The final step in programmed cell death: phagocytes carry apoptotic cells to the grave.

As cells undergo apoptosis, they are recognized and removed from the body by phagocytes. This oft-overlooked yet critical final step in the cell-death programme protects tissues from exposure to the toxic contents of dying cells and also serves to prevent further tissue damage by stimulating production of anti-inflammatory cytokines and chemokines. The clearance of apoptotic-cell corpses occurs throughout the lifespan of multicellular organisms and is important for normal development during embryogenesis, the maintenance of normal tissue integrity and function, and the resolution of inflammation. Many of the signal-transduction molecules implicated in the phagocytosis of apoptotic cells appear to have a high degree of evolutionary conservation, and therefore the engulfment of apoptotic cells is likely to represent one of the most primitive forms of phagocytosis. With the realization that the signals that govern apoptotic-cell removal also serve to attenuate inflammation and the immune response, as well as initiate signals for tissue repair and remodelling in response to cell death, the study of apoptotic cell clearance is a field experiencing a dynamic increase in interest and momentum.