[Selective accumulation of 131I-labeled IKO-1 monoclonal antibodies in the tissues of mouse L 1210 lymphoid leukemia].

Monoclonal antibodies (MCA) ICO-1 of IgG3 isotype against 1a-like human antigens were labelled with 131I using chloramine T; a radionuclide-bound fraction was isolated by radiochromatography. Basing on the results of assessment of complement-dependent cytotoxicity against lymphocytes from the lymph nodes of BDF1 mice a conclusion was made that MCA immunological reactivity changed slightly after radionuclide tracer administration. In vitro experiments with a panel of normal and malignant cells showed 131I-MCA binding with cells of mouse lymphoid leukemia L1210 and hemocytoblastosis La as well as with spleen and lymph node normal lymphocytes. During in vivo experiments 131I anti-la MCA at a dose of 30 micrograms (specific activity of 32.10(10) Bq/mmol) was administered intravenously to BDF1 mice with transplantable lymphoid leukemia L1210. Radiometry of the organs 24 h after administration of antibodies showed their accumulation in a solid tumor localized on intestinum tenue mesenteriale. The ratio of concentrations of labelled antibodies (in % of the administered amount per 1 g) of tumor/blood was 2.4, that of tumor/liver--4.5. For normal nonimmune 125I-IgG this rate was 0.4 and 0.7, respectively. A high level of MCA in the blood is a factor decreasing MCA diagnostic potentialities. The use of F(a, b)-fragments may considerably decrease the role of this factor. The data obtained suggest a possibility of the use of MCA ICO-1 for in vivo radioimmunoassays of some hematological tumors.