Effects of Active Immunization and of Total Body X-Irradiation upon the Humoral Bactericidal System of the Guinea Pig as Measured with Strains of Enteric Bacilli

摘要

1. 1. For a given strain of E. coli sensitive to serum, a characteristic number is killed when placed in intraperitoneal diffusion chambers in normal guinea pigs. A serum-resistant strain of E. coli multiplied within the chambers in a normal guinea pig whereas a serum-sensitive mutant strain derived from it was killed. Immunization of the guinea pigs did not result in significant increases in the number of bacteria killed within the diffusion chambers when a serumsensitive mutant or a naturally serum-sensitive strain were used as test organisms.2. 2. There was no evidence of a significant depression of complement-dependent humoral bactericidal activity after exposure of guinea pigs to total body x-irradiation (LD50). Contrary to some recent reports in the literature, no fall in the titer of naturally-occurring bactericidins for an E. coli and for an S. typhosa was found within 10 days after x-irradiation (LD50). Neither was there a decrease of bactericidal complement. A small and unexplained decrease in the ability of the guinea pig to kill E. coli in diffusion chambers was noted at 6 or 7 days after exposure to x-irradiation, but this was not associated with corresponding changes in the titer of bactericidal antibody or complement.3. 3. Infections in guinea pigs following total body x-irradiation (LD50) are predominantly due to Gram-positive organisms. This is in contrast to the mouse, in which it has been well established that a high percentage of postirradiation infections are due to Gram-negative enteric bacilli.