Key Points Mtb LAM stimulates neutrophil cytokine production via TLR2/1 signaling. Mtb LAM–elicited neutrophil responses are distinct from the TLR2/1 agonist Pam3CSK4. Neutrophils, polymorphonuclear (PMN) leukocytes, play an important role in the early innate immune response to Mycobacterium tuberculosis infection in the lung. Interactions between PMN and mycobacterial lipids impact the activation state of these migrated cells with consequences for the surrounding tissue in terms of resolution versus ongoing inflammation. We hypothesized that lipoarabinomannan from M. tuberculosis (Mtb LAM) would prime human PMN in a TLR2-dependent manner and investigated this with specific comparison with the purified synthetic TLR2 agonists, Pam3CSK4 and FSL-1. In contrast to Pam3CSK4 and FSL-1, we found Mtb LAM did not induce any of the classical PMN priming phenotypes, including enhancement of NADPH oxidase activity, shedding of l-selectin, or mobilization of CD11b. However, exposure of PMN to Mtb LAM did elicit pro- and anti-inflammatory cytokine production and release in a TLR2/1-dependent manner, using the TLR1 single-nucleotide polymorphism rs5743618 (1805G/T) as a marker for TLR2/1 specificity. Moreover, Mtb LAM did not elicit p38 MAPK phosphorylation or endocytosis, although these processes occurred with Pam3CSK4 stimulation, and were necessary for the early priming events to occur. Interestingly, Mtb LAM did not abrogate priming responses elicited by Pam3CSK4. Notably, subfractionation of light membranes from Pam3CSK4 versus Mtb LAM–stimulated cells demonstrated differential patterns of exocytosis. In summary, Mtb LAM activates PMN via TLR2/1, resulting in the production of cytokines but does not elicit early PMN priming responses, as seen with Pam3CSK4. We speculate that the inability of Mtb LAM to prime PMN may be due to differential localization of TLR2/1 signaling.

中文翻译：

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结核分枝杆菌脂阿拉伯甘露聚糖通过不同于 Pam3CSK4 的 TLR2/1 机制激活人类中性粒细胞

关键点 Mtb LAM 通过 TLR2/1 信号传导刺激中性粒细胞细胞因子的产生。Mtb LAM 引起的中性粒细胞反应与 TLR2/1 激动剂 Pam3CSK4 不同。中性粒细胞，即多形核 (PMN) 白细胞，在肺结核分枝杆菌感染的早期先天免疫反应中起重要作用。PMN 和分枝杆菌脂质之间的相互作用会影响这些迁移细胞的激活状态，从而对周围组织的消退与持续炎症产生影响。我们假设来自结核分枝杆菌 (Mtb LAM) 的脂阿拉伯甘露聚糖会以 TLR2 依赖性方式引发人类 PMN，并通过与纯化的合成 TLR2 激动剂 Pam3CSK4 和 FSL-1 进行特定比较来研究这一点。与 Pam3CSK4 和 FSL-1 相比，我们发现 Mtb LAM 不诱导任何经典的 PMN 启动表型，包括 NADPH 氧化酶活性的增强、l-选择素的脱落或 CD11b 的动员。然而，使用 TLR1 单核苷酸多态性 rs5743618 (1805G/T) 作为 TLR2/1 特异性标记物，PMN 暴露于 Mtb LAM 确实以 TLR2/1 依赖性方式引起促炎和抗炎细胞因子的产生和释放. 此外，Mtb LAM 不会引发 p38 MAPK 磷酸化或内吞作用，尽管这些过程发生在 Pam3CSK4 刺激下，并且是发生早期启动事件所必需的。有趣的是，Mtb LAM 并没有消除 Pam3CSK4 引发的启动反应。值得注意的是，来自 Pam3CSK4 与 Mtb LAM 刺激细胞的轻膜的亚分级显示出不同的胞吐模式。总之，Mtb LAM 通过 TLR2/1 激活 PMN，导致细胞因子的产生，但不会引发早期 PMN 启动反应，如 Pam3CSK4 所见。我们推测 Mtb LAM 无法启动 PMN 可能是由于 TLR2/1 信号的不同定位。