FIGURE 2.

Functional platelet activation and aggregation testing. Patient serum activates and aggregates donor platelets in functional tests. Expression of P‐selectin on donor test platelets (pooled platelets from two donors) was measured by flow cytometry (anti‐CD62P mAb, PE) after incubation with patient serum both under buffer conditions and with addition of PF4 (10 μg/ml). The FcɣRIIA‐blocking mAb IV.3 (10 μg/ml) efficiently inhibited the activation. Pooled serum from four healthy donors served as negative control, and TRAP stimulation of donor test platelets was used as positive control (A). Aggregation of donor test platelets was measured by whole‐blood impedance aggregometry in heparin‐induced multiple electrode aggregometry, in presence of low or high heparin concentrations and in the absence of added heparin (saline). The red and blue lines represent duplicate measurements. AU denotes arbitrary units, and the area under the curve (B)