Active cells choose life

When macrophages perform their search-and-destroy missions, it is not simply up to apoptotic cells to flag down their destroyers. New results from Simon Brown (University of Edinburgh, Edinburgh, UK) and colleagues reveal that viable cells must actively avoid engulfment by phagocytes. A single cell adhesion molecule, CD31, can lead to either engulfment or escape.Brown and his colleagues found CD31 by purifying proteins involved in tethering of cells to macrophages at low temperatures, when phagocytosis and cytoskeletal rearrangements were inhibited. Both viable and apoptotic leukocytes bound to macrophages through homophilic CD31 interactions. At 37°C, however, this interaction was transient for viable leukocytes. The cytoplasmic portion of CD31 imparted these cells with the ability to avoid destruction by actively promoting detachment from the macrophages. Apopotic cells had somehow lost this capability.

“‘Eat-me signals’...