γ射线照射后小鼠CD4＋CD25＋调节性T细胞的变化及其意义

Changes and significance of CD4 ＋ CD25 ＋ regulatory T cells in γ-ray irradiated mice

目的观察γ射线照射对小鼠CD4＋CD25＋调节性T细胞（Tregs）亚群的影响，探讨辐射诱发的免疫损伤作用机制。方法C57BL／6小鼠经6Gyγ射线照射后1～28d取胸腺、脾脏称重并计算脏器系数，测量外周血WBC总数，流式细胞仪检测外周血和脾脏CD4＋T细胞、Tregs细胞亚群的变化。结果照射后1d，胸腺和脾脏系数即明显下降，7d降至最低，至照后28d仍未恢复到对照组水平。WBC于照后1—7d持续降至最低，14d开始恢复，至28d仍显著低于对照组。外周血CD4＋T细胞在照后1d-过性降低后逐渐增高，照后28d基本接近对照水平；脾脏CD4＋T细胞在照后7d虽略有降低，但在14和28d基本维持在对照水平。外周血Tregs细胞在照后1d即开始升高，7d达峰值，14和28d仍明显高于对照组；脾脏Tregs于照后1d即显著增至最高，而后缓慢降低，至照后28d出现有统计学意义的降低（t=2．731，P〈0．05）。结论小鼠经6Gyγ射线全身照射后胸腺和脾脏免疫组织严重受损，免疫细胞数量减少；而具有免疫抑制作用的Tregs细胞比例照后明显增高，揭示该亚群与辐射所致的小鼠免疫功能受抑和免疫调节失衡密切相关。

Objective To observe the effect of γ-ray irradiation on CD4 ＋ CD25 ＋ regulatory T ceils （Tregs）, and to investigate the mechanism of immune injury induced by irradiation. Methods The thymus and spleen of C57BL/6 mice were taken and weighted 1-28 d after γ-ray irradiation, and the organ coefficients were calculated. The amount of mouse peripheral WBC measured, CD4 ＋ T cells and Tregs in peripheral and splenic were analyzed by flow cytometry. Results Coefficients of mouse thymus and spleen decreased significantly 1 d post irradiation, and reached to the bottom at 7 d. Coefficients did not recover to control level 28 d after radiation. Peripheral WBC continuously decreased and reached the bottom at 7 d, and did not recover to control level up to 28 d postirradiation. Peripheral CD4 ＋ T lymphocyte temporally reduced at 1 d, while it increased at 7 d, and it approached to control level at 28 d after radiation. Splenic CD4 ＋ T cells slightly reduced at 7 d however, they basically maintained as the same level as control 14 d and 28 d after radiation. Peripheral Tregs ascended at 1 d and reached the peak at 7 d, and reduced at 14 d and 28 d postirradiation, although they still were significantly higher than those of control group. At the same time, splenic Tregs increased significantly and achieved peak value at 1 d, and then gradually decreased and reached the minimum at 28 d after irradiation, which were significantly lower than those of control group（t = 2.731, P 〈 0.05）. Conclusions Mouse thymus and spleen were injured severely, and the number of immunocytes decreased after 6 Gy whole body γ-ray irradiation. However, Tregs with immunosuppressive action increased significantly postirradiation, revealing that Trcgs were closely correlated with immune function depression and immunomodulation imbalance induced by ionizing radiation.