Aggregation of GPVI-deficient and control platelets induced by (A) collagen type I, (B) CRP-XL, and (C) ADP. The platelet count had to be adjusted to 1.8 × 10⁸/mL because the patient was slightly thrombocytopenic. Collagen and CRP-XL did not induce platelet aggregation in GPVI-deficient platelets, although these platelets were able to aggregate in response to ADP. Data shown are representative of three similar experiments.