L-selectin, also known as CD62L, is a cell adhesion molecule found on the cell surface of leukocytes, and the blastocyst. It is coded for in the human by the SELL gene. L-selectin belongs to the selectin family of proteins, which recognize sialylated carbohydrate groups containing a Sialyl LewisX (sLeX) determinant.[5] L-selectin plays an important role in both the innate and adaptive immune responses by facilitating leukocyte-endothelial cell adhesion events.[6] These tethering interactions are essential for the trafficking of monocytes and neutrophils into inflamed tissue as well as the homing of lymphocytes to secondary lymphoid organs. L-selectin is also expressed by lymphoid primed hematopoietic stem cells and may participate in the migration of these stem cells to the primary lymphoid organs.[6] In addition to its function in the immune response, L-selectin is expressed on embryonic cells and facilitates the attachment of the blastocyst to the endometrial endothelium during human embryo implantation.[7]
L-selectin is composed of multiple structural regions: an N-terminus C-type lectin domain, an adjacent epidermal growth factor-like domain, two to the consensus repeat units homologous to those found in C3/C4-binding proteins, an extracellular cleavage site, a short transmembrane domain, and a cytoplasmic tail. It is cleaved by ADAM17.[6][8]
