钆标记单克隆抗体片段对荷瘤裸鼠MR免疫成像的研究

Experimental studies on Gd labelled F(ab)′_2 fragments of anti colorectal carcinoma antibodies MR in nude mice models with LS-174T tumor

目的 探索标记钆 (Gd)对抗体活性的影响并分析MR增强效果。方法 (1 )取 2 0只裸鼠制作荷大肠癌动物模型 ;(2 )将C DTPA (DTPA环二酸酐 )与抗人大肠癌 (CL 3 )单克隆抗体片段F(ab)′2 按C/P (DTPA环二酸酐与抗体片段的摩尔比值 ) =2∶1和 5∶1分A、B两组 ,偶联制备Gd F(ab)′2 DTPA ;(3 )MR扫描 :1 8只裸鼠随机分 3组 ,作平扫和增强扫描 ,2只作瘤内直接注射 ,取T1WI信号强度数据 ,进行相对标准化处理。结果 标记后A、B两组抗体免疫结合率分别为 74%和62 %。增强扫描 ,肿瘤均有轻度强化 ,B组 (3 1 67± 1 1 2 )比A组 (2 4 45± 1 92 )明显。结论 随着C/P的增加 ,标记抗体片段的活性下降 ,但MR增强效果有所增加且F(ab)′2 DTPA Gd的增强作用具有特异性。

Objective To evaluate the enhancing effect of MRI with Gd DTPA F(ab)′ 2 in nude mice models with LS 174T tumor, and to investigate the influence of Gd labeling on the immunocompetence of the fragments (ab)′2 of CL 3. Methods (1)Antibodies and tumor models preparation: Monoclonal antibodies (McAb) fragment F(ab)′ 2 against LS 174T colonic adenocarcinoma cell were prepared with hybridoma cell CL 3. Twenty BALB/C nude mice were used as tumor models by subcutaneous injection of LS 174T cells. (2)Gd 3+ Labelling: DTPA anhydride and F(ab)′ 2 fragments were conjugated. Two groups were classified: group A, with C/P=2∶1; group B, with C/P=5∶1. Then, Gd was added into DTPA F(ab)′ 2 solution. Gd DTPA F(ab)′ 2 was formed. Free Gd 3+ and DTPA were removed by dialysis. Purified Gd DTPA F(ab)′ 2 was available. (3) MR scanning techniques: MRI was performed with a GE Signa Horizon LX MR scanner. The nude mice were immobilized and divided into three groups: routine plain scan group, enhanced scan group A(C/P=2∶1)and group B(C/P=5∶1). Results When pH=8.0 ,[F(ab)′ 2]=4.6 mg/ml, and C/P=2∶1 or C/P=5∶1, immuno conjugated rates of group A and B were 74% and 62%, respectively. Immunocompetence of fragment F(ab)′ 2 reduced approximately 12% when C/P increased from 2∶1 to 5∶1.The enhancing effects of two groups of nude mice were both poor, and that of group B(C/P=5∶1) was better than that of group A(C/P=2∶1). Conclusion While C/P increasing, immunocompetence of fragment F(ab)′ 2 reduced, and the enhancing effects of group B was better than group A. The enhancing effect of Gd DTPA F(ab)′ 2 was tumor specific.