Innate immune cells, including macrophages and dendritic cells, protect the host from pathogenic assaults in part through secretion of a program of cytokines and chemokines (C/Cs). Cell-to-cell variability in C/C secretion appears to contribute to the regulation of the immune response, but the sources of secretion variability are largely unknown. To begin to track the biological sources that control secretion variability, we developed and validated a microfluidic device to integrate live-cell imaging of fluorescent reporter proteins with a single-cell assay of protein secretion. We used this device to image NF-κB RelA nuclear translocation dynamics and Tnf transcription dynamics in macrophages in response to stimulation with the bacterial component lipopolysaccharide (LPS), followed by quantification of secretion of TNF, CCL2, CCL3, and CCL5. We found that the timing of the initial peak of RelA signaling in part determined the relative level of TNF and CCL3 secretion, but not CCL2 and CCL5 secretion. Our results support evidence that differences in timing across cell processes partly account for cell-to-cell variability in downstream responses, but that other factors introduce variability at each biological step.

中文翻译：

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微流体平台使信号和转录的活细胞成像与同一单细胞中的多重分泌测量相结合。

先天免疫细胞，包括巨噬细胞和树突状细胞，部分通过分泌细胞因子和趋化因子 (C/Cs) 程序来保护宿主免受病原体攻击。C/C 分泌的细胞间变异似乎有助于调节免疫反应，但分泌变异的来源在很大程度上是未知的。为了开始追踪控制分泌变异性的生物来源，我们开发并验证了一种微流体装置，可将荧光报告蛋白的活细胞成像与蛋白质分泌的单细胞测定相结合。我们使用该设备对巨噬细胞中的 NF-κB RelA 核易位动力学和 Tnf 转录动力学进行成像，以响应细菌成分脂多糖 (LPS) 的刺激，然后量化 TNF、CCL2、CCL3 和 CCL5 的分泌。我们发现 RelA 信号初始峰值的时间部分决定了 TNF 和 CCL3 分泌的相对水平，但不决定 CCL2 和 CCL5 分泌的相对水平。我们的结果支持的证据表明，跨细胞过程的时间差异部分解释了下游反应中细胞间的变异性，但其他因素在每个生物步骤中引入了变异性。