Immunoprecipitation analysis of platelet GPIIb and GPIIIa from the proband, her mother, father, and sister. Proteins in total platelet lysates were labeled with biotin-NHS, and GPIIb-IIIa complexes were immunoprecipitated using MoAbs specific for GPIIIa (P37) or GPIIb (M3) and processed as described in Materials and Methods.