[Effects of external systemic irradiation on changes in immunoreactivity of radiolabeled monoclonal antibody]

Effects of external systemic irradiation on changes of immunoreactivity by radiolabeled monoclonal antibody administrated intravenously to the nude mice were pursued with the method of cell binding assay in vitro. Enhancement of tumor localization and biodistribution of radiolabeled antibody following systemic irradiation were performed in tumor bearing mice. Results obtained were as follows: 1) Immunoreactivity of monoclonal antibody administrated to the nude mice showed the tendency of a gradual fall in comparison with that of pre-administrated. While there found to be no changes of immunoreactivity preserved 37 degrees C in vitro. 2) Systemic irradiation could prevent immunoreactivity of post-administrated antibody from falling gradually, and there found to be dependent upon a dose of irradiation. 3) In an animal model tumor localized activity was significantly made higher than in the not irradiated control group dependent upon a dose of irradiation and tumor to tissue ratio was in the same way. 4) These results indicated that external systemic irradiation for tumor bearing mice would also be beneficial for practical use and clinical application of radiolabeled monoclonal antibodies, besides contributed to the improvement of systemic irradiation-bone marrow transplantation therapy.