The endogenous lectin of human platelets is an alpha-granule component.
Platelets from patients with several bleeding disorders (congenital afibrinogenemia, Glanzmann's thrombasthenia, gray platelet syndrome, and Hermansky-Pudlak syndrome) were evaluated for both platelet-bound and platelet-free hemagglutination activities. Thrombin and A23187 activated afibrinogenemic, Hermansky-Pudlak, and thrombasthenic platelets had normal platelet-bound hemagglutination activity. Gray platelets activated by the same agents had deficient platelet-bound hemagglutination activity. In contrast, thrombin-activated afibrinogenemic, gray, and thrombasthenic platelets lacked platelet-free hemagglutination activity. Only thrombin-activated Hermansky-Pudlak platelets had a normal level of platelet-free hemagglutination activity. On the basis of these results and the distinguishing characteristics of the defective platelets, it is concluded that the alpha-granules are the origin of the enhanced hemagglutination activity. Furthermore, it is suggested that the insufficiency of the platelet-bound agglutinin may be the cause of the inability of gray platelets to aggregate normally in response to thrombin.
D001778:Blood Coagulation Disorders / Q000276:immunology*; D001792:Blood Platelets / Q000276:immunology*; D003594:Cytoplasmic Granules / Q000032:analysis*; D004591:Electrophoresis, Polyacrylamide Gel; D006384:Hemagglutination; D006386:Hemagglutination Tests; D006801:Humans; D037102:Lectins / Q000097:blood*; D013917:Thrombin
D037102:Lectins; D013917:Thrombin