Evaluation of the immunological properties and safety of 99m Tc-C 50 CEA McAb labelled by 2-IT was reported. C 50 was modulated chemically by 2-IT and labelled by 99m Tc with stannous reduction. The immunological activity

stability and safety were studied

and radioimmunoimaging were performed in human colon tumor bearing mice. The results showed that the immunological activity

the best labelling rate of chromatography and colloid inclusion were 40.2%-73.2%

94.1% and 3.8% respectively

and radiochemicl purity maintained over 90% within 12h after labelling. Labelling products was pyogen free and no toxicity was found. Radioactivity was highly accumalated at tumor site of 6h after injection human colon tumor bearing nude mice

T/NT ratio was 3.46-4.68 at 24h after 99m Tc-C 50 injection. All the findings suggested that preconditioning with 2-IT to C 50 can improve labelling of 99m Tc

and minimize the injury of protein. The labelling method is simple and safe

and can be effectively used for clinical study.