L-Selectin (also known as Leukocyte Selectin, LAM‑1, LECAM-1, LECCAM-1, TQ1, Leu-8, MEL-14 antigen, DREG, lymph node homing receptor, CD62L), a member of the Selectin family, is a cell surface glycoprotein expressed constitutively on a wide variety of leukocytes. Two forms of L‑Selectin have been reported, apparently arising as a result of post-translational modifications. The lymphocyte form shows an apparent molecular weight of 74 kDa, while the neutrophil form is 90 - 100 kDa. Human and mouse L‑Selectin share 76% amino acid (aa) sequence homology.
L‑Selectin plays a role in the migration of lymphocytes into peripheral lymph nodes and sites of chronic inflammation, and of neutrophils into acute inflammatory sites. Acting in cooperation with P-Selectin and E-Selectin, L‑Selectin mediates the initial interaction of circulating leukocytes with endothelial cells that produces a characteristic "rolling" of the leukocytes on the endothelium. This initial interaction, also involving ICAM-1 and VCAM-1, leads eventually to extravasation of the white blood cell through the blood vessel wall into the extracellular matrix tissue.
ELISA techniques have shown that detectable levels of soluble L‑Selectin are present in the biological fluids of apparently normal individuals. Furthermore, a number of studies have reported that levels of L‑Selectin may be elevated or lowered in subjects with a variety of pathological conditions.
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