Figure 2: Human Platelet Accrual on Plasma VWF

<b>(A)</b> Main chain schematic of the human von Willebrand factor (VWF)-A1 domain depicting residues that differ from its murine counterpart. <b>Colored spheres</b> denote the following: <b>black</b> are residues with buried side chains, <b>green</b> have partially buried side chains, <b>red</b> have exposed side chains on the front and upper surfaces, and <b>gold</b> have exposed side chains on the lower and back surfaces. <b>Circled in blue</b> is residue 1326, which plays a key role in permitting interactions with the GPIbα on human and mouse platelets (29). Accumulation of platelets on <b>(B)</b> surface-immobilized human plasma VWF or <b>(C)</b> murine plasma VWF^HA1 is shown. Citrated whole blood from neonatal patients or healthy adults was perfused over the reactive substrate for 3 min (wall shear rate of 1,600 s⁻¹) before assessing the number of interacting platelets. <b>(D)</b> Percentage of translocating platelets that became firmly adherent in response to infusion of buffer containing adenosine diphosphate (20 μM). The human GPIbα function blocking monoclonal antibody (mAb) 6D1 (10 μg/ml) or the αIIbβ3 inhibitor abciximab (10 μg/ml) was added to blood 10 min before use. See Supplemental Video 1. Data represent the mean ± SEM (n = 10 individuals per age group). ***p &lt; 0.001 for antibody treatment versus no treatment according to Mann-Whitney <i>U</i> test. CHD = congenital heart disease.