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.