Anti-β2GPI/HLA-DR antibodies are detected by a ‘cell-based assay’ using 293T cells co-transfected with β2GPI and HLA-DR.51 Since almost half of the APS patients were single positive for anti-β2GPI/HLA-DR antibodies, while negative for anti-β2GPI and aCL, β2GPI/HLA-DR complexes may expose unique epitopes that are not present on plate-bound β2GPI or β2GPI/CL complexes. The gene discussed is APOH; the disease is autoimmune polyendocrinopathy.