hPF4-VWF-HIT antibody complexes are prothrombotic in vitro. (A) Representative fields showing (top) uninjured and (bottom) injured endothelium as in Figure 1B, but after exposure to the flow of recalcified whole human blood for 10 minutes. Binding of platelets to the VWF strings is shown. The bottom channel shows an injured area with platelets and the immediate, contiguous uninjured downstream area resembling in appearance the uninjured top channel. (B) Same as in panel A, but with the inclusion of hPF4 (25 µg/mL) and the indicated monoclonal antibody (10 µg/mL) and studied at the time points indicated. Representative binding of labeled KKO and platelets are shown. Platelet accumulation at 10 and 40 minutes is shown. (C) Same as in panel B, but for N ≥ 5 separate studies. Means ± 1 SEM are shown. P values were determined using a 1-way ANOVA.