AUTHOR=Miralda Irina , Uriarte Silvia M. , McLeish Kenneth R. TITLE=Multiple Phenotypic Changes Define Neutrophil Priming JOURNAL=Frontiers in Cellular and Infection Microbiology VOLUME=Volume 7 - 2017 YEAR=2017 URL=https://www.frontiersin.org/journals/cellular-and-infection-microbiology/articles/10.3389/fcimb.2017.00217 DOI=10.3389/fcimb.2017.00217 ISSN=2235-2988 ABSTRACT=Exposure to pro-inflammatory cytokines, chemokines, mitochondrial contents, and bacterial and viral products induces neutrophils to transition from a basal state into a primed one, which is currently defined as an enhanced response to activating stimuli. Although typically associated with enhanced generation of reactive oxygen species by the NADPH oxidase, neutrophils are activated by priming agents to undergo an array of phenotypic changes involving most neutrophil functions, in addition to enhanced responsiveness to activating signals. This review summarizes the breadth of phenotypic changes associated with priming and reviews current knowledge of the molecular mechanisms behind those changes. We conclude that the current definition of priming is too restrictive. Priming represents activation of neutrophil functions that regulate both the adaptive and innate immune responses, rather than just an enhanced ability to release toxic chemicals that kill microbes.