中文摘要：

目的 探讨紫外线诱导的凋亡细胞是否具有旁观者效应。方法 将Molt=4细胞分为阴性对照组、DID对照组、空白对照组和细胞密度分别为2×10^5／ml和8×10^5／ml的两个实验组。每个实验组细胞被平分为两部分：一部分作为效应细胞，被标记示踪剂DID染料并予以UV照射40s；另一部分作为旁观者细胞，不经任何特殊处理。细胞联合培养共24h，每4h收获1次。运用Annexin V—FITC／PI法检测旁观者细胞的细胞凋亡率，激光共聚焦显微镜检测旁观者细胞的形态学变化。结果 阴性对照组、DID对照组和空白对照组在0、4、8、12、16、20和24h各个时间点细胞凋亡率均小于5％。2×10^5／ml实验组旁观者细胞凋亡率在0～24h分别为3．47％、4．58％、7．32％、10．41％、14．82％、19．37％和25．66％。8×10^5／ml实验组旁观者细胞凋亡率在相应时间点分别为3．76％、5．77％、10．17％、14．71％、18．92％、32．28％和38．90％。与对照组相比，实验组旁观者细胞凋亡率随时间的延长而明显升高，且旁观者细胞凋亡率随细胞密度增高而增加。对旁观者细胞进行激光共聚焦显微镜检测，发现一些经典的凋亡和坏死表现，如细胞染色体浓集、磷脂酰丝氨酸翻转、凋亡小体形成、细胞崩解等。结论 经紫外线照射的Molt-4细胞对旁观者细胞具有旁观者效应，且该效应与细胞密度相关。

英文摘要：

Objective To investigate the bystander effect of ultra-violet （UV）-induced apoptosis of MOLT-4. Methods Two experimental groups were set up, in which Molt-4 cells were cultured and treated at two densities： 2 × 10^5/ml and 8 × 10^5/ml. In the two experimental groups, part of the cells was labeled with DID and exposed to UV for 40 s serving as effect cells; the other cells were left untreated and used as bystander cells. The cells were co-cultured and harvested at a 4-h interval over a period of 24 h. Annexin V-FITC/PI assay was used to evaluate the bystander effect in bystander cells. Laser confocal microscopy was used to observe the morphologic changes of the bystander cells. Results The apoptosis rate in the bystander cells was increased over time. In 2× 10^5/ml experimental group, the apoptosis rate was 3.47%, 4.58%, 7.32%, 10.41%, 14.82%, 19. 37% and 25. 66% respectively at 0, 4, 8, 12, 16, 20 and 24 h; In 8 × 10^5/ml experimental group, it was 3.76%, 5.77%, 10.17%, 14.71%, 18.92%, 32.28% and 38.90% respectively at the same time point. Under laser scanning confocal microscopy, the bystander cells showed some typical characteristics of apoptosis such as condense chromosome, phosphatidylserine transferring and formation of apoptotie bodies. Conclusion Obvious bystander effect exists in non-irradiated bystander Molt-4 cells when co-cultured with UV exposed cells.