Autoantibodies to α_IIbβ₃ in patients with chronic immune thrombocytopenic purpura bind primarily to epitopes on α_IIb

Chronic immune thrombocytopenic purpura (ITP) is an autoimmune disease caused by platelet destruction resulting from autoantibodies against platelet surface proteins, particularly platelet glycoprotein IIb/IIIa (α_IIbβ₃). TO localize the autoepitopes on platelet α_IIbβ₃, the binding of autoantibodies to Chinese hamster ovary (CHO) cells expressing either α_IIbβ₃ or α_vβ₃ was studied. Thirteen of 14 ITP autoantibodies bound only to CHO cells expressing α_IIbβ₃. Because these 2 integrins have the same beta chain (β₃), these results show that most epitopes in chronic ITP are dependent on the presence of glycoprotein α_IIb.