Beginnings of a good apoptotic meal: the find-me and eat-me signaling pathways.

Prompt and efficient clearance of apoptotic cells is necessary to prevent secondary necrosis of dying cells and to avoid immune responses to autoantigens. Recent studies have shed light on how apoptotic cells through soluble "find-me" signals advertise their presence to phagocytes at the earliest stages of cell death. Phagocytes sense the find-me signal gradient, and in turn the presence of dying cells, and migrate to their vicinity. The apoptotic cells also expose specific "eat-me" signals on their surface that are recognized by phagocytes through specific engulfment receptors. This review covers the recent progress in the areas of find-me and eat-me signals and how these relate to prompt and immunologically silent clearance of apoptotic cells.