Neutrophil-neutrophil interactions under hydrodynamic shear stress involve L-selectin and PSGL-1. A mechanism that amplifies initial leukocyte accumulation of P-selectin in vitro.
Leukocytes attach to and roll on inflamed endothelium and on leukocyte monolayers that form on the endothelial cells. Leukocyte-leukocyte interactions occurring under hydrodynamic shear stress are mediated by binding of L-selectin to unknown sialomucin-like glycoproteins. We show that purified neutrophil PSGL-1, a sialomucin glycoprotein that serves as a ligand for both P- and E-selectin, can also support the attachment and rolling of free flowing neutrophils in vitro. Neutrophil rolling on PSGL-1 was abolished by the anti-L-selectin mAb DREG200 and by the anti-PSGL-1 mAb PL1, indicating that L-selectin can interact directly with PSGL-1. Neutrophil rolling on neutrophil monolayers was also blocked by PL1 (60 +/- 9% SEM inhibition); however, DREG200 blocked more efficiently (93 +/- 7% SEM inhibition), suggesting that other L-selectin ligands may exist on the neutrophil surface. These studies demonstrate that PSGL-1 on the neutrophil surface is a major functional ligand for L-selectin. The avidity of this L-selectin-dependent adhesion event was sufficient to allow individual neutrophils rolling on P-selectin to capture free flowing neutrophils, which progressed to form linear strings and discrete foci of rolling neutrophils. Neutrophil accumulation on P-selectin accelerated with time as a result of neutrophil-assisted capture of free flowing neutrophils. When neutrophil-neutrophil interactions were blocked by DREG200, neutrophils accumulated on P-selectin in a random pattern and at a uniform rate. Thus, leukocyte-assisted capture of flowing leukocytes may play an important role in amplifying the rate of initial leukocyte recruitment at sites of inflammation.
Walcheck
B
B
Department of Immunology, Boehringer Ingelheim Pharmaceuticals, Inc., Ridgefield, Connecticut 06877, USA.
Moore
K L
KL
McEver
R P
RP
Kishimoto
T K
TK
D000911:Antibodies, Monoclonal / Q000494:pharmacology; D055592:Biophysical Phenomena; D001703:Biophysics; D002448:Cell Adhesion / Q000187:drug effects / Q000502:physiology*; D006801:Humans; D019041:L-Selectin / Q000276:immunology / Q000378:metabolism*; D008024:Ligands; D008562:Membrane Glycoproteins / Q000378:metabolism*; D009068:Movement; D009077:Mucins / Q000378:metabolism*; D009504:Neutrophils / Q000502:physiology*; D010784:Photomicrography
D000911:Antibodies, Monoclonal; D008024:Ligands; D008562:Membrane Glycoproteins; D009077:Mucins; C084882:P-selectin ligand protein; D019041:L-Selectin