Publisher Summary CD47 has a broad tissue distribution with expression on virtually all hematopoietic cells, including thymocytes, T cells, B cells, monocytes, platelets, and erythrocytes, as well as on epithelial cells, endothelial cells, fibroblasts, sperm, and tumor cell lines. CD47 is part of the Rh complex on erythrocytes and is not expressed on Rhnull erythrocytes. The CD47 structure is unusual in combining an IgSF domain with a multipass transmembrane mode of attachment to the cell membrane. CD47 is predicted to have five membrane-spanning regions, an N-terminal IgSF V-set domain and short cytoplasmic regions. Immunofluorescence microscopy has proved the C-terminal tail to be cytoplasmic. CD47 plays a role in the chemotactic and adhesive interactions of leucocytes with endothelial cells. The mechanism of action is not entirely understood, but is thought to involve the modulation of the function of integrins, with which CD47 is physically and functionally linked, and its binding to thrombospondin. CD47 mAbs also inhibit neutrophil migration across endothelium and epithelium, without affecting CD11b/CD18 integrin-mediated neutrophil adhesion to epithelium.