Effect of x-irradiation on immunocompetency of T-lymphocytes

Effect of x-irradiation on various aspects of cell-mediated immune reactions is studied. The irradiated splenic lymphocytes could transform to blast cells upon stimulation with PHA, but could not divide into small lymphocytes. It was concluded that irradiation at doses higher than 500 rads inhibits the differentiation of lymphocytes to effector cells upon stimulation with antigens. The irradiated immune lymphocytes were able to kill target tumor cells when the cytotoxicity was tested immediately after irradiation with doses as high as 500 rads. The cytotoxicity of immune lymphocytes diminished, however, 7--10 hours after irradiation. The splenic lymphocytes irradiated with doses as high as 200 rads could stimulate allogeneic lymphocytes 2 days after the irradiation. It thus appeared that irradiation cannot immediately abolish the antigenicity of lymphocytes to stimulate allogeneic lymphocytes. The combined effect of irradiation and T-cell-mediated immune reaction to reduce clonogenecity of target tumor cells in vitro is simple additive.