X射线和γ射线预处理对小鼠异基因骨髓移植后造血免疫重建的影响

Effects of X-rays and γ-rays on reconstitution of hematopoiesis and immunity after allogeneic bone marrow transplantation

目的研究X射线和γ射线两种预处理方式造成的损伤程度的差别，以及对造血、免疫重建的影响，确定适用于异基因造血干细胞移植的预处理照射方式。方法对受鼠分别使用直线加速器X射线或60Coγ射线进行致死剂量（总剂量为7．0Gy）全身照射后，给予相同数量供鼠骨髓细胞移植。观察受鼠移植后的生存时间、重要脏器（肝、小肠和肺）病理变化、嵌合率（H-2Kb＋细胞比例）和造血免疫重建状况。结果移植后早期，1射线移植组生存率高于X射线移植组，小肠和肺损伤程度亦较轻。嵌合率γ射线移植组5和10d均高于X射线移植组（t=15．263、3．256，P〈0．05）。γ射线移植组10和20d外周血白细胞计数和淋巴细胞植入率均高于X射线移植组（t=3．624、6．695，P〈0．05）。结论与X射线相比，γ射线照射产生的预处理损伤较轻，可获得较好的造血、免疫重建效果，可提高移植模型的质量和实验的均一性。

Objective To determine the conditioning regimen suitable for mice allogeneic hematopoietic stem cell transplantation （allo-HSCT）. Methods Twelve BALB/c mice were randomly divided into 2 equal groups to undergo X-ray irradiation by linear accelerator at the dose of 7.0 Gy （ pure X-ray group） or 60Co source irradiation at the dose of 7.0 Gy （pure γ-ray group）. Thirty mice were randomly divided into 2 equal groups to undergo X-ray irradiation and then infusion of bone marrow from donor mice via caudal vein （ X-ray ＋ transplantation group） or γ-ray and then infusion of bone marrow via caudal vein （γ-ray ＋ transplantation group）. 3, 5, 7, 10, 15, 20, and 30 d later peripheral blood samples were collected to calculate the number of white blood cells （WBCs） and detect the chimeric rates of lymphoeytes by flow eytometry. 5, 10, and 20 d after irradiation 15 mice were killed with their lung, liver, small intestine, spleen, and femurs taken out to undergo pathological examination. Results The survival rates during the period 5 - 15 days of the γ-ray ＋ transplantation group were all significantly higher than those of the X-ray ＋ transplantation group. The pathological changes of organs of the X-ray ＋ transplantation group were all more severe than those of the γ-ray ＋ transplantation group. Since the fifth day after transplantation cells originating from the donor began to appear in the peripheral blood. The chimeric rate of the γ-ray ＋ transplantation group 10 days after transplantation was （95.53 ±2.57 ） %. The chimeric rates 5, 10, and 20 days after transplantation of the γ-ray ＋ transplantation group were all significantly higher than those of the X-ray ＋ transplantation group （ t = 15. 263,3. 256, P 〈 0. 05 ）. The WBC count of both irradiation groups decreased to the lowest level 5 d later and began to increase 10 days after transplantation and the WBC counts of the γ-ray ＋ transplantation group 10 and 20 days after transplantation were both significantly higher than those of the X-ray ＋ transplantation group （t = 3. 624, 6. 695,P 〈 0. 05）. The chimeric rats of the peripheral lymphoeytes 10 and 20 days after transplantation of the γ-ray ＋ transplantation group were both significantly higher than those of the X-ray ＋ transplantation group （t = 12. 317, 8. 295, P 〈 0.05 ）. The homogeneity rate of transplantation of the γ-ray ＋transplantation group was better than that of the X- ray ＋ transplantation group. Conclusions As a conditioning regimen in allogeneic hematopoietic stem cell transplantation y-ray irradiation causes milder injury and accelerated reconstitution of hematopoiesis and immunity, in comparison with X-ray irradiation.