Biological or Clinical Significance:
E-Selectin (Endothelial Leukocyte Adhesion Molecule-1, ELAM-1, CD62E) is a 115 kDa, type-1 transmembrane glycoprotein expressed only on endothelial cells and only after activation by inflammatory cytokines (IL-1 P, TNF-a) or endotoxin. Expression is transitory, reaching a maximum within about 6 hours after stimulation and then declining, with shedding of soluble E-Selectin. Cell-surface E-Selectin is a mediator of the rolling attachment of leukocytes to the endothelium, an essential step in extravasation of leukocytes at the site of inflammation, thereby playing a key role in localized inflammatory response. E-Selectin is believed to be particularly important in inflammation involving the skin.
The extracellular part of E-Selectin includes a calcium-dependent C2-type lectin domain, an epidermal growth factor (EGF) domain, and six repeats of a complement-regulatory-protein-like sequence. E-Selectin binds sialyl Lewis X (sLex), a sialic acid-galactose-Nacetylglucosamine-fructose tetrasaccharide, but the actual recognition is thought to be for a specific presentation of those glycosyl units in a precise three-dimensional configuration on a specific glycoprotein rather than for that particular carbohydrate.
Soluble E-Selectin is found in the blood of healthy individuals, probably arising from proteolytic cleavage of the surface-expressed molecule. Elevated levels of sE-Selectin in serum have been reported in a variety of pathological conditions. Although it might be anticipated that sE-Selectin would suppress leukocyte migration by competing with surface-associated E-Selectin, it may actually activate neutrophils and act as a pro-inflammatory agent.
Principle of Test Method:
The e-selectin assay is a solid phase ELISA designed to measure soluble e-selectin in cell culture supernates, serum, and plasma.