Following posttranslational modification, β2GPI undergoes conformational change that exposes the major B-cell binding site on domain I and the major T-cell binding site on domain V. Thus, the proportion of free thiol β2GPI and oxidized β2GPI is important to the development of anti-β2GPI autoantibodies in APS. This evidence concerns the gene APOH and autoimmune polyendocrinopathy.