Beta-2 glycoprotein 1 (beta-2 GP1, also called apolipoprotein H) is a 326-amino acid polypeptide synthesized by hepatocytes, endothelial cells and trophoblast cells.. The persistent presence of IgG and/or IgM beta 2 glycoprotein I (B2GPI) antibodies (greater than 99th percentile) is a laboratory criterion for the diagnosis of antiphospholipid syndrome (APS).. Clinical Information. Beta-2 glycoprotein 1 (beta-2 GP1, also called apolipoprotein H) is a 326-amino acid polypeptide synthesized by hepatocytes, endothelial cells, and trophoblast cells.. Apolipoprotein H (Apo-H), previously known as β 2-glycoprotein I and beta-2 glycoprotein I, is a 38 kDa multifunctional apolipoprotein that in humans is encoded by the APOH gene . Useful For. Evaluation of patients with suspected antiphospholipid syndrome by identification of beta-2 glycoprotein 1 (beta-2 GP1) IgG and IgM antibodies. Beta-2-Glycoprotein 1 (also known as apolipoprotein H), is a cofactor in antiphospholipid antibody binding and is the critical antigen in the antiphospholipid antibody syndrome. The presence of high titer IgG/IgM beta-2-glycoprotein 1 antibodies is one criteria for the diagnosis of antiphospholipid antibody syndrome..