EXTRACORPOREAL IMMUNOADSORPTION OF 125-I-LABELED MONOCLONAL-ANTIBODY L6

The aim of this study was to investigate the effect of extracorporeal immunoadsorption (ECIA) on the biokinetics of the intact L6 mouse mono clonal antibody in a rat model. 125I-labeled L6 and 125I-labeled bioti nylated L6 antibodies were used. A model with human lung adenocarcinom a tumors implanted under the kidney capsule and intramuscularly in ath ymic rats, was used to investigate to what extent the ECIA procedure c ould improve the detectability of tumors in well vascularized tissues. The ECIA procedure was performed 24 or 48 hours after the injection o f the antibodies. The study showed that the plasma activity concentrat ion was reduced by 80 - 85 % by the ECIA procedure and the whole body activity was reduced by 30 - 45 %. The tumor-to-plasma ratio was incre ased by 5.3/6.8 times for intramuscular (IM) tumor/subrenal (SR) tumor , and tumor-to-organ ratios were increased by 3.1/4.5 times in liver, 3.4/4.4 times in kidney, 2.1/2.6 times in lung, 3.1/3.1, times in bone marrow and 2.1/3.0 in muscle when ECIA was started 24 hours after the injection of the antibodies. The detectability, i.e. the contrast in the scintillation camera images was improved by 40 % (from 1.04 to 1.4 6) by the ECIA, and tumors under the kidney capsule were clearly visua lized after the procedure. These results show the potential of using E CIA in combination with radio-labeled monoclonal antibodies to increas e the detectability of tumors.