Clearance of apoptotic cells: getting rid of the corpses

The efficient elimination of apoptotic cells is crucial for tissue homeostasis in multicellular organisms. Secreted "find-me," exposed "eat-me," and lacking "don't-eat-me" signals comprise the central elements of apoptotic cell removal, thus preventing the release of intracellular contents into the surrounding tissue. This is of special importance, as there is growing evidence that the onset of autoimmune disorders can be linked to the inefficient removal of apoptotic cells. This review focuses on the signals displayed by apoptotic cells, the bridging and receptor molecules on the phagocyte, and is intended to present a simplified model of the phagocytic synapse. Additionally, the recent discovery of lysophosphatidylcholine functioning as soluble attraction signal is discussed in the general context of apoptotic cell clearance.