Identification of neutrophil extracellular traps in the blood of patients with systemic inflammatory response syndrome.

Neutrophils are able to form 'neutrophil extracellular traps' (NETs), which they use to trap and kill pathogens such as bacteria and fungi at the foci of infection. This observational study investigated the presence of NETs in the blood from critically ill patients and healthy volunteers. Fluorescent triple-colour immunocytochemical analysis of blood smears collected from patients with systemic inflammatory response syndrome (SIRS; associated with various clinical conditions) who had been hospitalized in the intensive care unit, and healthy volunteers, was undertaken to identify NETs in the blood. Blood smears were stained for DNA, histone H1 and neutrophil elastase. NETs were identified in 10 of 21 (47.6%) blood samples from the study group compared with none of the blood samples from eight healthy volunteers. These data suggest that fluorescent triple-colour immunocytochemical staining of NETs in the blood could be used to simplify the early identification of critically ill patients with SIRS. Larger studies are required to clarify the pathophysiological role of NETs in this specific patient population.