中文摘要：

目的探讨体内转录法合成的小干扰RNA（siRNA）对淋巴细胞共刺激分子CD40基因表达的影响。方法设计并合成4条siRNA（si40-1、si40-2、si40-3、si40-4），在阳离子脂质体的介导下转染SD大鼠淋巴细胞。于转染48h收集细胞，半定量RT-PCR方法检测CD40mRNA，流式细胞仪检测CD40表达。结果流式细胞仪检测显示，si40-1、si40-2、si40-3、si40-4组的CD40表达抑制率分别为（21．10±1．54）％、（74．40±1．03）％、（41．80±0．86）％、（36．02±0．76）％，均明显高于空白对照组[（3．01±0．82）%]（P〈0．01），其中以si40-2的CD40抑制作用最强。半定量RT-PCR检测显示，与空白对照组比较．4组siRNA转染后淋巴细胞CD40mRNA均受到明显抑制伊〈0．01）．其中si40-2组的抑制作用最明显。结论sIRNA可特异性抑制淋巴细胞共刺激分子CD40基因的转录和表达，从而为进一步研究siRNA在移植免疫耐受及防治移植物抗宿主疾病（GVHD）方面的应用提供了理论和实验基础。

英文摘要：

Objective To investigate the expression of CD40 costimulatory molecule on rat lymphocytes inhibited by siRNA. Methods Four different siRNAs （si40-1 ,si40-2,si40-3,si40-4） were designed and synthysized followed by transfection into freshly isolated rat lymphocytes with cationic liposome. 48 h after transfection, the changes of CD40 expression were detected by flow cytometry, and the changes of CD40 mRNA levels were determined by semi-quantitative RT-PCR. Results si40-1, si40-2, si40-3 and si40-4 reduced CD40 expression by （21.10 ± 1.54）%, （74.40 ± 1.03）%, （41.80 ± 0.86）% and （36.02 ± 0.76）% respectively, as identified by flow cytometry, compared with the control [（3.01 ± 0.82）%]（P 〈 0. 01 ）. si40-2 was the most potent inhibitor. Semi-quantitative RT- PCR assay indicated CD40 mRNA levels were inhibited after transfection, at least 4 folds in si40-2 group at 48 h post transfection compared with the control （P 〈 0.01 ）. Conclusion Four different siRNAs reduce the expression of CD40 and the CD40 mRNA level via costimulatory molecule blockade, which may provide theoretical and reaching for further study on graft versus host disease （GVHD） after allogeneic bone marrow transplantation.