Neutrophils are the first line of defense of the immune system against infection. Among their weaponry, they have the ability to mix and extrude their DNA and bactericidal molecules creating NET-like structures in a unique type of cell death called NETosis. This process is important in order to control extracellular infections limiting collateral damage. Its aberrant function has been implicated in several human diseases including sepsis and autoimmune disease. The purpose of the present paper is to give a general introduction to this concept. 1. (N)ETosis Polisegmented granular cells are the immune system’s first line of defense against infections. They have been considered short-lived cells with unspecific functions of phagocytosis, granular secretion, and the production of reactive oxygen species (ROS) [1]. This knowledge has been challenged by several lines of evidence, including the formation of extracellular traps (ET), a defense mechanism consisting of the extrusion of intracellular material in the form of neutrophils extracellular traps (NETs) to the surrounding extracellular medium in order to concentrate antibacterial substances and snare invading microorganisms; such a process is often accompanied by cell death. The purpose of the present paper is to give a general introduction to this concept. 2. The Neutrophil Human neutrophils constitute the first line of defense of innate cellular immunity. As the most abundant subtype of leucocytes in peripheral blood, they constitute approximately 70% of these cells [2, 3]. They are terminally differentiated cells with a life span of 12 to 15 hours [4], whom after this time period undergo apoptosis: this life span can be extended after exposition to several substances like cytokines [5]. Under light microscopy, these cells have an approximate diameter of 12 to 15？μm and a nucleus with several lobules [2]. They also have a cytoplasm rich in different granules plenty of antimicrobial peptides [3] and enzymes necessary to synthesize several substances, including arachidonic acid derivates with either inflammatory properties like tromboxans and leucotriens [6], or negative regulators of inflammation such as prostaglandins, lipoxins, protectins, and so forth. These substances can be produced entirely within the neutrophils [6] or in conjunction with other cells using transcellular pathways to produce lipoxins [7]. Neutrophils can produce chemokines, cytokines from the tumor necrosis factor (TNF) superfamily, angiogenic and fibrogenic factors, and pattern recognition molecules such as pentraxins, collectins,
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