PHYSIOLOGY OF RADIATION INJURY 1003 



been seen in the dog, but even in this species infection appears to be 

 related to mortality in animals surviving the first two weeks of irradiation 

 (Bennett, Rekers, and Howland, 1950). Total-body X irradiation of 

 guinea pigs has also been shown to result in a generalized tissue invasion 

 by cholera vibrio from the original focus of infection in the bowel (Bur- 

 rows et al., 1950a). The intensity of enteric infection appears to be 

 related to a decrease in coproantibody titer. It has been suggested by 

 Burrows and his associates (1950a) that a similar decrease in titer may 

 account for bacteremia in irradiated animals if natural immunity to 

 intestinal organisms is related to the coproantibody response. 



Mortality of irradiated animals may be reduced with suitable anti- 

 biotic therapy. Streptomycin and terramycin afford the most effective 

 protection to mice (Miller et al., 1950b; Hammond and Miller, 1950). 

 The incidence of diarrhea in rats is greatly diminished by terramycin or 

 aureomycin; survival may also be prolonged (Howland et al., 1950; 

 Furth, Coulter, and Howland, 1951). Mortality from internal radiation 

 (P 32 ) is decreased in this species when streptomycin and penicillin are 

 given in combination (Koletsky and Christie, 1950). Definite effects on 

 survival have not been observed in irradiated dogs with aureomycin 

 (Furth and Coulter, 1950; Allen et al, 1951). It is of interest that 

 prophylaxis with terramycin for 2 to 3 days prior to exposure reduces 

 radiation mortality in rats, presumably by altering the intestinal flora 

 and consequent bacteremia (Gustafson and Koletsky, 1951). In general, 

 antibiotic therapy leads to a reduction in the number of positive blood 

 cultures; pancytopenia is usually not altered, however, although gastro- 

 intestinal hemorrhage and ulceration may be diminished. 



Numerous reports of the effects of radiation on immunity have 

 appeared since the detailed observations by Hektoen in 1915 of altered 

 antibody formation following exposure to X rays. Decreased resistance 

 of irradiated animals to infection had actually been demonstrated some 

 years previously by Lawen (1909). Although there are some indications 

 of a protective or beneficial action with small dosages of radiation (Glenn, 

 1946), the evidence, for the most part, points to an impairment of 

 immunological responses and to an increased susceptibility to infection 

 as a result of irradiation. X irradiation decreases the Shwartzman 

 phenomenon of local tissue reactivity to intradermally injected bacterial 

 endotoxins (Becker, 1948) and also diminishes the renal lesions that occur 

 in rabbits after injection of bovine serum y- globulin (Schwab et al., 1950). 

 These effects may be related to suppression of antibody formation. The 

 extensive literature in this field has been the subject of recent reviews by 

 Taliaferro and Taliaferro (1951) and Craddock and Lawrence (1948). 



A marked reduction in the capacity to form antibodies has been demon- 

 strated when irradiation is accomplished shortly before or after immuniza- 

 tion (Hektoen, 1915; Murphy and Sturm, 1925; Craddock and Lawrence, 



