Neutrophils are innate immune cells implicated in the process of killing Mycobacterium tuberculosis early during infection. Once the mycobacteria enter the human system, neutrophils sense and engulf them. By secreting bactericidal enzymes and α-defensins like human neutrophil peptides loaded in their granule armory, neutrophils kill the pathogen. Peripheral blood neutrophils secrete a wide range of cytokines like IL-8, IL-1-β and IFN-γ in response to mycobacterial infection. Thus they signal and activate distant immune cells thereby informing them of prevailing infection. The activated monocytes, dendritic cells and T cells further continue the immune response. As a final call, neutrophils release neutrophil extracellular traps in circulation which can trap mycobacteria in patients with active pulmonary tuberculosis. Extensive neutrophilic response is associated with inflammation, pulmonary destruction, and pathology. For example, inappropriate phagocytosis of mycobacteria-infected neutrophils can damage host cells due to necrosis of neutrophils, leading to chronic inflammation and tissue damage. This dual nature of neutrophils makes them double-edged swords during tuberculosis, and hence data available on neutrophil functions against mycobacterium are controversial and non-uniform. This article reviews the role of neutrophils in tuberculosis infection and highlights research gaps that need to be addressed. We focus on our understanding of new research ideologies targeting neutrophils (a) in the early stages of infection for boosting specific immune functions or (b) in the later stages of infection to prevent inflammatory conditions mediated by activated neutrophils. This would plausibly lead to the development of better tuberculosis vaccines and therapeutics in the future.

中文翻译：

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中性粒细胞在结核病中的作用：鸟瞰图。


中性粒细胞是先天免疫细胞，参与感染早期杀死结核分枝杆菌的过程。一旦分枝杆菌进入人体系统，中性粒细胞就会感知并吞噬它们。通过分泌杀菌酶和α-防御素（如颗粒军械库中装载的人类中性粒细胞肽），中性粒细胞杀死病原体。外周血中性粒细胞响应分枝杆菌感染而分泌多种细胞因子，如 IL-8、IL-1-β 和 IFN-γ。因此，它们向远处的免疫细胞发出信号并激活，从而告知它们当前的感染情况。激活的单核细胞、树突状细胞和T细胞进一步继续免疫反应。最后，中性粒细胞在循环中释放中性粒细胞胞外捕获物，这些捕获物可以捕获活动性肺结核患者的分枝杆菌。广泛的中性粒细胞反应与炎症、肺部破坏和病理有关。例如，分枝杆菌感染的中性粒细胞的不适当吞噬作用会因中性粒细胞坏死而损害宿主细胞，导致慢性炎症和组织损伤。中性粒细胞的这种双重性质使其在结核病期间成为双刃剑，因此有关中性粒细胞对抗分枝杆菌功能的可用数据存在争议且不一致。本文回顾了中性粒细胞在结核感染中的作用，并强调了需要解决的研究空白。我们专注于理解针对中性粒细胞的新研究理念（a）在感染早期阶段增强特定免疫功能，或（b）在感染后期阶段预防由活化的中性粒细胞介导的炎症状况。 这可能会导致未来更好的结核病疫苗和治疗方法的开发。