Uronen-Hansson Heli, Allen Jennifer, Osman Mohamed, Squires Ginette, Klein Nigel, Callard Robin E
Immunobiology Unit, Institute of Child Health, UCL, London, UK.
Immunology. 2004 Feb;111(2):173-8. doi: 10.1111/j.0019-2805.2003.01803.x.
The activation of dendritic cells (DCs) by microbes is mediated by pattern recognition receptors including the Toll-like receptors (TLR). Bacterial lipopolysaccharide acts via TLR4 whereas peptidoglycan and lipoprotein responses are mediated by TLR2. It is generally accepted that TLR binding to microbes occurs at the cell surface but this has not been directly demonstrated for human DCs. We show here that TLR2 and TLR4 are expressed inside DCs in an abundant tubulovesicular pattern with a focus of intense staining adjacent to the nucleus. In contrast, there was no detectable expression on the cell surface. TLR2 and TLR4 were readily found both intracellularly and on the surface of monocytes. They were shown to be closely associated with the Golgi complex and colocalized with alpha-tubulin, displaying a high focal concentration at the microtubule organizing centre. Alignment of TLR2 and TLR4 with microtubules was observed, suggesting that microtubules serve as transport tracks for TLR vesicles. Depolymerization of the microtubule network disrupted the intracellular expression of TLR2 and TLR4 and profoundly inhibited interleukin-12 (IL-12) production in response to Neisseria meningitidis but did not prevent phagocytosis. These data are consistent with the bacterial signalling through TLR2 and TLR4 required for IL-12 production occurring inside DCs after phagocytosis.
微生物对树突状细胞（DCs）的激活是由包括Toll样受体（TLR）在内的模式识别受体介导的。细菌脂多糖通过TLR4起作用，而肽聚糖和脂蛋白反应则由TLR2介导。人们普遍认为TLR与微生物的结合发生在细胞表面，但这尚未在人DCs中得到直接证实。我们在此表明，TLR2和TLR4以丰富的管状小泡模式在DCs内部表达，在细胞核附近有一个强烈染色的焦点。相比之下，在细胞表面未检测到表达。TLR2和TLR4在单核细胞的细胞内和表面都很容易找到。它们被证明与高尔基体复合体密切相关，并与α-微管蛋白共定位，在微管组织中心显示出高焦点浓度。观察到TLR2和TLR4与微管对齐，表明微管作为TLR囊泡的运输轨道。微管网络的解聚破坏了TLR2和TLR4的细胞内表达，并显著抑制了对脑膜炎奈瑟菌的白细胞介素-12（IL-12）产生，但不阻止吞噬作用。这些数据与吞噬作用后DCs内部发生的IL-12产生所需的通过TLR2和TLR4的细菌信号传导一致。
