Neutrophil activation on VWF at 100 s⁻¹ is HNA-3a, calcium, and VWF A1-domain dependent and can be exacerbated by LPS challenge. (A) Representative images of HNA-3a or HNA-3b neutrophils (anti-Ly6G IgG) submitted to a 100 s⁻¹ shear rate in the absence or presence of calcium or preactivated with LPS prior to perfusion (5 or 25 µg/mL) (Cellix flow chambers, n = 3 donors per genotype). (B) Representative images of HNA-3a neutrophils perfused at a 100 s⁻¹ shear rate on immobilized BSA, fibrinogen, or VWF A1-Fc domain. Neutrophil Fc receptors were blocked with anti-CD32 antibody (Ab) for A1 domain experiments. Scale bars, 100 µm. Lines delimit flow channels and the well entrance (n = 3 donors per genotype).