FUNCTIONAL-CHARACTERIZATION OF L-SELECTIN LIGANDS ON HUMAN NEUTROPHILS AND LEUKEMIA-CELL LINES - EVIDENCE FOR MUCINLIKE LIGAND ACTIVITY DISTINCT FROM P-SELECTIN GLYCOPROTEIN LIGAND-1

Recent reports have shown that leukocyte-leukocyte adhesion is depende nt on L-selectin and that leukocyte recognition of L-selectin may be m ediated by P-selectin glycoprotein ligand-1 (PSGL-1). We show that the specific attachment and rolling of human neutrophils and the leukemia cell lines HL-60 and U937 on immobilized, purified L-selectin under c ontinuous shear stress is only partially inhibited by treatment with t he PSGL-1 monoclonal antibody (MoAb), KPL1 (41% to 53% inhibition), su ggesting that L-selectin ligand activity in addition to PSGL-1 may med iate myeloid cell rolling on L-selectin. K562 cells cotransfected with cDNAs encoding alpha(1,3)fucosyltransferase-VII (FucT-VII) and PSGL-1 rolled on L-selectin. Adhesion of FucT-VII-PSGL-1 transfectants to L- selectin was completely blocked by MoAb KPL1, indicating that both L-s electin and P-selectin bind similar sites on PSGL-1. In support of exi stence of a non-PSGL-1 L-selectin ligand activity on leukocytes, an HL -60 membrane preparation immunodepleted of PSGL-1 supported rolling of L-selectin, but not P-selectin transfectants. Treatment of HL-60 cell s with O-sialoglycoprotein endopeptidase inhibited attachment and roll ing on L-selectin and P-selectin. However, neuraminidase treatment com pletely blocked HL-60 rolling on L-selectin, but not P-selectin, sugge sting L-selectin and P-selectin ligand activities have different contr ibutions of sialic acid. These findings indicate that myeloid cells ex press sialylated, O-linked glycoprotein ligand activity independent of PSGL-1 that supports L-selectin-mediated rolling. (C) 1998 by The Ame rican Society of Hematology.