The present invention provides a glycoprotein derived from human cell membrane, which has a molecular weight of 20 to 25 Kd as estimated by SDS polyacrylamide gel electrophoresis, and contains N-glycoside type carbohydrate chain and phosphatidylinositol, and possesses an inhibitory activity to complement.mediated cell membrane damage. The present invention further provides a gene coding for the glycoprotein, and a method for the production of the glycoprotein and the gene therefor.