['The antiphospholipid syndrome (APS) is an acquired autoimmune disorder predisposing patients to thrombosis or pregnancy complications. Since inverted erythrocyte membranes (iEMs) might provide a physiologically relevant source of anionic phospholipids, we studied the interactions of phospholipid-binding proteins and APS antibodies using iEMs.', 'iEMs were prepared from packed erythrocytes by hypotonic lysis. Phosphatidylserine (PS) exposure was confirmed by annexin A5 (A5) binding using fluorescence microscopy and flow cytometry. Binding of β', 'iEMs readily precipitated purified β'] Do inverted erythrocyte membranes demonstrate β2GPI-antiphospholipid antibody interactions and membrane crosslinking?