GP1BA and autoimmune thrombocytopenic purpura: Our results are consistent with previous reports that the presence of platelet-associated anti-GPIb antibodies was associated with inadequate responses to corticosteroids and IVIG in ITP patients.17,18 Nieswandt and colleagues demonstrated that anti-GPIba monoclonal antibodies induced profound thrombocytopenia by Fc-independent mechanisms.19 Platelet activation and apoptosis induced by anti-GPIba antibodies are critical in the Fc-independent platelets clearance while anti-GPIIb/IIIa antibodies induced platelets clearance mainly by Fc-dependent phagocytosis.