Neutrophil Recruitment

Neutrophils (polymorphonuclear cells or granulocytes) are terminally differentiated upon entering the blood from the bone marrow and are the most abundant type of immune cell in the circulation of humans and in the tissue during acute inflammation. Neutrophil recruitment from the blood into the underlying affected tissue is orchestrated, in part, by various families of adhesion molecules, chemokines, cytokines, and products of invading microorganisms. Neutrophils are a key source of local and systemic pro-inflammatory cytokines during acute inflammation. Neutrophils also generate chemotactic signals that attract monocytes and dendritic cells and influence their differentiation, and they secrete factors that drive T and B cell proliferation and differentiation. Neutrophils initiate the resolution of inflammation and play an important role in wound healing by instigating their own death (apoptosis) following pathogen engulfment (phagocytosis) and by promoting macrophage accumulation. These macrophage then dispose of the apoptotic neutrophils by phagocytosis.