The Immunologic Status of the Host and Pyelonephritis: A Study of Retrograde Escherichia Coli Urinary Infection in Rats

Summary and Conclusion Retrograde infection of the urinary tract with a strain of Escherichia coli O22 K-negative was given to prevaccinated and to nonvaccinated rats. Rats with healed prior infection were rechallenged. Repeated retrograde infusions were given some animals to provide antigen in the renal pelvis in order to test the hypothesis that “sterile” inflammation observed in pyelonephritis might be caused by an antigen-antibody reaction; also, repeated infection stressed the protection afforded by serum antibody against the development of pyelonephritis. Renal lesions were caused by bacterial growth in the kidney pelvis and medulla. Serum antibody always tended to be protective as shown by the presence of fewer positive cultures from the kidney and less frequent and less severe gross and microscopic lesions. A decrease in the serum antibody titer was regularly observed 4 to 8 months after vaccination. Infection and bacterial lesions in the kidney increased during this time. Rats with healed prior infection but no circulating antibody were just as susceptible as control animals to an initial rechallenge, but were protected relative to controls if repeated challenges were given. Serum antibody did not prevent retrograde infection of the medulla, especially with repeated challenges, and did not cure established medullary infection. Late lesions were poorly correlated with the serum antibody titer. No adverse effect from anti-bacterial antibody was shown.