The Susceptibility of Irradiated Mice to Infection as a Function of Post-Irradiation Time

Abstract

Summary The susceptibility of mice to airborne Streptococcus zooepidemicus was determined over a 50-day period following 350 r whole body X-irradiation. Bacterial LD50 values were determined for normal and irradiated mice on 12 different post-irradiation days during this period, and the changes in susceptibility in each case expressed as the ratio of the two. The resulting curve relating susceptibility to post-irradiation time indicated a linear increase in susceptibility over the first 15 days, reaching a peak five times that of controls, followed by an exponential drop approaching the control level shortly after 30 days. The possible relationship of this phenomenon to other radiation effects is discussed. Mice subjected to sublethal doses of radiation exhibit a time pattern of change in susceptibility to infection which is different from the time pattern reported for various post-irradiation changes. Previous immunological studies following irradiation have not been sufficiently quantitative to permit interpretations or correlations with the results herein reported.