Toll样受体2/4-核因子κB信号通路在人结核分枝杆菌侵入小鼠树突细胞2.4中的作用

目的：研究人结核分枝杆菌侵入抗原提呈细胞后诱导树突细胞（DC）成熟的机制。方法：选择小鼠DC2.4细胞株为抗原提呈细胞的效应细胞，建立人结核分枝杆菌H37Rv株的细胞混合培养模型。在不同混合培养时段，采用实时荧光定量PCR检测DC2.4细胞Toll样受体2（TLR2）、TLR4 mRNA的表达量；蛋白质印迹法检测DC的核因子κB(NF-κB)p65蛋白的表达；免疫酶联吸附试验定量检测DC产生α肿瘤坏死因子（TNF-α）的水平；采用间接免疫荧光法和流式细胞术检测DC2.4表面CD80和CD86的表达情况。结果：H37Rv与DC2.4共培养2 h后开始有细菌侵入；共培养 6、8、10、12 h后，细菌侵入率分别为(37.9±5.6)%、(512±7.6)%、(57.2±8.9)%、(639±12.4)%；TLR2、TLR4 mRNA也开始增量，共培养10 h时达高峰，之后开始下降；共培养6 h时，NF-κB p65的表达量明显增高；TNF-α的表达量在共培养6 h开始上调，8 h时达高峰，随后逐渐下降；共培养6 h时，DC2.4表面CD80、CD86表达量明显增高。结论：人结核分枝杆菌侵入DC2.4时，通过激活TLR2/4-NF-κB信号通路，诱导DC成熟，提高其抗原提呈能力。

Role of Toll-like receptor 2/4-nuclear factor-κB signaling pathway in invasion of Mycobacterium tuberculosis to mouse dendritic cells

Objective： To investigate the mechanism of Mycobacterium tuberculosis invasion to mouse dendritic cells (DC).Methods： Mycobacterium tuberculosis strain H37Rv was co-cultured with mouse DC2.4 cells.The mRNA expression of Toll-like receptor 2/4(TLR2/4) in DC2.4 cells was detected by fluorescent quantitative real-time PCR and the protein expression of nuclear factor κB(NF-κB) was assessed by Western blotting.The extracellular concentration of tumor necrosis factor α(TNF-α) was measured by ELISA methods during Mycobacterium Tuberculosis invasion.Indirect immunofluorescent staining and flow cytometry assay were used to detect the expression of CD80 and CD86 on DC2.4 cells before and after invasion.Results： The invasion of Mycobacterium tuberculosis in DC2.4 cells was observed after 2 h of co-incubation.The rates of invasion were (37.9±5.6)%，(51.2±7.6)%，(57.2±8.9)% and（63.9±6.8）% at 6，8，10 and 12 h after co-incubation，respectively.The mRNA expression level of TLR2 /4 was significantly increased at 6 h but decreased at 10 h after co-incubation.The expressions of NF-κB p65 and TNF-α were higher in DC2.4 cells after being invaded by 6，8，and 10 h and then gradually decreased.CD80 and CD86 expression were increased on DC2.4 at 6 h after co-incubation.Conclusion： Invasion of Mycobacterium tuberculosis strain H37Rv to DC might enhance its antigen-presenting function through activation of TLR2/4-NF-kB signaling pathway.