Apoptotic cells express phosphatidylserine on the outer leaflet of the plasma membrane, which delivers an 'eat me' signal to phagocytes. In the Journal of Experimental Medicine, Nakahashi-Oda et al. show that CD300a, a transmembrane protein expressed by myeloid cells, binds phosphatidylserine on apoptotic cells but does not mediate phagocytosis by macrophages. Instead, after binding to phosphatidylserine, CD300a recruits the phosphatase SHP-1 and delivers an inhibitory signal, which results in suppression of the expression of cytokines and chemokines such as TNF, IL-13 and CCL2 in mast cells and macrophages. In a mouse model of peritonitis, enhanced chemokine secretion from CD300a-deficient mast cells results in heightened recruitment of neutrophils to the peritoneal cavity and more-efficient bacterial clearance. These results indicate that apoptotic cells suppress inflammatory responses by mast cells and macrophages to help prevent excessive inflammation during bacterial infection.

J. Exp. Med. 209, 149–1503 (2012)