Circulating blood monocytes supply peripheral tissues with macrophage and dendritic cell (DC) precursors and, in the setting of infection, also contribute directly to immune defense against microbial pathogens. In humans and mice, monocytes are divided into two major subsets that either specifically traffic into inflamed tissues or, in the absence of overt inflammation, constitutively maintain tissue macrophage/DC populations. Inflammatory monocytes respond rapidly to microbial stimuli by secreting cytokines and antimicrobial factors, express the CCR2 chemokine receptor, and traffic to sites of microbial infection in response to monocyte chemoattractant protein (MCP)-1 (CCL2) secretion. In murine models, CCR2-mediated monocyte recruitment is essential for defense against Listeria monocytogenes, Mycobacterium tuberculosis, Toxoplasma gondii, and Cryptococcus neoformans infection, implicating inflammatory monocytes in defense against bacterial, protozoal, and fungal pathogens. Recent studies indicate that inflammatory monocyte recruitment to sites of infection is complex, involving CCR2-mediated emigration of monocytes from the bone marrow into the bloodstream, followed by trafficking into infected tissues. The in vivo mechanisms that promote chemokine secretion, monocyte differentiation and trafficking, and finally monocyte-mediated microbial killing remain active and important areas of investigation.

中文翻译：

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单核细胞介导的对微生物病原体的防御。

循环血液单核细胞为外周组织提供巨噬细胞和树突状细胞 (DC) 前体，并且在感染的情况下，还直接有助于针对微生物病原体的免疫防御。在人类和小鼠中，单核细胞分为两个主要亚群，它们要么专门进入发炎组织，要么在没有明显炎症的情况下组成性地维持组织巨噬细胞/DC 种群。炎性单核细胞通过分泌细胞因子和抗菌因子对微生物刺激做出快速反应，表达 CCR2 趋化因子受体，并响应单核细胞趋化蛋白 (MCP)-1 (CCL2) 的分泌进入微生物感染部位。在小鼠模型中，CCR2 介导的单核细胞募集对于防御单核细胞增生李斯特菌、结核分枝杆菌、弓形虫、新型隐球菌感染，这表明炎症单核细胞防御细菌、原生动物和真菌病原体。最近的研究表明炎症单核细胞募集到感染部位是复杂的，涉及 CCR2 介导的单核细胞从骨髓迁移到血液中，然后转移到受感染的组织中。促进趋化因子分泌、单核细胞分化和运输以及最终单核细胞介导的微生物杀伤的体内机制仍然是活跃和重要的研究领域。涉及 CCR2 介导的单核细胞从骨髓迁移到血液中，然后进入受感染组织。促进趋化因子分泌、单核细胞分化和运输以及最终单核细胞介导的微生物杀伤的体内机制仍然是活跃和重要的研究领域。涉及 CCR2 介导的单核细胞从骨髓迁移到血液中，然后进入受感染的组织。促进趋化因子分泌、单核细胞分化和运输以及最终单核细胞介导的微生物杀伤的体内机制仍然是活跃和重要的研究领域。