The Effect of Cobalt-60 Gamma Radiation on Tetanus Antitoxin Formation in Mice

Abstract

Summary Cobalt-60 γ whole body irradiation markedly depresses tetanus antitoxin in mice when given 6 hr, 1 day, 7 days, 14 days, and 21 days before a primary injection of fluid tetanus toxoid. The animals irradiated 14 and 21 days before the primary stimulus recovered sufficiently from radiation to react to the primary injection, since they later produced considerable amounts of antitoxin when given a secondary antigenic stimulus. The inhibitory effect of 650 rep γ radiation on the primary antibody response was as effective when alum precipitated toxoid was used for the primary stimulus. A radiation dose of 350 rep given 1 hr before the secondary stimulus had little effect on depressing antitoxin formation. γ Radiation doses of 450 to 750 rep effectively inhibited the secondary antitoxin response. The depressing effect was more marked with increased amounts of radiation. γ Radiation of 650 rep severely inhibited the secondary antitoxin response when radiation was given 6 hr to 30 min before the secondary antigenic stimulus. A total dose of 1,000 rep given in 4 doses of 250 rep at 5-day intervals depressed the secondary response by only 40%. When 650 rep whole body radiation was given in a single exposure the depressing effect on antitoxin formation was much greater than when the radiation was given in 10, 5, 3, or 2 divided doses. When radiation exposure was given at the peak of the antitoxin level (10th day after the secondary stimulus) and the mice were bled 10 days later, the antitoxin level was slightly reduced. There was no appreciable effect on the antitoxin level when mice were given 650 rep 21 days after the secondary stimulus and bled 5 days later. If the radiation was given 21 days after the second injection and the animals were bled 10 and 21 days later, the depressing effect was more pronounced than when radiation was given 10 days after the second injection. The depressing effect on the antitoxin level was greater when serum was obtained 21 days after exposure to radiation than on the 10th day post-radiation.