Anti-phospholipid antibodies (aPL) and apoptosis: prothrombin-dependent aPL as a paradigm for phospholipid-dependent interactions with apoptotic cells.

The natural targets of anti-phospholipid antibodies (aPL) and the stimuli that induce them remain unknown. Apoptotic cells have been proposed as both potential targets and immunogens for anti-phospholipid antibodies. Demonstration of selective recognition by anti-phospholipid antibodies provides support for apoptotic cells as antigenic targets.

Prothrombin binds to the surface of apoptotic, but not viable, cells and serves as a target of lupus anticoagulant autoantibodies.

Anti-phospholipid Ab (aPL) are a heterogeneous group of autoantibodies directed against various combinations of phospholipids (PL) and PL-binding proteins. Lupus anticoagulant (LA) Ab, a subset of aPL, exhibit anticoagulant properties in vitro, but are procoagulant in vivo. Most LA Ab are specific for either beta(2)-glycoprotein I (beta(2)GPI) or prothrombin (PT), two PL-binding proteins.