Results: Impairment of leukocyte recruitment (FTVII/−) and neutrophil depletion resulted in more than a 50% reduction in NSAID-induced injury. However, mice deficient in mature T and B cells had NSAID-induced damage comparable to control mice. Leukocyte activation was required for NSAID-induced damage because the gp91phox−/− mice were less susceptible to NSAID injury than wild-type mice.