A SIALOGLYCOPROTEIN FROM HUMAN-LEUKOCYTES FUNCTIONS AS A LIGAND FOR P-SELECTIN

P-selectin (CD62P), a Ca2+-dependent lectin expressed on activated pla telets and endothelial cells, functions as a receptor for myeloid and monocytoid cells. Previous reports have described a homodimeric sialog lycoprotein from human leukocytes and HL-60 cells specifically recogni zed by P-selectin. We describe here a panel of monoclonal antibodies p repared against high molecular weight fractions of HL-60 cell membrane s. These antibodies are of IgM isotype, bind to a similar to 240-kDa p rotein from human leukocyte membranes which is also reactive with P-se lectin. They recognize a Ca2+-dependent, sialidase-sensitive determina nt on myeloid and monocytoid cell lines. Each antibody specifically in hibits adhesion of neutrophils or HL-60 cells to: 1) purified P-select in, 2) thrombin-stimulated platelets, and 3) phorbol 12-myristate 13-a cetate-activated endothelial cells. These results suggest that the sia loglycoprotein recognized by this panel of monoclonal antibodies may f unction as a cell surface ligand for P-selectin.