CD59 glycoprotein, also known as MAC-inhibitory protein (MAC-IP), membrane inhibitor of reactive lysis (MIRL), or protectin, is a protein that in humans is encoded by the CD59 gene. It belongs to the LY6/uPAR/alpha-neurotoxin protein family. CD59 attaches to host cells via a glycophosphatidylinositol (GPI) anchor.