Effect of exposing HUVECs to flow at different shear stresses on their response to TNF. Response was assessed by the number of adherent neutrophils. HUVECs were cultured static (□) or exposed to flow (▨) at a shear stress of 0.3, 1.0, or 2.0 Pa for 28 hours with 100 U/mL TNF added for the last 4 hours, followed by flow-based adhesion assay. Data are mean ± SEM from 3 to 5 experiments at each stress. ANOVA showed significant effect of the level of stress on adhesion (P < .01). *P < .02 compared with results for static cultures by paired t test.