The Neutrophil Life Cycle

Neutrophils are produced by committed progenitors in the bone marrow and some extramedullary tissues. The lifetime of mammalian neutrophils remains controversial. Neutrophils are found in most healthy tissues at varying numbers. Manipulation of the neutrophil life-cycle may be a promising strategy for the treatment of inflammatory diseases. Differences among species may reflect the remarkable sensitivity of neutrophils to environmental conditions. Neutrophils are recognized as an essential part of the innate immune response, but an active debate still exists regarding the life cycle of these cells. Neutrophils first differentiate in the bone marrow through progenitor intermediaries before entering the blood, in a process that gauges the extramedullary pool size. Once believed to be directly eliminated in the marrow, liver, and spleen, neutrophils, after circulating for less than 1 day, are now known to redistribute into multiple tissues with poorly understood kinetics. In this review, we provide an update on the dynamic distribution of neutrophils across tissues in health and disease, and emphasize differences between humans and model organisms. We further highlight issues to be addressed to exploit the unique features of neutrophils in the clinic. Neutrophils are recognized as an essential part of the innate immune response, but an active debate still exists regarding the life cycle of these cells. Neutrophils first differentiate in the bone marrow through progenitor intermediaries before entering the blood, in a process that gauges the extramedullary pool size. Once believed to be directly eliminated in the marrow, liver, and spleen, neutrophils, after circulating for less than 1 day, are now known to redistribute into multiple tissues with poorly understood kinetics. In this review, we provide an update on the dynamic distribution of neutrophils across tissues in health and disease, and emphasize differences between humans and model organisms. We further highlight issues to be addressed to exploit the unique features of neutrophils in the clinic. caused by deficiency in a gene required for lysosomal trafficking and phagocytosis that results in immune deficiency and albinism. immunodeficiency characterized by mutations in genes needed for the generation of ROS in granulocytes. type of hematopoietic progenitors that give rise to all myeloid-lineage cells in adult hematopoiesis. comprises a period of systemic immune suppression induced by extensive tissue damage or uncontrolled infection. SIRS and CARS can coexist. a model of granulopoiesis in which immature, but not proliferative, neutrophils give rise to a progressively mature neutrophils. technique combining mass spectrometry and flow cytometry to allow multiparametric (>30) assessment of cell markers. a preparation of cells that have been centrifuged on a slide for staining and morphological evaluation. two receptors (E- and P-selectins) present on endothelial cells that enable leukocyte rolling under flow conditions. group of enzymes and antimicrobial proteins found within cytoplasmic granules. process of proliferation and differentiation of granulocyte progenitors into mature cells. rare population of hematopoietic cells giving rise to all blood lineages. group of leukocytes found within the liver microvasculature. type of cell migration on endothelial surfaces and within blood vessels. macrophages of the liver. subset of neutrophil progenitors that rarely divide in the steady-state but activate upon acute demand for granulopoiesis. process of mobilization of immature neutrophils in peripheral blood. group of genetic disorders that affect the capacity of leukocytes to roll or adhere on the vascular endothelium. regions (e.g., of the spleen) at the interface between the lymphoid white pulp and the nonlymphoid, macrophage-rich red pulp. population of intravascular neutrophils adhered to the endothelial lining; not free-flowing in the bloodstream. released by activated neutrophils; DNA-based structures harboring microbicidal and prothrombotic properties. subset of neutrophils with T cell-suppressive activity. group of hematopoietic cells already committed to the neutrophil lineage by successive proliferation and/or differentiation. the appearance of immature forms of neutrophils in the blood after release into the bloodstream. theoretical phenomenon whereby neutrophils change their phenotype and function. experimental system that allows the study of shared exchange of circulatory molecules or cells between organisms, and normally achieved by surgical conjoining of circulatory systems. intermediate activation state of neutrophils that involves active intracellular signaling. approach typically based on metabolic labeling of cells to follow their dynamics (e.g., in live animals). ratio of blood neutrophils to mitotic precursors in the bone marrow. population of neutrophils in the bone marrow rapidly mobilized into the circulation during stress conditions. neutrophils that lack the glycoprotein ligands to engage selectins during the rolling process. syndrome characterized by enhanced systemic inflammatory signals caused by extensive tissue damage or uncontrolled infections. labeling method to detect early apoptosis in cells that undergo extensive DNA degradation.