KKO and HIT patient IgGs bind to PF4-VWF complexes ex vivo. (A) Representative injured area and downstream of injury region (DR) in the microfluidic channels as in Figure 1C stained for VWF and KKO. (B) Comparison as in Figure 1D for total KKO bound relative to the UUR and DR. Means ± 1 SEM are shown for N ≥ 5 separate studies. P values were determined by a 1-way ANOVA. Panels C-D are similar to panels A-B, respectively, but show only the injured areas stained for either VWF or for anti-human Fab fragments (αHm-Fab). (C) Diluted plasma from patients at high risk of having HIT or low-risk controls (Ctl)³³  were used. (D) Relative binding of IgG from the HIT or control samples (N = 6 normal controls) are shown. Means ± 1 SEM are shown from N ≥ 5 separate studies. P values were determined using a 1-way ANOVA to compare relative binding of each IgG in the absence of hPF4 vs in the presence of infused PF4 (25 µg/mL) with control samples in the absence of PF4 set to 1.