Exacerbation of experimental pyelonephritis by cyclosporin A.

An athymic rat strain lacking functional T cells was used to assess the role of cell-mediated immunity (CMI) in host defence against renal infection. CMI was ruled out as a relevant host defence component, but when cyclosporin A (CsA) was administered to athymic animals, renal infection was exacerbated. CsA is thought to affect T lymphocyte function and, in the absence of a target cell, cellular defences in the athymic animal were not expected to be compromised by CsA. An effect on non-cellular defence mechanisms was therefore considered but our studies did not support this explanation--rather they indicated a depression of either cellular defences or of a specific cellular component. The present experiments have provided additional information on the relationship between CsA administration and the depression of host defence mechanisms but further studies will be necessary to identify the components affected.