A marker for munching

When it comes to receptors for the phagocytosis of apoptotic cells, many have been proposed, but none has been proven. Now, Hoffmann et al. (page 649) report that a receptor for phosphatidylserine (PS) is uniquely required for engulfment of apoptotic cells, whereas a large number of other proposed receptors may function only in attachment of the apoptotic cell to the phagocytic cell. PS is exposed on the outer leaflet of cells when they become apoptotic, and thus it acts as a specific identifier of apoptotic cells. As for attachment to the phagocyte, it seems that pretty much anything will do.

Hoffmann et al. use a clever trick to get around the complexity of the surface of an apoptotic cell. Instead of apoptotic cells they use a novel target: red blood cells coated with...