Abstract
The induction of killer activity following radiotherapy was studied in intracranial tumor-bearing mice. When local 60Co irradiation was administered to intracranial tumor-bearing mice, tumor growth was suppressed and the survival time of the mice was prolonged. The killer activity for 203-glioma target cells gradually increased following the regression of the tumors after irradiation. The maximum killer activity for 203-glioma target cells was observed 11 days after irradiation and natural killer activity also increased after irradiation. The killer activity for 203-glioma target cells decreased after treatment with anti-Thy 1.2 and complement. Therefore, killer T-cells may play an important role in this cell-mediated immunity. The relation between the regression of the tumors following radiotherapy and the increase of killer activity may indicate that the effects of radiotherapy are related to the immunological activity of the hosts in addition to the direct cell-killing effects of radiation. These results indicate that the immunological response of patients with brain tumors should be examined both during and after the course of radiotherapy.
