GPIbα-IX complex formation in BSS platelets.

Washed platelets from healthy volunteers (A-D) and the patient with BSS (E-H) were plated onto glass slides precoated with fibrinogen (20 μg/mL) and allowed to adhere for 1 hour at room temperature. Platelets were then either permeabilized with ice-cold methanol and acetone before staining (A, B and E, F) or stained directly without permeabilizing (C, D and G, H). Slides were stained for GPIbα-IX with the mAb AK1. Platelets were imaged in parallel in fluorescent (A, C, E, and G) and differential-interference contrast (DIC) mode (B, D, F, and H). The platelets were permeabilized to allow antibody probes to react with cytoplasmic epitopes. Data are presented as paired images separated to show AK1 staining with an Alexa 546–conjugated antimouse antibody or DIC images to indicate the platelet position in the nonstaining cells. One image is shown for each treatment; this is representative of 3 independent experiments in which more than 20 platelets were analyzed. GPIbα-IX complex was present in the cytoplasm and on the surface of normal platelets (A, C) but absent from BSS platelets (E, G). The DIC images show the larger size of the BSS platelets.