Polymorphonuclear (PMN) leukocytes from acute pyelonephritic exudates of rats were examined for cytoxicity against various target cells. Pyelonephritic PMN leukocytes caused lysis in vitro of syngeneic renal epithelial cells in 24 to 48 hr. They also caused lysis of allogeneic and xenogeneic target cells. The susceptibility to PMN-induced cytolysis was different among various target cell lines. Cell lysis proceeded at low ratios of effector to target cells and was not dependent on the addition of antibody or lectins. PMN isolated from peritoneal exudates (starch or endotoxin induced) were also cytoxic for the target cells. Cell-free supernatants from pyelonephritic PMN-target cell mixtures, or pyelonephritic PMN leukocytes cultured alone contained cytolytic substances which were nondialyzable and heat stable Finally, the urine of pyelonephritic rats was cytotoxic. These results suggest that PMN leukocytes and their cytotoxic mediators are directly involved in the pathogenesis of renal injury in pyelonephritis.

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This work was supported by United States Public Health Service Grants AI-12476 and AI-00391 and Grant 865-M from the Academic Senate of the University of California, San Diego.

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