GP9 and autoimmune thrombocytopenic purpura: Platelet-FcγRIIa is not only crucial for the pathogenesis of HIT, but may also play a role in immune thrombocytopenia (ITP) [64], an autoimmune disease characterized by autoantibody production by B cells directed mainly against GPIb/GPIX and αIIbβ3-integrin [65].