NEUTROPHIL EXTRACELLUR TRAPS (NET) - NEW NEUTROPHIL STRATEGY TO COMBAT PATHOGENS

Neutrophils are one of the main types of effector cell engaged in the innate immune response and comprise first line of defense against pathogens. At the inflammatory site the cells eliminate pathogens and then die by apoptosis. It was commonly recognized that neutrophils utilize two ways to fight pathogens: phagocytosis and degranulation. However, in 2004 it was discovered that neutrophils can also eliminate infectious agents by formation of Neutrophil Extracellular Traps (NET) that capture and kill microorganisms. They are composed of decondensated chromatin to which specific proteins from the neutrophilic granules are attached. NETS are extracelularly released where they immobilize pathogens and secure their contact with antibacterial molecules. To date only some mechanisms of NET formation are described but it is decisively established that reactive oxygen species formed by the NADPH oxidase pathway are critical for this process. It was also reported that the release of NETs might be directly induced by pathogens or indirectly by platelets that firstly interact with microbes and subsequently with neutrophils. Altogether the published data suggest that NETs are important for pathogen elimination, however, their excessive production and/or removal might lead to abnormalities and development of severe diseases.