Fig. 3.

A-C. Spontaneous (A, C) and collagen-induced healthy donor platelet aggregation (B, C) triggered by the acute phase plasma from patient 1. (A) Spiking with patient EDTA-plasma: spontaneous aggregation (no agonist) of platelets from healthy donor (duplicate). Glycoprotein (GP) IIb/IIIa inhibitor (eptifibatide) (2 μg/mL) abolished the spontaneous aggregation, as did intravenous immunoglobin (IVIG) (5 mg/mL). (B) Spiking with control plasma: spontaneous aggregation (no agonist) did not occur. Collagen-induced aggregation supplemented with platelet factor 4 (PF4, 4 μg/mL) was not enhanced. (C) Spiking with patient plasma: immediate spontaneous aggregation in platelets spiked with patient plasma occurred, and continued upon adding collagen. Addition of PF4 enhanced collagen-induced aggregation. GPIIb/IIIa inhibitor and IVIG at 10 mg/mL both inhibited collagen-induced aggregation, but IVIG at 5 mg/mL had only a moderate response with control (B) or patient plasma (C). PF4 did not counteract the inhibitory effect of GPIIb/IIIa inhibitor or IVIG (10 mg/mL) in control (B) or patient plasma (C).