Proteolytic enzymes also are a part of the PMN pathogen-clearing arsenal. While neutrophil elastase, cathepsin G, and metalloproteinases all have important roles in clearing invading pathogens and function in aspects of tissue remodeling/wound healing, they also are able to mediate neutrophil-induced tissue damage and can degrade extracellular matrix efficiently. Thus, while inhibition of neutrophil elastase improved respiratory function during septic ALI (74), its deficiency also rendered mice more susceptible to gram negative, but not gram positive sepsis (75) . In addition, deficiency of elastase and/or cathepsin G was accompanied by increased susceptibility to fungal infections, but decreased susceptibility to endotoxin-mediated inflammatory ALI (76) . Activated gelatinase A correlated with protein accumulation in the epithelial lining fluid in ARDS patients and might, therefore, be a potential marker for ARDS (77) . The inhibition of matrix metalloproteinases and elastase prevented lung dysfunction and reduced septic ALI in pigs (78) . The detailed mechanisms by which PMN mediate ALI via the involvement of proteolytic enzymes are reviewed in detail elsewhere (79, 80) .