Neonatal neutrophil interaction with P-selectin: contribution of P-selectin glycoprotein ligand-1 and sialic acid

Previously we had determined that neonatal neutrophils had decreased intera ction with monolayers expressing P-selectin compared to adult cells. In thi s study we examined the function of neonatal P-selectin glycoprotein ligand -l (PSGL-1), A rabbit polyclonal antibody directed against the amino termin us of human PSGL-1 was produced and purified (3RB-PSGL-1), Neonatal neutrop hils expressed the epitope recognized by 3RB-PSGL-1 and expression was decr eased compared with adult neutrophils (20%, P < 0.05). In addition neonatal neutrophils had decreased interaction with Chinese hamster ovary (CHO)-P-s electin under both shear conditions and static adhesion (P < 0.05), Treatme nt of both neonatal and adult neutrophils with 3RB-PSGL-1 similarly inhibit ed the interaction with P-selectin monolayers under shear conditions, effec ts similar to treatment with O-sialoglycoprotein endopeptidase (OSGE). Neur aminidase treatment of neonatal and adult cells also markedly inhibited the interaction. In a detachment assay marked differences were noted between n eonatal and adult cells treated with either 3RB-PSGL-1 or neuraminidase. Su ch treatments had little effect on adult neutrophils until shear stress exc eeded 2.8 dynes/cm(2). Treated neonatal neutrophils were exquisitely sensit ive to shear stress with a marked decrease in interaction noted at a shear stress as low as 0.6 dynes/cm(2). Thus the adhesive mechanisms that remain after treatment with neuraminidase or 3RB-PSGL-1 have a relatively low avid ity and function less well in neonatal neutrophils compared to adult neutro phils, We speculate that this may account for the less efficient adhesion o f neonatal neutrophils to P-selectin under conditions of flow.