Morphologic and immunohistologic study of pyelonephritis in rats by various bacteria and fungi. Special reference to inflammatory changes and localization of antigen.

Experimental pyelonephritis induced in rats by a single intrarenal injection of Pseudomonas aeruginosa, Serratia marcescens, Candida albicans, and Cryptococcus neoformans was studied pathologically and immunohistologically. The lesions which develop following intrarenal inoculation were similar to those seen during the course of pyelonephritis in man. Localization of the whole bacteria and the amorphous bacterial antigens and the whole fungi and the amorphous fungal antigens in the inflammatory lesions persisted up to 10-12 and 6-8 weeks, respectively. After that, continued inflammatory changes in progressive scarring can evolve in the absence of persistent bacterial or fungal antigens. Rat gamma globulin was localized in the plasma cells of the renal inflammatory infiltrates from 5-6 days to the end of the experiment (14th week). The incidence of progressive renal sclerosis was high in case of Candida pyelonephritis. The possible roles of progressive renal scarring by C. albicans are discussed.