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

ABSTRACT

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.