Delayed hypersensitivity to Escherichia coli in the rat--a study of its possible relevance to the pathogenesis of kidney scars.

Rats sensitized to various strains of Escherichia coli (078, O2K13H1, O6K13H1 and O6K2a2cH1) showed cutaneous delayed type hypersensitivity (DTH) reactions after intradermal challenge with the same or a different strain of Esch. coli. Cutaneous DTH was transferred to non-sensitized rats by administration of lymphocytes from sensitized animals. The common antigen(s) responsible for DTH was not identified but DTH reactions were found to be unrelated to the O or K serotype of the Esch. coli strains used. Intrarenal administration of killed Esch. coli to animals showing cutaneous DTH and non-sensitized controls did not produce evidence of DTH reactions of the kidney. Instead it was shown that intrarenal administration of formalin- or heat-killed Esch. coli leads to kidney scarring in both sensitized animals and non-sensitized controls. These scars were comparable in severity, and were similar to those obtained after infection of the kidney with live organisms. It is concluded that DTH reactions do not play a role in the pathogenesis of kidney scarring associated with Esch. coli infection of the rat kidney but that the strains of Esch. coli studied possess a common heat- and formalin-stable nephrotoxic factor which induces kidney scarring.