Clearance of apoptotic cells by phagocytes

Abstract

Apoptosis or programmed cell death is a physiologic process used to eliminate unwanted or damaged cells. This processoccurs in many tissues during normal and pathologic processes throughout life. Cells undergoing apoptosis are rapidlyremoved from the body by both professional and non-professional phagocytes without neutrophil recruitment and inflammation.This phagocytic clearance or efferocytosis of the apoptotic cells is a multi-step process involving diverse interactionsbetween a wide variety of receptors on phagocytes and ligands expressed on or secreted from apoptotic cells. The dyingcells secrete unique signals called “find-me” signals which attract phagocytes to the site of apoptotic cell death. In theabsence of “don’t eat-me” signals, apoptotic cells are selectively recognized and phagocytosed through “eat-me” signalsexpressed on apoptotic cell surface. Efficient apoptotic cell removal prevents secondary necrosis of dying cells, which canrelease intracellular contents and cause inflammation. In addition, the release of anti-inflammatory mediators from phagocytesis necessary for silencing the immune response. Thus, the defective of apoptotic cell clearance has been linked to pathologicinflammation found in many chronic inflammatory diseases such as autoimmune diseases and atherosclerosis.

Key words: Efferocytosis, Apoptosis, “Find-me” signals, “Eat-me” signals, “Don’t eat me” signals