Department of Surgery, University of Pittsburgh, Pittsburgh, PA 15213, USA.
J Immunol. 2013 May 15;190(10):5152-60. doi: 10.4049/jimmunol.1300496. Epub 2013 Apr 5.
The morbidity associated with bacterial sepsis is the result of host immune responses to pathogens, which are dependent on pathogen recognition by pattern recognition receptors, such as TLR4. TLR4 is expressed on a range of cell types, yet the mechanisms by which cell-specific functions of TLR4 lead to an integrated sepsis response are poorly understood. To address this, we generated mice in which TLR4 was specifically deleted from myeloid cells (LysMTLR4KO) or hepatocytes (HCTLR4KO) and then determined survival, bacterial counts, host inflammatory responses, and organ injury in a model of cecal ligation and puncture (CLP), with or without antibiotics. LysM-TLR4 was required for phagocytosis and efficient bacterial clearance in the absence of antibiotics. Survival, the magnitude of the systemic and local inflammatory responses, and liver damage were associated with bacterial levels. HCTLR4 was required for efficient LPS clearance from the circulation, and deletion of HCTLR4 was associated with enhanced macrophage phagocytosis, lower bacterial levels, and improved survival in CLP without antibiotics. Antibiotic administration during CLP revealed an important role for hepatocyte LPS clearance in limiting sepsis-induced inflammation and organ injury. Our work defines cell type-selective roles for TLR4 in coordinating complex immune responses to bacterial sepsis and suggests that future strategies for modulating microbial molecule recognition should account for varying roles of pattern recognition receptors in multiple cell populations.
与细菌败血症相关的发病率是宿主对病原体的免疫反应的结果,而这些反应依赖于模式识别受体(如 TLR4)对病原体的识别。TLR4 表达于多种细胞类型,但 TLR4 的细胞特异性功能如何导致整合的败血症反应的机制仍不清楚。为了解决这个问题,我们生成了骨髓细胞(LysM-TLR4KO)或肝细胞(HCTLR4KO)特异性缺失 TLR4 的小鼠,然后在盲肠结扎和穿刺(CLP)模型中确定了生存、细菌计数、宿主炎症反应和器官损伤,同时使用或不使用抗生素。在没有抗生素的情况下,LysM-TLR4 对于吞噬作用和有效的细菌清除是必需的。生存、全身和局部炎症反应的程度以及肝损伤与细菌水平有关。HCTLR4 对于从循环中清除 LPS 是必需的,而 HCTLR4 的缺失与巨噬细胞吞噬作用增强、细菌水平降低以及在没有抗生素的 CLP 中生存率提高有关。CLP 期间给予抗生素揭示了肝细胞 LPS 清除在限制败血症引起的炎症和器官损伤中的重要作用。我们的工作定义了 TLR4 在协调对细菌性败血症的复杂免疫反应中的细胞类型选择性作用,并表明未来调节微生物分子识别的策略应该考虑到模式识别受体在多种细胞群体中的不同作用。