The above information makes a strong case for PMNs playing a significant role in ALI. However, it is interesting to note that ARDS has been described as developing in patients with neutropenia (98) (99) (100) . In addition, following G-CSF therapy in pneumonia and sepsis patients, the incidence of ARDS was not increased (93, 101) and, during experimental ALI or pneumonia, PMNs have been shown to migrate to the lungs without exerting deleterious effects (102, 103) . Thus, other mechanisms also are likely to be involved in the pathogenesis of ALI.