Deficiency of Intact Thrombospondin and Membrane Glycoprotein La in Platelets With Defective Collagen - Induced Aggregation and Spontaneous Loss of Disorder

Platelets from a patient with a severe lifelong bleeding tendency. which later spontaneously disappeared, lacked intact thrombospondin and glycoprotein (GP) Ia. Before disappearance of the bleeding disorder, results of coagulation studies and platelet aggregation in response to adenosine diphsophate (ADP). arachidonic acid. thrombin. A231 87, epinephrine. and ristocetin were normal. In contrast. aggregation only occurred in the presence of collagen or wheat germ agglutinin at unusually high doses of these agonists. The platelets adhered normally to purified bovine and human type I collagen. and they did not spread in the presence of methylated type I collagen. No collageninduced clot retraction was observed. Two-dimensional gel