CD14 is a GPI-anchored molecule expressed by virtually all human monocytes and macrophages and – to a lesser degree - granulocytes. CD14 together with Toll-like receptor 4 and MD-2 forms the LPS-receptor complex that recognizes and signals the presence of LPS. While CD14 has no signaling structure its main role seems to be the binding of LPS. The MEM18 antibody permits the identification and enumeration of leukocytes using flow cytometry. MEM18 has been also used for functional studies since this antibody blocks the interaction of LPS with CD14 on monocytes.