In Vivo Imaging of Neutrophil Extracellular Traps (NETs): Visualization Methods and Outcomes

Abstract

Neutrophils comprise the first line of innate immune defense during a host-pathogen interaction. They attack microorganisms directly through three different methods, of which, phagocytosis and degranulation have been known and well-studied for decades. The formation of neutrophil extracellular traps (NETs) is the third and unique method, which was unveiled in 2004. Since then, many studies on NETs have been carried out. However, only few have successfully demonstrated the activity of NETs in vivo. Results of the in vivo studies on NETs have strengthened our understanding of their role in different situations. This review highlights the main in vivo studies, which have contributed in extending our understanding of the role of NETs during infections and diseases, thus indicating their advantages and limitations.

Figure 1

Mechanisms of NET formation. Upon activation, phenomenal morphological changes are observed during suicidal NETosis, which is followed by cell rupture and subsequent cell death. Contrarily, in vital NETosis, NETs are released rapidly by the active and functional NET-releasing neutrophils through blebbing of the nuclear envelope and vesicular exportation.