FIG. 1.

Platelet FcγRIIA mediates binding of IgG-coated targets. (A) The 1.5-μm polystyrene beads coated with FITC-IgG were added to platelets for 30 min at 4°C in the absence (left) or presence (right) of 5 μg/ml anti-FcγRIIA monoclonal antibody IV.3. The platelets were then labeled with anti-CD42b-APC, and CD42⁺ events were measured for the presence of FITC-labeled beads. (B) Platelets incubated with 0.5- or 1.5-μm polystyrene beads coated with BSA or IgG. In some samples, 5 μg/ml anti-FcγRIIA MAb or an isotype-matched control IgG (5 μg/ml) was added to inhibit interaction. Data are means ± standard deviations (SD) representative of one experiment performed in triplicate. Experiments were repeated on 3 different days with platelets from three healthy volunteers with similar results.