P-SELECTIN GLYCOPROTEIN LIGAND-1 MEDIATES ROLLING OF HUMAN NEUTROPHILS ON P-SELECTIN

Neutrophils roll on P-selectin expressed by activated platelets or end othelial cells under the shear stresses in the microcirculation. P-sel ectin glycoprotein ligand-l (PSGL-1) is a high affinity ligand for P-s electin on myeloid cells. However, it has not been demonstrated that P SGL-1 contributes to the rolling of neutrophils on P-selectin. We deve loped two IgG mAbs, PL1 and PL2, that appear to recognize protein-depe ndent epitopes on human PSGL-1, The mAbs bound to PSGL-1 on all leukoc ytes as well as on heterologous cells transfected with PSGL-1 cDNA. PL 1, but not PL2, blocked binding of I-125-PSGL-1 to immobilized P-selec tin, binding of fluid-phase P-selectin to myeloid and lymphoid leukocy tes, adhesion of neutrophils to immobilized P-selectin under static co nditions, and rolling of neutrophils on P-selectin-expressing CHO cell s under a range of shear stresses, PSGL-1 was localized to microvilli on neutrophils, a topography that may facilitate its adhesive function . These data indicate that (a) PSGL-1 accounts for the high affinity b inding sites for P-selectin on leukocytes, and (b) PSGL-1 must interac t with P-selectin in order for neutrophils to roll on P-selectin at ph ysiological shear stresses.