P-selectin glycoprotein ligand-1 mediates L-selectin-dependent leukocyte rolling in venules.
Leukocyte rolling in postcapillary venules of inflamed tissues is reduced in L-selectin-deficient mice and mice treated with L-selectin blocking antibodies, but the glycoprotein ligand for L-selectin in inflamed venules is unknown. Here, we show that L-selectin-dependent rolling after P-selectin blockade is completely absent in P-selectin glycoprotein ligand-1 (PSGL-1)-/- mice or wild-type mice treated with a PSGL-1 blocking monoclonal antibody. Immunohistochemistry and flow cytometry failed to show PSGL-1 expression on resting or inflamed endothelium or on platelets. To investigate whether leukocyte-expressed PSGL-1 is mediating L-selectin-dependent rolling, we reconstituted lethally irradiated wild-type mice with PSGL-1-/- bone marrow cells. These chimeric mice showed no L-selectin-dependent rolling, suggesting that leukocyte-expressed PSGL-1 mediates L-selectin-dependent rolling. Frame-to-frame video analysis of L-selectin-dependent rolling in wild-type mice showed that the majority of observed L-selectin-dependent leukocyte rolling was between free flowing leukocytes and already adherent leukocytes or possibly leukocyte fragments, followed by E-selectin-dependent leukocyte rolling along the endothelium. Leukocyte rolling was significantly slower for leukocyte-endothelial than leukocyte-leukocyte interactions. We conclude that leukocyte-expressed PSGL-1 serves as the main L-selectin ligand in inflamed postcapillary venules. L-selectin binding to PSGL-1 initiates tethering events that enable L-selectin-independent leukocyte-endothelial interactions. These findings provide a molecular mechanism for the inflammatory defects seen in L-selectin-deficient mice.
Sperandio
Markus
M
University of Virginia Health System, Cardiovascular Research Center, MR5 Bldg, Rm. 1013, P.O. Box 801 394, Charlottesville, VA 22908-1394, USA.
Smith
Michael L
ML
Forlow
S Bradley
SB
Olson
Timothy S
TS
Xia
Lijun
L
McEver
Rodger P
RP
Ley
Klaus
K
D000818:Animals; D002450:Cell Communication; D007249:Inflammation / Q000276:immunology*; D019041:L-Selectin / Q000502:physiology*; D007962:Leukocytes / Q000502:physiology*; D008562:Membrane Glycoproteins / Q000502:physiology*; D051379:Mice; D019007:P-Selectin / Q000502:physiology; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology; D014699:Venules / Q000473:pathology*
D008562:Membrane Glycoproteins; D019007:P-Selectin; C084882:P-selectin ligand protein; D014409:Tumor Necrosis Factor-alpha; D019041:L-Selectin