IL-1β成熟减少有关。有趣的是,与巨噬细胞相比,人单核细胞对结核分枝杆菌或 BCG 的反应都能产生相当水平的 IL-1β。总之,这些发现表明,毒力和无毒力分枝杆菌在人类巨噬细胞中使用不同的途径来调节 IL-1β的产生,并揭示了在结核分枝杆菌感染的情况下,I 型干扰素的诱导是用于此目的的主要机制。