Mendez, JonatanOstertagia ostertagi is a widespread parasite that causes significant production losses in the cattle industry. Recently discovered neutrophil extracellular traps (NETs) have been demonstrated as important effector mechanisms of neutrophils against various pathogens including parasitic worms. Exposure of neutrophils to O. ostertagi extract resulted in a significant release of extracellular DNA and co-localization of NET associated proteins histone and neutrophil elastase confirmed these structures of DNA as NETs. In response to both live and heat-killed O. ostertagi larvae, there was a similarly strong release of NETs. O. ostertagi induced NETs were significantly diminished by inhibition of enzymes NADPH oxidase, neutrophil elastase, and myeloperoxidase. Interestingly, NETs were also released in response to non-pathogenic nematode C. elegans indicating a potential conserved response to nematodes. Mouse neutrophils demonstrated a similar NET response to O. ostertagi however there was no response to C. elegans. Surprisingly, these NET responses did not appear to be dependent on production of reactive oxygen species (ROS) as has been previously reported. This is the first report indicating O. ostertagi-induced NET formation and indicates a potential role for NETs in the response against O. ostertagi infection.enThesisImmunology