Tethering of Apoptotic Cells to Phagocytes through Binding of CD47 to Src Homology 2 Domain-Bearing Protein Tyrosine Phosphatase Substrate-1

• DOI: 10.4049/jimmunol.171.11.5718
• Publication Date: 2014-04-21T01:32:01Z
• Authors: Kazutoshi Tada; Masato Tanaka; Rikinari Hanayama; Keiko Miwa; Azusa Shinohara; Akihiro Iwamatsu; Shigekazu Nagata
• Keywords: 0301 basic medicine; Membrane Glycoproteins; Macrophages; Antibodies, Monoclonal; Apoptosis; CD47 Antigen; Mice, Transgenic; Neural Cell Adhesion Molecule L1; Antigens, Differentiation; Cell Line; Mice, Inbred C57BL; Mice; 03 medical and health sciences; Cricetulus; Antigens, CD; Cell Line, Tumor; Cricetinae; NIH 3T3 Cells; Animals; Humans; Female; Carrier Proteins

Abstract Apoptotic cells are swiftly phagocytosed by macrophages and immature dendritic cells. In this study, we found that one mouse macrophage cell line (BAM3) engulfed apoptotic thymocytes, but not a lymphoma cell line (WR19L). mAbs that inhibited the phagocytosis of apoptotic thymocytes by BAM3 were identified. Purification of the Ag revealed that it was Src homology 2 domain-bearing protein tyrosine phosphatase substrate-1 (SHPS-1). CD47, the ligand for SHPS-1, was expressed in mouse thymocytes, but not in WR19L. When WR19L was transformed with CD47, the transformants, after induction of apoptosis, could be phagocytosed by BAM3. The WR19L transformants expressing CD47 were more efficiently engulfed in vivo by splenic dendritic cells than the parental WR19L. Masking of the phosphatidylserine exposed on apoptotic thymocytes inhibited the engulfment, whereas the anti-SHPS-1 mAb inhibited not only the engulfment, but also the binding of apoptotic cells to phagocytes. These results indicate that macrophages require CD47 and phosphatidylserine on apoptotic cells for engulfment, and suggest that the interaction between CD47 and SHPS-1 works as a tethering step in the phagocytosis.