Over recent years, neutrophil functions have extensively been reevaluted. For instance, it has been found that extracellular traps generated by activated neutrophils are able to perform a very effective antimicrobial activity against a plethora of microorganisms. In addition, neutrophils possess the ability to interact with monocytes/macrophages either via release of their granule content or via efferocytosis. Efferocytosis is based on neutrophil clearance by macrophages, which, in turn, exert pro- or antinflammatory effects. Furthermore, alarmins released by neutrophils have been shown to mobilize and activate dendritic cells as well as macrophages for antigenpresentation to occur. Finally, other researchers have demonstrated that neutrophils act as suppressor cells by deprivation of arginine in T cells. From a clinical point of view, it is well known that neutrophils are present as activated effector cells in a number of diseases such as infectious disease, sepsis, autoimmune disease, cardiovascular disease and tumors. They play pro-inflammatory and angiogenetic effects in some cases, while in other cases they depress host immune response. In this review, also emphasis will be placed on neutrophil functional deficits which seem to participate to the pathogenesis of various diseases, e.g., viral hepatitis C infection and inflammatory bowel disease. Finally, novel therapeutic measures able to modulate neutrophil functions will be described with special reference to both immune agents and natural products.
Keywords: Immune agents, innate immunity, natural products, neutrophils, phagocytosis, efferocytosis, macrophages, antinflammatory effects, arginine, angiogenetic effects
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