Evidence for a third component in neutrophil aggregation: potential roles of O-linked glycoproteins as L-selectin counter-structures.
The homotypic aggregation of neutrophils requires the participation of L-selectin and the beta 2-integrins, but it has not been clear whether the two receptors recognize one another as counter-structures or whether other adhesion molecules are involved. We have examined aggregation of live neutrophils with target populations, manipulated to alter expression of adhesive epitopes, using flow cytometry. A target population depleted of both L-selectin and activatable beta 2-integrin displayed an ability to aggregate with live neutrophils, suggesting that these two molecules are not counter-structures. We also found that an O-sialoglycoprotease (GCP) from Pasteurella haemolytica is capable of inhibiting homotypic aggregation. Neutrophils treated with GCP lose O-glycosylated proteins but retain L-selectin and activatable beta 2-integrin. One or more of the GCP substrates appears to function in L-selectin-dependent binding but not in beta 2-integrin-dependent binding. Together the data suggest a mechanism of aggregation that is analogous to leukocyte-endothelial cell adhesion in which a low-affinity carbohydrate-dependent interaction precedes a high-affinity integrin-dependent adhesion.
Bennett
T A
TA
Department of Pathology, University of New Mexico, School of Medicine, Albuquerque 87131, USA.
Schammel
C M
CM
Lynam
E B
EB
Guyer
D A
DA
Mellors
A
A
Edwards
B
B
Rogelj
S
S
Sklar
L A
LA
D015815:Cell Adhesion Molecules / Q000378:metabolism*; D002449:Cell Aggregation; D002634:Chemotaxis, Leukocyte; D006801:Humans; D066298:In Vitro Techniques; D007461:Iodoacetates / Q000494:pharmacology; D019807:Iodoacetic Acid; D019041:L-Selectin / Q000378:metabolism*; D008024:Ligands; D009504:Neutrophils / Q000166:cytology*; D011956:Receptors, Cell Surface / Q000378:metabolism; D012795:Sialoglycoproteins / Q000378:metabolism*; D013439:Sulfhydryl Reagents / Q000494:pharmacology
D015815:Cell Adhesion Molecules; D007461:Iodoacetates; D008024:Ligands; D011956:Receptors, Cell Surface; D012795:Sialoglycoproteins; D013439:Sulfhydryl Reagents; D019041:L-Selectin; D019807:Iodoacetic Acid