Biphasic Radiation-Sensitivity of The Transplantation Immunity for Rejection of An Allogeneic Ascites Tumor

Abstract

Transplantation immunity for second-set rejection of an allogeneic ascites tumor was induced by sensitizing mice with H-2-identical allogeneic spleen cells, and radiation-sensitivity of this immunity was studied. The immunity was not severely affected by 400 rads whole-body X-ray irradiation given at one day before the initial antigenic stimulation. In contrast, it was totally inactivated by 300-400 rads irradiation that was given one day before tumor challenge. An adoptive cell transfer experiment showed that alloreactive memory cells responsible for the immunity were unexpectedly highly radiosensitive. The immunity (memory), however, became resistant to 400 rads irradiation soon (one day) after challenge with the allogeneic tumor, and was resistant to 1500 rads for rejection of the tumor that was challenged at the second time when the initially challenged tumor was rejected. Corresponding to these observations, cells for allospecific CTL responses in peritoneal cavity of mice showed corresponding biphasic radiation-sensitivity.