Localizing properties of antibody to alphafetoprotein (AFP) to AFP-producing tumor cells.

Studies have been undertaken to clarify the localizing properties of radioactively labeled antibody to AFP using ascitic hepatoma cells which produce AFP. In the in vitro studies, radioantibodies to AFP were incorporated into the AFP-producing cells, even though excess antigen existed in the medium and the antibodies remained on the cell surface for a long time. In the in vivo studies, the radioantibodies to AFP bound to the AFP-producing cells, especially those producing high levels of AFP (AH66). Tumor localization by scintigraphy was clearer with the AH66 hepatoma than with the AH41C hepatoma, which produces less AFP. The presence of large amounts of AFP in the circulation did not prevent the tumor radioimmunodetection. It is suggested that radioantibodies to AFP bind to the AFP-producing cells despite the presence of large amounts of AFP in the circulation or in ascitic fluid.