Aging: A Temporal Dimension for Neutrophils

Neutrophils are first-responders, providing early protection against invading pathogens. Recent findings have revealed a temporal dimension to neutrophil function, associated with the clearance cycles for aging neutrophils, and also with a program that endows circulating neutrophils with distinct phenotypic and functional properties at different times of the day, before they are cleared from blood. We review here the process of neutrophil aging and its impact on homeostasis and inflammation. We outline the features of aged neutrophils, examine proposed mechanisms that drive aging, and discuss how these processes may contribute to tissue homeostasis and pathology. In this context we propose that neutrophil aging may optimize host defense by allowing neutrophils to anticipate infections while avoiding permanent activation and subsequent damage.