肺炎衣原体感染对小鼠体内Th1/Th2影响的初步研究

Effects of Chlamydia pneumoniae infection on immune system response in mice

目的通过复制小鼠感染肺炎衣原体的动物模型,检测接种后小鼠体内Th1/Th2平衡改变,对感染后小鼠机体免疫状态进行初步研究。方法96只小鼠随机分为实验组和对照组,实验组采用鼻内接种途径建立肺炎衣原体感染小鼠模型,对照组接种二磷酸蔗糖(2SP)无菌缓冲液。分别在接种后的第1,3,5,7,14,21,28和42d,各处死6只动物,收集标本。观察记录肺组织病理,用ELISA法检测血清中白细胞介素-4(IL-4)和γ干扰素(IFN-γ)表达,用流式细胞术检测小鼠脾淋巴细胞中Th1和Th2细胞,计算Th1/Th2比值。结果感染肺炎衣原体小鼠的肺组织病理表现多为局灶性肺炎,14d后单核细胞和淋巴细胞含量增多,并伴不同程度成纤维细胞增生。与对照组相比,鼻内接种肺炎衣原体后24h,可见小鼠血清IL-4水平升高,第3d时浓度达到最高(24·38±2·52)pg/mL。持续至第7d,而后恢复到基线水平。血清IFN-γ在接种后24h即达到峰值(23·00±5·15)pg/mL,此后浓度逐渐下降。对照组小鼠Th细胞功能上以Th1细胞占优势,接种肺炎衣原体后Th1/Th2比值明显降低,细胞分类向Th2细胞漂移。第3d时,Th1/Th2比值降到最低值。实验组小鼠在感染后所检测42d内,所有Th1/Th2比值均明显低于对照组(P<0·01)。结论小鼠感染肺炎衣原体后,细胞分类向Th2细胞漂移。宿主肺部炎症病变加重与早期Th1细胞免疫活性受到抑制有关。与外周血IFN-γ/IL-4比值相比,流式细胞术检测细胞内IFN-γ/IL-4,更能代表Th1/Th2极化状态。

Objective To evaluate the infection kinetics and assess the distribution characteristics of Th1-type cytokine（ interferon-γ, IFN-γ） and Th2-type cytokine （ interleukin-4, IL-4） in the serum and Th1/Th2 reactions in the spleen cells in Icr mice inoculated with Chlamydia pneumoniae （ C. pneumoniae ）, therefore to gain insight into the possible role of the systemic Th1/Th2 cell-mediated immune response in the pathogenesis of C. pneumoniae infection. Methods 96 Icr mice were randomly divided into two groups：the experimental group intranasally inoculated with C. pneumoniae suspended in 2-sucrose phosphate（2SP） transport medium, and the control group inoculated with 2SP transport medium only. The pathological changes of lung tissue were examined under light microscopy.The concentrations of IFN-γ and IL-4 in the serum were measured with enzyme linked immuno-sorbent assay （ELISA）. The T-helper cell cytokine profiles of splenocytes were analyzed by flow cytometry（ FCM ）. Results The lung pathology was characterized by patchy interstitial pneumonitis predominantly infiltrated with neutrophil leukocyte in the early（7 days） and with lmyphocytes in the later stage （ 14 days later） of infection. After 24 hours＇ infection, the concentration of IL-4 in serum began to increase. The peak mean concentration of IL-4 was （24.38 ± 2.52）pg/mL on day 3 and lasted to day 7,then decrease to the level of base line. IFN-γ/ level in experimental group increased to （23.00 ± 5.15 ）pg/mL after 24 hours after inoculation, then decreased. Thl immuneresponse was predominant in the control group. However, ＇after C. pneumoniae inoculation, the value of Th1/Th2 decrease to valley on day 3. Th1/Th2 were significantly lower than those in the control group and lasting for the whole infection period （ all P 〈 0.01 ）. Conclusions After C. pneumoniae infection, cell immune respone switched to Th2 type immune response. The exacerbatod inflammation in lung of host resulted from Thl cell immune suppressed in the early stage. Compared with the ratio of IFN-y to IL-4 in the senun, intraeellular cytokines analyzed by flow cytometry stand for Th1/Th2 polarization.