Early apoptotic Jurkat T cells undergo capping of CD43, and its polylactosaminyl saccharide chains serve as ligands for phagocytosis by macrophages. This suggests the presence of a polylactosaminoglycan-binding receptor on macrophages. Here we show that this receptor is nucleolin, a multifunctional shuttling protein present in nucleus, cytoplasm, and on the surface of some types of cells. Nucleolin was detected at the surface of macrophages, and antinucleolin antibody inhibited the binding of the early apoptotic cells to macrophages. Nucleolin-transfected HEK293 cells expressed nucleolin on the cell surface and bound the early apoptotic cells but not phosphatidylserine-exposing late apoptotic cells. This binding was inhibited by anti-nucleolin antibody, by polylactosamine-containing oligosaccharides, and by anti-CD43 antibody. Deletion of the antibody binding region of nucleolin resulted in loss of the apoptotic cell-binding ability. Moreover, truncated recombinant nucleolin in solution containing this region blocked the apoptotic cell binding to macrophages, and the blocking effect was cancelled by the oligosaccharides. These results indicate that nucleolin is a macrophage receptor for apoptotic cells.Macrophages and other phagocytes recognize and ingest apoptotic cells in tissue, preventing their lysis and subsequent release of harmful or immunogenic intracellular components. Therefore, clearance of apoptotic cells by phagocytes is crucial in the maintenance of tissue turnover and homeostasis. Moreover, it has been suggested that the apoptotic cell-ingested phagocytes play a role in suppression or resolution of inflammation (1-5).Cells undergoing apoptosis display a variety of "eat me" signals, namely cell-surface changes to be recognized by phagocytes. These include externalization of phosphatidylserine (PS),3 as yet little identified alterations of carbohydrates, and unidentified alterations of other membrane components such as intercellular adhesion molecule-3 and "thrombospondin binding sites" (1-5). Among these, the most common and the best-characterized change is externalization of PS, although the mechanism of externalization has not been fully understood (6, 7).In contrast to the poor understanding of the nature of eat me signals, various proteins of phagocyte membrane or in extracellular fluid have been reported as receptors or bridging factors for apoptotic cells. For externalized PS on apoptotic cells, CD36 (8), CD68 (9), CLA-1 (10), LOX-1 (11), and PS receptor (12) have been reported as phagocyte receptors; a serum protein  2 -glycoprotein I (13), complement component C3bi (14), and milk fat globule-epidermal growth factor-factor 8 (15) have been reported to bridge apoptotic cells and phagocytes through exposed PS. For intercellular adhesion molecule-3 on apoptotic cells, CD14 was suggested to be a macrophage receptor (16). Thrombospondin is also known as a bridging protein between unidentified sites on apoptotic cells and CD36 or vitronectin receptor (␣ v  3 integrin) on phagocytes (17). In addi...