低剂量辐射对脐血的免疫刺激作用

目的：探讨低剂量辐射对脐血T淋巴细胞膜分子表达，IL－2分泌及LAK细胞体外抗肿瘤活性的影响。方法：新鲜分离的脐血淋巴细胞及LAK前体细胞接受低剂量γ射线照射，分别用直接免疫荧光标记流式细胞术，MTT法及3H-TdR释放实验检测T淋巴细胞膜分子的表达，IL－2分泌的LAK体外杀伤肿瘤靶细胞（K562，HL－60）活性。结果：（1）62mGyγ射线照射后，脐血淋巴细胞CD3，TCR／CD3复合物，CD4，CD8分子表达显著上调，且均在4－24h，人随时间推移而逐步增强，CD4／CD8比值无显著性变化；（2）62mGy γ射线照射后，脐血单个核细胞上清IL－2活性随培养时间推多逐渐增强，不同时间点比较差异均有显著性（P＜0．05）；（3）脐血LAK细胞对K562和HL－60的杀伤活性与成人外周血相比差异无显著性（P＞0．05），接受低剂量辐射的脐血LAK细胞对K562和HL－60的细胞毒性显著高于非照射组（P＜0．01），结论：低剂量辐射可促进脐血T淋巴细胞的成熟，活化和信号的转导及IL－2的分泌，增强脐血LAK杀伤肿瘤靶细胞的细胞毒活性，从而可能在脐血移植中加速免疫功能重建，增强移植物抗白血病效应。

Stimulatory effect of low dose irradiation on immune functions of cord blood

Objective\ To investigate the stimulatory effect of low dose irradiation on immune functions of cord blood and its clinical significance. Methods\ Freshly isolated lymphocytes and LAK cells from cord blood were irradiated with low dose gamma\|rays.The expressions of the membrane molecules of T lymphocytes,the levels of IL\|2 in the supernatant and the cytotoxicity of LAK cells against target tumor cells (K562,HL\|60) were examined by using flow cytometry with direct immunofluorescence,a bioassay based on CTLL cells,which served as target cells,and a 3H\|TdR release assay,respectively. Results\ (1) The proportion of CD3\++,TCR\++/CD3\++,CD4\++,CD8\++ cells increased significantly after low dose irradiation,with the most obvious enhancement noted in the 24 h experimental group.The ratio of CD4 to CD8 showed no significant changes.(2) The biological activity of IL\|2 in the supernatant of cord blood mononuclear cells was enhanced increasingly after low dose irradiation.(3) There was no significant difference in cytotoxicity of LAK cells against target tumor cells between cord blood and peripheral blood ( P >0 05).There was significantly increased cytotoxicity of LAK cells from cord blood against target tumor cells irradiated with low dose gamma\|rays as compared with those of non\|irradiated (All P <0 01). Conclusion\ It is suggested that expedition of maturation,activation,signal transduction and IL 2 secretion of T lymphocytes from cord blood,as well as the enhancement of cytotoxicity of cord blood LAK cells against target tumor cells,which may contribute to intensifying elimination of minimal residue disease,facilitating the reconstruction of immune functions and strengthening the graft\|versus\|leukemia response in cord blood transplantation,can be induced by low dose irradiation.