Arp2/3 complex incorporation into the cytoskeleton of the active WAS platelet.

Platelets isolated from WAS patient P50 were activated by centrifugation onto poly-l-lysine–coated glass coverslips and permeabilized with 0.75% Triton X-100 in PHEM buffer. Cytoskeletons were labeled with a mixture of rabbit polyclonal anti-Arp3 and anti–p34-Arc antibodies and 10 nm colloidal gold coated with goat antirabbit IgG. Cytoskeletons were fixed, washed into water, rapidly frozen, freeze-dried, and metal- coated. Bars represent 2 μm (A) and 200 nm (B,C). Lm indicates lamellae; f, filopodia; arrows, foci of gold labeling.