is the process by which phagocytic cells enter the tissues from capillaries
Phagocyte To reach the site of infection, phagocytes leave the bloodstream and enter the affected tissues. Signals from the infection cause the endothelial cells that line the blood vessels to make a protein called selectin, which neutrophils stick to on passing by. Other signals called vasodilators loosen the junctions connecting endothelial cells, allowing the phagocytes to pass through the wall. Chemotaxis is the process by which phagocytes follow the cytokine "scent" to the infected spot.[2] Neutrophils travel across epithelial cell-lined organs to sites of infection, and although this is an important component of fighting infection, the migration itself can result in disease-like symptoms.[64] During an infection, millions of neutrophils are recruited from the blood, but they die after a few days.[65]
Apoptosis The removal of dead cells by neighboring phagocytic cells has been termed efferocytosis.[62] Dying cells that undergo the final stages of apoptosis display phagocytotic molecules, such as phosphatidylserine, on their cell surface.[63] Phosphatidylserine is normally found on the inner leaflet surface of the plasma membrane, but is redistributed during apoptosis to the extracellular surface by a protein known as scramblase.[64] These molecules mark the cell for phagocytosis by cells possessing the appropriate receptors, such as macrophages.[65] The removal of dying cells by phagocytes occurs in an orderly manner without eliciting an inflammatory response.[66] During apoptosis cellular RNA and DNA are separated from each other and sorted to different apoptotic bodies; separation of RNA is initiated as nucleolar segregation.[67]