Abstract

Extracellular traps (ETs) are webs of DNA, citrullinated histones, anti‐microbial peptides, and proteins that were not previously reported in Atlantic salmon (Salmo salar). ETs are mainly released from polymorphonuclear neutrophils (PMN) and are considered a novel PMN‐derived effector mechanism against different invasive pathogens. Here, we showed that Atlantic salmon‐derived PMN released ETs‐like structures in vitro in response to highly pathogenic facultative intracellular rickettsial bacteria Piscirickettsia salmonis. PMN were isolated from pre‐smolt Atlantic salmon and stimulated in vitro with oleic acid and P. salmonis. Extracellular DNA was measured using the PicoGreen™ dye, while immunofluorescence image analysis was used to confirm the classical components of salmonid‐extruded ETs. Future studies are required to better understand the role of Atlantic salmon‐derived ETs orchestrating innate/adaptive immunity and the knowledge on regulation pathways involved in this cell death process. Thus, comprehension of salmonid‐derived ETs against P. salmonis might represent novel alternative strategies to improve host innate defense mechanisms of farmed salmon against closely related rickettsial bacteria, as a complement to disease prevention and control strategies.