Phagocytosed platelets reach intracellular acidic vacuoles. (A) Neutrophils were incubated with resting or activated platelets labeled with BCECF-AM for 5 minutes at 37°C or 4°C and analyzed by flow cytometry. A bright-red fluorescence associated with the phagocytic events indicates that intracellular platelets reached acidic vacuoles. Platelet acidification did not occur in conditions in which phagocytosis did not occur (ie, when neutrophils were challenged with resting platelets or when the assay was carried out at 4°C). (B) Neutrophils were incubated with resting or activated platelets labeled with pHrodo for 5 minutes at 37°C or 4°C and analyzed by flow cytometry. A bright-red fluorescence associated with the phagocytic events indicates that platelets reached acidic vacuoles. Acidification did not occur in conditions in which phagocytosis did not occur (ie, when neutrophils were challenged with resting platelets or when the assay was carried out at 4°C).