CD44 REGULATES PHAGOCYTOSIS OF APOPTOTIC NEUTROPHIL GRANULOCYTES, BUTNOT APOPTOTIC LYMPHOCYTES, BY HUMAN MACROPHAGES

Phagocytosis of apoptotic neutrophil granulocytes by macrophages at in flammatory sites is an important determinant of the process by which i nflammation resolves. We demonstrate that phagocytosis of apoptotic ne utrophils, but not apoptotic lymphocytes, by human monocyte-derived ma crophages is augmented rapidly following ligation of CD44 by bivalent Abs in vitro. Previously defined inhibitors of apoptotic cell recognit ion did not affect CD44-augmented phagocytosis of apoptotic neutrophil s, suggesting that unique molecular recognition pathways are involved. These observations, together with the lack of effect of CD44 Abs upon macrophage phagocytosis of zymosan or Ig-opsonized erythrocytes, impl y that CD44 may regulate the differential clearance of apoptotic leuko cytes during evolution of inflammatory responses. This represents a no vel role for CP44 in inflammation and tissue repair.