Goat Anti-Human Apolipoprotein-H polyclonal antibody for IEP, ELISA. Apolipoprotein-H, also known as ?2-Glycoprotein I (?2GPI), is a plasma glycoprotein that circulates at a concentration of 200 ug/ml (4 ?M). Synthesized in the liver, ?2GPI is a single chain molecule of 48 kDa, consisting of five repeating internally disulphide-bonded structures referred to as sushi domains. Relative to other glycoproteins, ?2GPI has an unusually high content of cysteine (6.2%), proline (8.3%) and carbohydrate (19%). Almost half the circulating ?2GPI in plasma is associated with lipoproteins of all major fractions. ?2GPI has been demonstrated to bind negatively charged phospholipids, heparin and platelets. Although the precise function(s) are as yet unknown, ?2GPI has been demonstrated to interfere with blood coagulation by competitively binding to negatively charged phospholipid surfaces exposed during cell activation or damage. Recent evidence also implicates ?2GPI as a cofactor recognized by anti-phospholipid antibodies present in some autoimmune disorders such as systemic lupus erythematosus (SLE).