中文摘要：

目的探讨小剂量X射线照射对体外不同培养时间的人外周血树突状细胞（dendriticcell，DC）抗原递呈及白介素-12（IL-12）分泌的影响。方法分离人外周血单个核细胞（PBMC），以人粒-巨细胞集落刺激因子（GM-CSF）及IL-4等诱导分化成DC。实验分为3组，A组：DC培养至第2天接受X射线照射；B组：DC培养至第6天接受X射线照射，A、B组受照剂量均为0．05、0．1、0．2和0．5Gy；C组：即对照组，为同期培养的未受x射线照射的DC细胞。各组DC培养至第8天时，以DC致敏T细胞，CCK-8（cellcountingkit-8）法检测混合淋巴细胞反应（mixedlymphocytereaction，MLR），以评估抗原递呈能力；MTT法检测致敏T细胞杀伤人肺腺癌A549细胞；酶联免疫吸附试验（ELISA）检测DC细胞培养液中IL-12水平。结果0．2、0．5Gy照射后的DC抗原递呈能力，A组显著低于对照组（t=2．79和3．71，P〈0．05），B组显著高于对照组（t=3．60和3．11，P〈0．05）；检测致敏T细胞对人肺腺癌A549细胞的增殖抑制能力，与对照组相比，A组抑制A549增殖能力减弱（t=2．89和2．91，P〈0．05），B组抑制A549增殖能力明显增强（t=2．91和2．82，P〈0．05）；A组IL-12分泌量下降（t=4．44和6．93，P〈0．05），而B组明显上升（t=3．51和4．12，P〈0．05）。结论DC在培养早期阶段接受0．5Gy以下的x射线照射，会降低抗原递呈能力及致敏T细胞杀伤A549能力，在培养阶段的后期给予此剂量照射则会增强。

英文摘要：

Objective To explore the effects of low dose X-ray irradiation on the ability of antigen presentation and IL-12 secretion in human dendritic cells that had been cultured for different time in vitro. Methods The human peripheral blood mononuclear cells （PBMC） were collected and differentiated to dendritic cells （DCs） by rhGM-CSF and rhlL-4 treatment in vitro. The DCs were divided into 3 groups, group A ： DCs were cultured for 2 d and then irradiated with 0. 05, 0. 1, 0.2 and 0. 5 Gy X-rays ; group B ： DCs were cultured for 6 d and then irradiated as above; group C： DCs were cultured without irradiation. At 8 d of cell culture, the DCs were applied to activate T cells and CCK-8 was used to detect MLR （ mixed lymphocyte reaction） , and the antigen presentation ability of DCs was evaluated. MTT assay was also used to test the cell-killing effect of the activated T-cells on A549 cells. IL-12 in the cuhure medium of DCs was detected by ELISA. Results After irradiation with 0. 2 and 0. 5 Gy X-rays, the antigen presentation ability of DCs was decreased in group A （ t = 2. 79 and 3.71, P 〈 0. 05 ） , but significantly increased in group B （ t = 3.60 and 3.11, P 〈 0. 05）. The ability of the T cell activation was detected and the proliferation of A549 cells was slightly inhibited by the DCs in group A （t =2. 89 and 2. 91, P 〈0.05） , but was obviously inhibited by the DCs in group B （t = 2. 91 and 2. 82, P 〈 0. 05）. Meanwhile, the level of IL-12 was dramatically decreased in group A （ t = 4.44 and 6.93, P 〈 0. 05 ） , but was increased in group B （ t = 3.51 and 4. 12,P 〈 0.05 ）. Conclusions The abilities of antigen presentation and proliferation inhibitionof DCs could be down-regulated by low dose（ 〈 0.5 Gy） of X-ray irradiation at the early stage of DCs, but was up-regulated at the late stage of DCs culture.