感染弓形虫小鼠脾脏CD4+CD25+T细胞的变化

目的 观察小鼠感染刚地弓形虫后脾脏CD4⁺CD25⁺调节性T细胞的动态变化。 方法 将28只雌性C57BL/6小鼠随机分为4组，其中3组每鼠腹腔接种弓形虫速殖子悬液200 μl（含弓形虫速殖子5×10⁴个/ml），对照组腹腔接种灭菌PBS 200 μl。分别于弓形虫感染后第2、4和6天取脾，制成单个核细胞，用实时荧光定量PCR检测脾CD4⁺ T细胞Foxp3基因表达水平，流式细胞仪检测脾CD4⁺CD25⁺调节性T细胞占CD4⁺ T细胞的比例，并对CD4⁺CD25⁺调节性T细胞和CD4⁺ T细胞进行绝对计数。 结果 感染后第4和6天，小鼠脾脏CD4⁺ T细胞Foxp3 mRNA相对表达水平分别为 1.89±0.23和1.79±0.24， 均显著高于正常水平（1.00±0.12）（P＜0.01）；CD4⁺CD25⁺调节性T细胞占CD4⁺ T细胞的比例从感染后第2天（15.07%±2.73%）开始上调（P＜0.05），至感染后第4 和6天分别为24.29%±3.19%和19.80%±2.66%，均明显高于正常水平（11.58%±2.04%） （P＜0.01）；脾脏CD4⁺ T细胞占脾细胞的比例及其绝对数量均从感染后第2 天开始降低，至感染后第6 天分别降至5.49%±1.71%和（1.71±0.44）×10⁶ （P＜0.01）。 结论 弓形虫感染导致小鼠脾脏CD4⁺CD25⁺调节性T细胞占CD4⁺ T细胞的比例上调，而脾脏CD4⁺ T细胞的显著减少是促成比例上调的主要原因。

Changes of CD4+CD25+ T Cells in the Spleen of Mice Infected with Toxoplasma gondii

OBJECTIVE: To observe the changes of CD4+CD25+ regulatory T cells in the spleen of mice infected with T.gondii. METHODS: Twenty-eight female C57BL/6 mice were randomly divided into four groups. Three groups of mice were inoculated intraperitoneally with 10(4) tachyzoites in 200 microl sterile PBS. At 2, 4 and 6 days post-infection, the spleens were removed. The expression level of Foxp3 mRNA in splenic CD4+ T cells was quantitated by real-time PCR. The percentage of CD4+CD25+ regulatory T cells in CD4+ T cells was determined by flow cytometry, and the absolute numbers of splenic CD4+CD25 - regulatory T cells and CD4+ T cells were assessed. The fourth group was injected intraperitoneally with 200 microl sterile PBS as control. RESULTS: The relative mRNA level of Foxp3 in splenic CD4+ T cells at day 4 (1.89+/-0.23) and day 6 (1.79+/-0.24) post-infection was significantly higher than control (1.00+/-0.12) (P< 0.01). After an initial up-regulation at 2 days post-infection (15.07%+/-2.73%) (P<0.05), the proportion of CD4+CD25+ regulatory T cells in CD4+ T cells at day 4 (24.29%+/-3.19%) and day 6 (19.80%+/-2.66%) post-infection was significantly higher than control (11.58%+/-2.04%) (P<0.01). At day 6 post-infection, both the percentage of splenic CD4+ T cells in splenocytes(5.49%+/-l.71%) and absolute number of CD4+ T cells (1.71+/-0.44)x106 greatly decreased(P<0.01). CONCLUSION: The proportion of splenic CD4+CD25+ regulatory T cells in CD4+ T cells has been up-regulated following T. gondii infection, which is mainly due to a great reduction of CD4+ T cells in the spleen.