Fluorescent analysis was performed on a flow cytometer (FACSCalibur, BD Bioscience). The samples were acquired using the CellQuest v3.3 software with at least 30,000 platelets. The platelets population was gated on the basis of cells size (lower forward scatter), cells refrangibility (lower side scatter) and positive CD41 antigen characteristics (Figure 1A, B). The median fluorescence intensity (MFI) of ABO antigens on platelets was measured by CellQuest v3.3 software [12].