<s>[INST] context: The conformational change in glycoprotein IIb/IIIa that occurs with platelet activation allows binding of fibrinogen, a large bivalent plasma polypeptide that forms bridges between adjacent platelets, leading to their aggregation. Predictably, inherited deficiency of GpIIb-IIIa results in a bleeding disorder called Glanzmann thrombasthenia. Bernard-Soulier syndrome illustrates the consequences of defective adhesion of platelets to subendothelial matrix. Bernard-Soulier syndrome is caused by an inherited deficiency of the platelet membrane glycoprotein Complex Ib-IX. This glycoprotein is a receptor for vWF and is essential for normal platelet adhesion to the subendothelial extracellular matrix. Affected patients have a variable, often severe, bleeding tendency. Factor VIII and vWF are encoded by separate genes and are synthesized in different cells. Factor VIII is an essential cofactor of factor IX, which conves factor X to factor Xa. It is made in several tissues; sinusoidal endothelial cells and Kupffer cells in the liver seem to be major sources. Type 1 and type 3 von Willebrand disease are associated with quantitative defects in vWF. Type 1, an autosomal dominant disorder characterized by a mild to moderate vWF deficiency, accounts for about 70% of all cases. Type 2 von Willebrand disease is characterized by qualitative defects in vWF. [/INST] question: Glanzmann thromasthenia is due to defect in:- | options: A: Gp IIb/IIIa B: Gp Ib-IX C: CD68 D: Von Willebrand factor | answer: A </s>