The Effect of Cobalt-60 Gamma Radiation on Passive Immunity *

A considerable amount of work has been reported in the literature on the effect of x-rays on antibody formation and immunity. With the exception of the reports from our laboratory,5"' the depressing effect of cobalt-60 gamma radiation upon immunity and antibody formation has not been reported. It would seem logical that x-rays and gamma rays should have a similar physiological effect. However, there is a greater difference between the wave length of the radioactive cobalt gamma ray and x-ray than there is between the antirachitic ultraviolet band and the ineffective band in the ultraviolet region. For this reason, we have chosen cobalt-60 gamma rays for our study of the effect of whole body ionizing radiation on the immunity mechanism in general. Because of the excellent review of the effect of x-rays on immunity by Taliaferro and Taliaferro,'l only references having a direct bearing on the experiments in this report will be included. Hollingsworth7 has reported that whole body irradiation has no effect on the rate of destruction of passively administered antibodies. This was true for both homologous and heterologous serum. Hale and Stoner' have also demonstrated that whole body gamma irradiation does not appreciably alter the disappearance of passively administered homologous tetanus antitoxin. Therefore, if sublethal whole body irradiation will depress the efficacy of such passively administered antibody, this procedure might be a means of studying the relationship of the cells of the passively immunized animal to the immunity produced by the antibody. Experiments were designed to test the effect of whole body irradiation on passive immunity to pneumococcus Type III. The radiation source was composed of twenty-one pieces of cobalt-60, arranged to give a uniform field at twelve inches from the source. Fifty mice could be irradiated at one time. The intensity at the time of these experiments was approximately 650 Rep. per hour and the LD50 for mice twenty-eight days of aget was 750 Rep. per hour.