Human L-Selectin (leukocyte selectin, CD62L, LAM-1, LECAM-1, LECCAM-1, TQ1, Leu-8, DREG, lymph node homing receptor, MEL-14 antigen) is a cell surface glycoprotein expressed constitutively on a wide variety of leukocytes. Two forms of Soluble L-Selectin (sL-Selectin) have been reported. sL-Selectin derived from lymphocytes is about 62 kDa, while the fragment derived from neutrophils is 75-100 kDa. sL-Selectin can inhibit the binding of lymphocytes to endothelium at high concentrations, suggesting a possible role in modulating this binding in vivo. Monitoring of sL-Selectin levels in serum provides more detailed insights in several pathological situations such as sepsis and acquired immune deficiency syndrome (AIDS).