CD62L, also known as L-selectin, is a type I transmembrane glycoprotein with lectin-like and Epidermal Growth Factor-like domains.1, 2 It binds to sialylated oligosaccharide determinants on high endothelial venules (HEV) in peripheral lymph nodes.1, 2 In the mouse, CD62L is expressed on most thymocytes and on peripheral leukocytes, including B and T lymphocytes, neutrophils, monocytes and eosinophils.3-7 This member of the selectin family of cell adhesion molecules appears to be required for lymphocyte homing to peripheral lymph nodes and for leukocyte extravasation at sites of inflammation.1, 2, 7-9 Expression of CD62L on lymphocytes and neutrophils is rapidly down-regulated upon cell activation and the level of CD62L expression, along with other markers, distinguishes naive T cells from effector/memory T cells.10-13 The monoclonal antibody blocks in vitro binding of lymphocytes to peripheral lymph node HEV and inhibits in vivo lymphocyte extravasation into peripheral lymph nodes and the late stages of leukocyte rolling.1, 2, 7-9