Effect of exposing HUVECs to flow on their response to different concentrations of TNF. Response was assessed by (A) number of adherent neutrophils, and (B) percentage of adherent neutrophils transmigrating through the monolayer. HUVECs were cultured static (□) or exposed to a shear stress of 0.3 Pa (▨) for 28 hours, with TNF added for the last 4 hours, followed by flow-based adhesion assay. Data are mean ± SEM from 3 or 4 experiments at each concentration of TNF. Analysis of variance (ANOVA) showed significant effect of culture conditions on adhesion (P < .05) and transmigration (P < .01). *P < .05, **P < .01 compared with results for static cultures by paired t test.