Abstract

 

Neutrophils, the most abundant innate immune cells, play essential roles in innate immune system. As key innate immune cells, neutrophils surveil intrusion of pathogen and initiate immune cascades with their functions; swarming (arresting), cytokine production, degranulation, phagocytosis, and projection of neutrophil extracellular trap (NET). Due to their short lifespan and consumption during immune response, neutrophils should be generated persistently, and generation of newborn neutrophils (granulopoiesis) should fulfill the environmental/systemic demands for training in such a case of infection. Accumulating evidence suggests that neutrophils also play important roles in the regulation of adaptive immunity. Neutrophil-mediated immune responses end up with apoptosis of the cells, and proper phagocytosis of apoptotic body (efferocytosis) is crucial for initial and post resolution by inducing tolerogenic innate/adaptive immune cells. However, inflammatory cues can impair these cascades, which result in systemic immune activation; necrotic/pyroptotic neutrophil bodies can aggravate the excessive inflammation, enhancing inflammatory macrophage and dendritic cell activation and subsequent TH1/TH17 responses contributing to the regulation of the pathogenesis of autoimmune disease. In this review, we briefly introduce recent understandings of neutrophil function as players of immune response.