In response to GM-CSF or M-CSF, macrophages (MΦ) can acquire pro- or anti-inflammatory properties, respectively. Given the importance of CD14 and Toll-like receptor (TLR) 4 in lipopolysaccharide (LPS)-induced signaling, we studied the effect of anti-CD14 antibody mediated CD14 blockade on LPS-induced cytokine production, signal transduction and on the expression levels of CD14 and TLR4 in GM-MΦ and M-MΦ. We found M-MΦ to express higher levels of both surface antigens and to produce more interferon (IFN)-β and interleukin-10, but less tumor necrosis factor (TNF)-α than GM-MΦ. Blockage of CD14 at high LPS concentrations increased the production of proinflammatory cytokines and decreased that of IFN-β in M-MΦ but not in GM-MΦ. We show that phosphorylation states of signaling molecules of the MyD88 (myeloid differentiation primary response 88), TRIF (TIR-domain-containing adapter-inducing IFN-β) and MAPK (mitogen-activated protein kinase) pathways are not altered in any way that would account for the cytokine overshoot reaction. However, CD14 blockage in M-MΦ decreased TLR4 and CD14 expression levels, regardless of the presence of LPS, indicating that the loss of the surface molecules prevented LPS from initiating TRIF signaling. As TNF-α synthesis was even upregulated under these experimental conditions, we suggest that TRIF is normally involved in restricting LPS-induced TNF-α overproduction. Thus, surface CD14 plays a decisive role in the biological response by determining LPS-induced signaling.

中文翻译：

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CD14调节巨噬细胞亚群中脂多糖诱导的肿瘤坏死因子-α的产生。

响应于GM-CSF或M-CSF，巨噬细胞（MΦ）可以分别获得促炎或抗炎特性。鉴于CD14和Toll样受体（TLR）4在脂多糖（LPS）诱导的信号传导中的重要性，我们研究了抗CD14抗体介导的CD14阻断对LPS诱导的细胞因子产生，信号转导以及其表达水平的影响。 GM-MΦ和M-MΦ中的CD14和TLR4。我们发现M-MΦ可以表达更高水平的两种表面抗原，并比GM-MΦ产生更多的干扰素（IFN）-β和白介素10，但肿瘤坏死因子（TNF）-α更少。在高LPS浓度下，CD14的阻断增加了M-MΦ中促炎细胞因子的产生，并降低了IFN-β的产生，而在GM-MΦ中则没有。我们显示了MyD88信号分子的分子的磷酸化状态（骨髓分化主要反应88），TRIF（含TIR结构域的衔接子诱导IFN-β）和MAPK（丝裂原激活的蛋白激酶）途径未发生任何改变，这可解释细胞因子过冲反应。但是，无论LPS的存在如何，M-MΦ中的CD14阻断都会降低TLR4和CD14表达水平，这表明表面分子的丢失阻止LPS引发TRIF信号传导。由于在这些实验条件下TNF-α的合成甚至被上调，我们建议TRIF通常参与限制LPS诱导的TNF-α的过度生产。因此，表面CD14通过确定LPS诱导的信号传导在生物反应中起决定性作用。不管LPS的存在如何，M-MΦ中的CD14阻断都会降低TLR4和CD14表达水平，这表明表面分子的丢失阻止了LPS引发TRIF信号传导。由于在这些实验条件下TNF-α的合成甚至被上调，我们建议TRIF通常参与限制LPS诱导的TNF-α的过度生产。因此，表面CD14通过确定LPS诱导的信号传导在生物反应中起决定性作用。不管LPS的存在如何，M-MΦ中的CD14阻断都会降低TLR4和CD14表达水平，这表明表面分子的丢失阻止了LPS引发TRIF信号传导。由于在这些实验条件下TNF-α的合成甚至被上调，我们建议TRIF通常参与限制LPS诱导的TNF-α的过度生产。因此，表面CD14通过确定LPS诱导的信号传导在生物反应中起决定性作用。