L-Selectin (also known as Leukocyte Selectin, LAM‑1, LECAM-1, LECCAM-1, TQ1, Leu-8, MEL-14 antigen, DREG, lymph node homing receptor, and 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 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 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.