The serine proteases released by activated polymorphonuclear neutrophils (NSPs) contribute to a variety of inflammatory lung diseases, including cystic fibrosis (CF). They are therefore key targets for the development of efficient inhibitors. Although rodent models have contributed to our understanding of several diseases, we have previously shown that they are not appropriate for testing anti-NSP therapeutic strategies (Kalupov, Brillard-Bourdet, Dade, Serrano, Wartelle, Guyot, Juliano, Moreau, Belaaouaj, Gauthier 2009, J Biol Chem, 284,34084-34091). Thus, NSPs must be characterized in an animal model that is much more likely to predict how therapies will act in humans in order to develop protease inhibitors as drugs. The recently developed CFTR-/- pig model is a promising alternative to the mouse model of CF (Rogers, Stoltz, Meyerholz, Ostedgaard, Rokhlina, Taft, Rogan, Pezzulo, Karp, Itani, et al. 2008, Science; 321(5897):1837-1841). We have isolated blood neutrophils from healthy pigs and determined their responses to the bacterial pathogens Pseudomonas aeruginosa and Staphylococcus aureus, and the biochemical properties of their NSPs. We used confocal microscopy and antibodies directed against their human homologues to show that the three NSPs (elastase, protease 3 and cathepsin G) are enzymatically active and present on the surface of triggered neutrophils and neutrophil extracellular traps (NETs). All the porcine NSPs are effectively inhibited by human NSP inhibitors. We conclude that there is a close functional resemblance between porcine and human NSPs. The pig is therefore a suitable animal model for testing new NSP inhibitors as anti-inflammatory agents in neutrophil-associated diseases such as CF.