Effect of Immunity on Resistance to Infection in Irradiated Mice and Rats.

Abstract

Mice (N.I.H.) and rats (Sprague-Dawley) immunized with heat-killed Proteus prior to 475 r (LD5), withstood challenge with the living bacteria significantly better than their non-immunized, irradiated controls. Pre-radiation immunity to mixtures of the organisms commonly occurring in postmortem heart blood of irradiated mice (Proteus mirabilis, E. coli. alpha-streptococcus, Paracolon Pseudomonas) also conferred significant protection to mice challenged with similar mixtures of the living bacteria 5 days after 475 r. Pre-radiation immunization with such mixtures resulted in no significant improvement in survival rate in mice exposed to LD65-95 (625 r) doses of radiation nor was there any evidence of a shift in specific infection in the mice which died. Severe depletion of circulating granulocytes and possible impairment of phagocytic function may account for the lack of protection of the circulating antibody in the lethally irradiated mice.