SerpinD1, also known as heparin cofactor II(HC-II), is a member of Serpin superfamily of the serine proteinase inhibitors. It is a single chain glycoprotein with a size of 66.5 kDa and is secreted from hepatocytes. HC-II acts as a thrombin inhibitor in the coagulation cascade, in a glycosaminoglycan-dependent pathway using the release of a sequestered hirudin-like N-terminal tail for interaction with thrombin. This serpin belongs to multiple member group V2 of vertebrate serpin classification. It has been suggested that HC-II is a predictor of decreased atherosclerosis in the elderly and protective against atherosclerosis in mice. HCII can used as a predictive biomarker and therapeutic target for atherosclerosis.