HEAT-STABLE ANTIGEN (MOUSE CD24) SUPPORTS MYELOID CELL-BINDING TO ENDOTHELIAL AND PLATELET P-SELECTIN

P-selectin is a Ca2+-dependent lectin that participates in leukocyte a dhesion to vascular endothelium and platelets. Myeloid cells and a sub set of T lymphocytes express carbohydrate ligands at the cell surface. Previously, we suggested that heat stable antigen (HSA/mouse CD24), a n extensively glycosylated cell surface molecule on many mouse cells, is a ligand for P-selectin. Here we show that HSA mediates the binding of monocytic cells and neutrophils to P-selectin. The monocytic cell lines ESb-MP and J774, peritoneal exudate cells, and bone marrow neutr ophils could bind to lipopolysaccharide-activated bend3 endothelioma c ells under rotation-induced shear forces and this binding was inhibite d by mAb to P-selectin and HSA. Blocking was weak at room temperature but more efficient at 4 degrees C when integrin-mediated binding was d ecreased. Also the adhesion of neutrophils to stimulated platelets exp ressing P-selectin was blocked by HSA- and P-selectin-specific mAb. La tex beads coated with purified HSA from myeloid cells bound to activat ed endothelioma cells or platelets, and the binding was similarly blac ked by mAb to P-selectin and HSA respectively. The HSA-coated beads we re stained with P-selectin-IgG, very weakly with L-selectin-IgG but no t with E-selectin-IgG. The staining was dependent on divalent cations and treatment with endoglycosidase F or neuraminidase indicated that s ialylated N-linked glycans were recognized. The presence of these glyc ans was confirmed by biosynthetic labeling studies. Our data suggest t hat HSA, in addition to the recently identified 160 kDa glycoprotein l igand on mouse neutrophils, belongs to a group of monospecific P-selec tin ligands on myeloid cells.