Selective deficiency of thymus-derived lymphocytes in experimental pyelonephritis

The inflammatory response and tissue damage. The example of renal scars following acute renal infection

Most clinical and experimental evidence suggests that renal scarring occurs following urinary tract infections in those patients with an abnormality of the urinary tract or kidney function. Experimentally, bacterial multiplication within the kidney occurs only in the presence of obstruction, leading rapidly to acute exudative pyelonephritis and invariably to kidney scars within weeks. Various manipulations of the bacterial load and/or of the inflammatory response during acute pyelonephritis have demonstrated that the inflammatory processes, not the bacterial component of pyelonephritis, are responsible for permanent renal tissue damage. Polymorphonuclear leucocytes (PMNLs) infiltrating the kidney tissue during acute pyelonephritis appear to release metabolites that are toxic to the parenchyma. Indeed, both the prevention of PMNL influx into renal tissue, by means of colchicine or cyclophosphamide, and the inactivation of some of their toxic metabolites, by means of dapsone, have led to the prevention of tissue damage and kidney scars. However, the most potent protective activity was observed with early antibiotic treatment, which stopped bacterial multiplication and prevented the early influx of PMNLs, thus preventing tissue damage and scar formation. Similar observations have been made in children with acute pyelonephritic episodes, in whom early and aggressive antibiotic treatment prevented subsequent kidney scars, while delayed treatment did not.

Pyelonephritis: the role of cell-mediated immunity defined in a congenitally athymic rat

Thymus-derived lymphocytes (T-cells) have been shown to be present in the inflammatory infiltrate in renal infection but their role in host defense mechanisms has not been defined. Indirect evidence suggested that T-cells contributed to host protection but selective depletion of T-cells did not influence the course of pyelonephritis. In the present report, the characteristics of the athymic New Zealand nude rat (rnunz), which lacks T-lymphocytes, are detailed. This mutant was then used to assess the effect of an absence of T-cells on the bacteriological and histopathological features of pyelonephritis. No significant differences in the bacteriological course of the disease were found. Apart from fewer lymphocytes in the kidney lesions of nude rats and a slight, lag in the resolution of these lesions, no differences were observed in the histopathological course either. These observations, which have analyzed the quantitative relationship between cell-mediated immunity (CMI) and host resistance to renal infection, have shown that a gross reduction in CMI does not affect host resistance once bacteria have gained access to the kidney.

Immunology of pyelonephritis in the primate model. V. Effect of superoxide dismutase

Ascending acute pyelonephritis was produced in monkeys by infusion of bacteria through a ureteral catheter to the point of intrarenal reflux. This led to a significant inflammatory response with death of renal tubular cells in the area of the tubular granulocytes and bacteria. We gave superoxide dismutase, and found that the inflammatory response was decreased and fewer tubular cells were killed. Ultrastructural change was also decreased in tubular cells adjoining phagocytosing neutrophils. This suggests that renal damage following a bacterial infection may be due to the production and release of superoxide into the tubular lumen during phagocytosis. We believe that it is the initial event which may lead to the eventual loss of renal tissue and function called chronic pyelonephritis.

Prevention of chronic experimental pyelonephritis by suppression of acute suppuration

In order to evaluate the importance of suppuration, persistent infection, and scar formation in the evolution of Escherichia coli chronic pyelonephritis, we treated rats with different antibiotic regimens at different stages of the disease. The results show that (a) if acute suppurative pyelonephritis is aborted with early antibiotic therapy, chronic pyelonephritis is prevented; (b) chronic pyelonephritis can develop even after eradication of infection if acute suppuration persists beyond 3 days; (c) persistent infection does not lead to chronic pyelonephritis, if the acute suppuration is suppressed; and (d) residual infection, antigen-load, antibody, and(or) cell-dependent autoimmune processes did not play a significant role. We interpret these results as evidence that the pathologic entity recognized as chronic pyelonephritis results from kidney damage, scarring and shrinkage secondary to acute suppuration.