γ射线照射诱导胸腺中调节性T细胞表型改变的研究

目的： 分析γ射线照射对小鼠胸腺淋巴细胞及调节性T细胞亚群数量和表型的影响。方法：用2 Gy γ射线全身照射小鼠，同时设未照射对照组。在照射后1、4和10 d分离胸腺中的淋巴细胞，计数后利用流式细胞仪分析CD4+ T细胞、CD4+FOXP3+CD25+ Treg细胞亚群的比例以及Treg细胞中CD39、CD103等表型因子的表达水平。结果：受照后不同细胞亚群的时间响应具有显著差异。与对照组比较，胸腺细胞和CD4+CD8- T细胞数显著减少(P<0.05)，在照射后4 d达到最低水平(P<0.05)，照射后10 d明显恢复；Treg细胞在照射后1和4 d细胞存活比例与对照组比较无显著差异，而在照射后10 d显著减少(P<0.05)；同时CD4+FOXP3+CD25+ Treg/CD4+ T比值则呈现先上升后下降的现象。照射4 d后CD39+ Treg细胞比例和CD39的平均荧光强度 (mean fluorescence indensity，MFI)均显著增加(P<0.05)，CD103+ Treg细胞比例增加但CD103的MFI却减小(P<0.05)。结论：γ射线照射后初期，Treg细胞较其他胸腺细胞具有辐射抗性，机体主要呈现免疫抑制状态，其中CD39和CD103是辐射诱导Treg细胞改变的主要表型因子，提示可能介导Treg细胞发挥抑制作用。

Phenotypic changes of regulatory T cells in thymus induced by ionizing radiation

OBJECTIVE: To analyze the radiation-influence induced changes of the number and phenotype of the thymocytes and its regulatory subsets in mice. METHODS：Mice were exposed to 2 Gy 60Co γ-ray in a whole body manner，and thymocytes were separated and counted in 1，4 and 10 d after irradiation. The percentage of CD4+ T and reg in thymocytes and the expression of CD39，CD103 in Treg were analyzed using FACS. RESULTS：There were differences in time-response to radiation. The thymocyte and CD4SP T cell numbers were decreased significantly after whole body irradiation and reached a minimum in 4 days，but recovered clearly after 10 days. However the Treg cell decreased in a manner of non-statistical difference in 4 days，but decreased significantly in 10 days. The percentage of Treg increased first then decreased in a time-response manner. The percentage of CD39+ Treg cell and MFI of CD39 were increased after 4 days’ irradiation. The percentage of CD103+ Treg cell was also increased，however its MFI was deceased after 4 days’ irradiation. CONCLUSION：Treg cells were more resistant to radiation than other thymocytes，resulting in the immune suppression of whole body. The expressions of CD39 and CD103 were differentially regulated by radiation and may play an important role in mediating suppressive function of Treg.