Impairment of antimicrobial defense following total body irradiation of mice.

Abstract

Abstract A standard subacute streptococcal infection spread more rapidly in C 57 black mice subjected to single total-body x-ray exposures in the LD 50 range than in nonirradiated controls. Cumulative mortality curves in the two groups were parallel but the average survival time was significantly reduced by irradiation. Using the average day of death as a criterion, impairment of resistance was apparent within twenty-four hours after irradiation at this dose level, increased to a maximum between three and seven days after irradiation, and gradually returned to normal by fifteen days after treatment. Penicillin in large doses started within twenty-four hours after infection was effective in eliminating deaths due to bacteremia in the irradiated mice, despite the presence of a profound leukopenia. Aureomycin was somewhat less effective at the dose levels studied. In a preliminary experiment, spleen shielding failed to protect C 57 black mice against the profound impairment of antimicrobial defenses caused by systemic irradiation. It has since been shown that this response may be genetically conditioned, in that spleen-shielding of mice of this strain confers relatively little protection against the lethal effect of radiation in contrast to the striking protection noted in other strains.