Emerging roles of neutrophils in immune homeostasis

Neutrophils, the most abundant innate immune cells, play es-sential roles in the innate immune system. As key innate im-mune cells, neutrophils detect intrusion of pathogens and initiate immune cascades with their functions; swarming (arresting), cyto-kine production, degranulation, phagocytosis, and projection of neutrophil extracellular trap. Because of their short lifespan and consumption during immune response, neutrophils need to be generated consistently, and generation of newborn neutro-phils (granulopoiesis) should fulfill the environmental/systemic demands for training in cases of infection. Accumulating evidence suggests that neutrophils also play important roles in the regu-lation of adaptive immunity. Neutrophil-mediated immune re-sponses end with apoptosis of the cells, and proper phagocy-tosis of the apoptotic body (efferocytosis) is crucial for initial and post resolution by producing tolerogenic innate/adaptive immune cells. However, inflammatory cues can impair these cascades, resulting in systemic immune activation; necrotic/py-roptotic neutrophil bodies can aggravate the excessive inflam-mation, increasing 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 studies of neutrophil function as players of immune response.

Automated summary

Neutrophils, as the most abundant innate immune cells, play crucial roles in the immune response, including detecting pathogens, initiating immune cascades, and regulating adaptive immunity.