CD59 is a cell surface glycoprotein that regulates complement-mediated cell lysis, and it is involved in lymphocyte signal transduction located on the surface of leukocytes, vascular endothelial cells, various epithelial cells, and the placenta, playing a crucial role in immune regulation. CD59′s strategic location on cell membranes is vital as CD59 acts as a protective agent against the complement system, preventing the formation of the membrane attack complex (MAC) that can lead to cell lysis. By binding to the C8 and C9 components of the MAC, CD59 effectively inhibits the lytic pore formation, thereby safeguarding host cells from complement-mediated damage. Additionally, CD59 is involved in modulating calcium release and activating lipid-raft associated signaling molecules, including tyrosine kinases, which are essential for various cellular processes.