Transient Increase in Resistance of Mice to Experimental Infection Following a Small Dose of X-Radiation. ∗

Abstract

Summary

CF-1 female mice, 9-10 weeks old, were exposed to a small dose of whole body X-radiation (50, 75, or 100 r) and together with unirradiated controls were challenged at various intervals by intraperitoneal injection of graded inocula of Pseudomonas aeruginosa. Comparison of the LD₅₀'s (30 days) of irradiated and control mice in each challenge showed a small but significant increase in resistance to the experimental infection during the 4th week following irradiation with 75 or 100 r. Exposure to 75 r was more effective than 100 r. The results suggest a possible explanation of “acquired radio-resistance.”