Alboaggregin A–induced platelet procoagulant activity, α-granule release, and the effect of Abs against GPIb and GPVI.

(A) Gel-filtered platelets were preincubated with or without mAb SZ2 (20 μg/mL), mAb VM16d (20 μg/mL), or Fab fragments of anti-GPVI Abs. After treatment with alboaggregin A (0.05-2.5 mg/mL) and annexin V-FITC, the fluorescence of 5000 platelets per measuring point was determined by flow cytometry. (B) Gel-filtered platelets were preincubated with or without mAb SZ2 (20 μg/mL) or Fab fragments of anti-GPVI Abs. After treatment with alboaggregin A (0.1-2.5 mg/mL), fixation with formaldehyde, and addition of FITC-labeled anti-CD62P mAb, the fluorescence of 5000 platelets per measuring point was determined by flow cytometry. Data are the mean results from 3 experiments using platelets from different donors. ● 25 000 platelets/μL, ○ 25 000 platelets/μL in the presence of mAb SZ2, ■ 25 000 platelets/μL in the presence of mAb VM16d, and ▵ 25 000 platelets/μL in the presence of Fab fragments of anti-GPVI Abs.