沙眼衣原体呼吸道感染诱导γδT细胞在肺组织增殖并产生大量IFN-γ及IL-17

Chlamydia muridarum respiratory tract infection induces the proliferation of γδT cells and the secretion of IFN-γ and IL-17

目的探讨小鼠沙眼衣原体呼吸道感染不同时期γδT细胞的增殖、活化及细胞因子的产生。方法C57BL／6小鼠鼻腔吸入3×10^3IFU（inclusion-forming units）沙眼衣原体小鼠肺炎株（Chlamydia muridarum，Cm）建立小鼠沙眼衣原体肺炎模型。取感染后不同时间点小鼠肺组织进行单个核细胞分离，利用流式细胞术检测小鼠肺CD3^＋TCRγδT细胞百分率，并检测γδT细胞表面分子CD69的表达水平；利用细胞内细胞因子染色技术检测γδT细胞IFN-γ和IL-17的产生。结果一定剂量的Cm经呼吸道感染诱导小鼠衣原体肺炎。与未感染的对照组比较，Cm感染诱导小鼠肺组织γδT细胞百分率及γδT细胞总数逐渐升高，于感染后第7天达到高峰，随后逐渐下降；肺组织γδT细胞表面活化分子CD69表达于感染后第3天达高峰，此后略有降低。Cm感染诱导γδT细胞分泌大量IFN-γ、IL-7，于感染后第3天达到高峰；相比αβT细胞，γδT胞主要在感染早期（感染后前3天）分泌大量IFN-γ和IL-17，而后期CD3^＋CD4^＋T细胞产生IFN-γ和IL-17的能力逐渐高于γδT细胞。结论一定剂量的Cm呼吸道感染可以诱导小鼠γδT细胞在感染局部大量聚集及活化，γδT细胞是宿主抗衣原体免疫应答早期分泌IFN-γ和IL-17的主要细胞类型。

Objective To investigate the proliferation, activation and cytokine production of γδT cells during different periods of Chlamydia muridarum （Cm） respiratory tract infection. Methods C57BL/6 mice were inoculated intranasally with 3 × 10^3 inclusion-forming units （IFU）of Cm strains to induce the murine model of chlamydial pneumonitis. Mononuclear cells were isolated from lung tissue samples col- lected from mice at different time points after infection. Flow cytometry analysis was used to detect the percentages of CD3^＋TCRγδT cells in lung tissues and the expression of CD69 molecule. Intracellular cytokine staining was performed to analyze the secretion of IL-17 and IFN-γ by γδT cells. Results The mouse model of chlamydial pneumonitis was successfully established by intranasal inoculation of C57BL/6 mice with 3×10^3 IFU of Cm strains. Compared with the mice without Cm infection, the percentage and the absolute number of CD3^＋TCRγδT cells in mice lung tissues were significantly increased after Cm infection, the peak of which was reached on the 7th day, followed by a decline. The expression of CD69 molecule on γδT cells isolated from mice lung tissues reached to the highest level on the third day after Cm infection and declined slightly afterwards. Moreover, enhanced secretion of IL-17 and IFN-γ by γδT cells were observed in mice with Cm infection and the highest levels of the two cytokines were detected on the third day after infection. Most of the cytokines （IL-17 and IFN-γ） were secreted by γδT cells rather than by αβT cells in the early stage of Cm infection. However, the CD3^＋CD4^＋ T cells were more capable of producing IFN-γ and IL-17than γδT cells after three days of Cm infection. Conclusion Cm respiratory tract infection could induce the aggregation and activation of γδT cells at the infection site. The γδT cells were the predominant ceils producing IL-17 and IFN-γin the early stage of host anti-chlamydia response.