Effects of X-Irradiation on Susceptibility to Infection Following Oral Challenge in Immunized and Nonimmunized Mice

Summary Immunization with Salmonella typhimurium or Bacterium tularense, prior to near LD50 radiation, statistically increased resistance to oral challenge with the homologous living organism when the immunizing procedure conferred a sufficiently high degree of immunity. Antibiotic therapy in conjunction with preradiation immunization was more effective in increasing resistance than either of these methods used alone. A large total dose (900 r) given in regular small increments was found to be far less detrimental to the host defenses of the mouse than single exposure to smaller lethal doses.