Table 1.

Adhesion receptors mediating neutrophil rolling and tethering in vivo and in vitro.

Receptor	Extracellular length (nm)	Expression	Molecular Density	Role in leukocyte recruitment	Physiological ligand
Hu P-selectin	38	Inducible	20-50 molecules/μm2 on cultured HUVEC	Tethering and rolling	PSGL-1 on neutrophils, monocytes, and Th1 cells*
Mu P-selectin	34	Inducible	No data	Tethering and rolling	PSGL-1 on neutrophils, monocytes and Th1 cells*
Hu E-selectin	27	Inducible	750 molecules/μm2 on cultured HMVEC	Slow rolling	PSGL-1, sialylated glycosphingolipids, and sLex bearing glycoproteins on neutrophils
Mu E-selectin	27	Inducible	No data	Slow rolling	PSGL-1, ESL-1, CD44, and core O-derived glycans bearing glycoproteins on neutrophils
Hu L-selectin	12	Constitutive	Neutrophils (30,000-40,000 molecules), monocytes, lymphocytes	Tethering, secondary capture, and rolling (only in HEVs)	PSGL-1 on neutrophils and monocytes, PNAds (GlyCAM-1, CD34, and podocalyxin) on EC in HEVs of lymph nodes
Mu L-selectin	12	Constitutive	Neutrophils, monocytes, lymphocytes	Tethering, secondary capture, and rolling (only in HEVs)	PSGL-1 on neutrophils and monocytes, PNAds (GlyCAM-1, CD34, and podocalyxin) on EC in HEVs of lymph nodes
Hu PSGL-1	50	Constitutive	Neutrophils (18,000-25,000 molecules), monocytes, Th1 cells*	Tethering, rolling, and secondary capture	P- and E-selectin on EC and L-selectin on neutrophils, and monocytes
Mu PSGL-1	50	Constitutive	Neutrophils (75,000 molecules), monocytes, Th1 cells*	Tethering, rolling, and secondary capture	P- and E-selectin on EC and L-selectin on neutrophils, and monocytes

Hu, human; Mu, murine; HUVEC, human umblical-cord vascular endothelial cells; HMVEC, human micro-vascular endothelial cells; HEVs, high endothelial venules; PSGL-1, P-selectin glycoprotein ligand-1; ESL-1, E-selectin ligand-1; sLe^x, sialyl Lewis x; EC, endothelial cells.

^*PSGL-1 is expressed on other leukocytes, but is correctly glycosylated only on myeloid cells and Th1 cells.