Caspase-1 activity (a), IL-18 protein (b), neutrophil infiltration (c), and active form of IL-18 (d) in the kidney in neutrophil-depleted mice with ischemic ARF. (a) Caspase-1 activity increased in both vehicle-treated (neutro⁺) and neutrophil-depleted (neutro^–) mice with ARF. *P < 0.001 vs. sham; **P < 0.001 vs. sham, NS vs. neutro⁺; n = 5. (b) IL-18 protein was measured by the ECL assay that detects both pro–IL-18 and active IL-18. IL-18 was increased in ischemic ARF in neutro⁺ as well as neutro^– mice with ischemic ARF compared with sham-operated controls. IL-18 was higher in neutro⁺ mice than in neutro^– mice. *P < 0.001 vs. sham; **P < 0.01 vs. sham, P < 0.01 vs. neutro⁺; n = 11. (c) Neutrophil infiltration (neutrophils/mm²) was increased in ischemic ARF in neutro⁺ and prevented in neutro^– mice with ischemic ARF. *P < 0.01 vs. sham; **P < 0.01 vs. vehicle-treated ARF, NS vs. sham; n = 7. (d) There was no difference in the amount of active IL-18 protein (18 kDa) on immunoblot analysis in whole-kidney homogenates in neutro⁺ versus neutro^– mice with ischemic ARF. Recombinant murine IL-18 (PeproTech Inc., Rocky Hill, New Jersey, USA) was used as a positive control (Pos). A representative picture of three separate experiments is shown.