William M. Hale

Effect of cobalt60 gamma radiation on susceptibility and immunity to trichinosis.

Summary 1. Cobalt60 gamma whole body irradiation of 550 to 650 (rep) increased the susceptibility of Swiss mice to infections with Trichinella spiralis. 2. Exposure of Trichinella-immune mice to 600 (rep) before administering a challenge infection destroyed their immunity to reinfection. 3. Data are presented on the effects of 680 (rep) radiation upon the total leukocyte count in the peripheral blood of mice. The sharp reduction in the number of circulating leukocytes may indicate that the role of cellular immunity should be emphasized more in acquired immunity to infections with Trichinella spiralis.

Effects of Ionizing Radiation on Immunity

The effect of radiation on the immune mechanism has been of academic interest for many years. Recently, the great increase in the number of personnel working with ionizing radiation, together with the development of nuclear weapons, has stimulated new interest in the study of radiation effect on immunity. An excellent discussion of the extensive literature concerning the effect of X-rays on immunity may be found in the review by Taliaferro and Taliaferro (1). Our present discussion will be limited to whole-body ionizing radiation effects on (1) resistance and acquired immunity to various organisms, (2) passive immunity, and (3) antibody formation. The material considered here has been selected primafily to give a representative cross section of the effect of whole-body ionizing radiation on immunity. Although a number of investigations on the susceptibility of the irradiated animal to viral infections has appeared in the literature (2-7), the first concerning radiation and immunity to viral infection was reported by Amoss et al. (8). They were able to increase the susceptibility of the monkey to poliomyelitis virus by large doses of X-rays but were unable to break the active immunity due to a previous infection.

The depressant effect of continuous cobalt-60 radiation on the secondary tetanus antitoxin response in mice.

The radiosensitivity of the secondary tetanus antitoxin response in mice was demonstrated after rather low doses of continuous gamma -radiation given at a dose rate of 4 rep/hr. Accumulated doses of 48 to 288 rep depressed antitoxin formation. Comparable doses of acute gamma radiation did not depress antitoxin production. Acute doses of 350 to 650 rep sharply depressed the secondary antibody response, however. Extended periods of continuous gamma -radiation from 10 to 28 days to accumulated doses of 960 to 2688 rep markedly depressed the secondary antibody response. An accumulated dose of 2688 rep was needed to depress antitoxin formation to the level observed after an acute dose of 650 rep. When the secondary stimulus of fluid tetanus toxoid was given prior to 10 days of continuous exposure to an accumulated dose of 860 rep, the secondary antibody respense was not depressed. Irradiated mice recovered the ability to produce a normal secondary antitoxin response during the second week after an accumulated dose of 1248 rep. The secondary antitoxin response was depressed in mice given long-continued gamma -radiation at a dose rate of 1 rep/hr. (auth)

Enhancing Effect of Continuous Cobalt-60 Gamma-Radiation on Susceptibility to Anaphylactic Shock in Mice'

Continuous exposure to gamma -radiation at a dose rate of 4 rep/hr enhanced the severity of anaphylactnic shock ln mice sensitized with tetanus toxoid and challenged 1 hour or 7 days postradiation with fluid tetanus toxoid. A sharp increase in susceptibility to fatal anaphylaxis was observed as the accumulated dose was increased from 192 to 288 rep. Recovery from the enhancing effect of continuous gamma -radiation began during the second week postradiation; complete recovery occurred during the third week after an accumulated dose of 672 rep. Anaphylactic shock was demonstrable in mice sensitized 6 months before challenge with the specific antigen. An enhanced susceptibility to fatal anaphylaxis was obtained when these animals were given an accumulated dose of 288 rep and challenged 1 hour postradiation. Passive anaphylaxis was more severe in irradiated mice sensitized with homopogous antitoxin 1 hour postradiation and challenged the following day with tetanus toxoid. The antihistaminic agent Thephorin afforded complete protection from fatal anaphypaxis in irradiated mice. (auth)