Abstract

Neutrophils are essential phagocytes of the innate immune system. They engage pathogens via degranulation, phagocytosis and the release of extracellular web-like structures called neutrophil extracellular traps (NETs). Recent findings highlight novel immunomodulatory roles for these cells, particularly in the regulation of inflammation. Under sterile conditions, NET release promotes inflammation and atherosclerosis by turning on pro-inflammatory cytokine expression in lesion-associated macrophages. Moreover, during infection neutrophils regulate their own recruitment conditionally by adjusting their cytokine expression according to the size of the microbes they encounter. The differential localization of reactive oxygen species (ROS) generated in response to microbes of different size plays a critical role in regulating interleukin-1β expression and the formation of neutrophil clusters required to clear large microbes. Finally, neutrophil derived ROS can regulate function of other cells such as T cells and suppress tumour growth.