Effect of exposing HUVECs to flow on their up-regulation of surface expression of E-selectin in response to treatment with TNF. HUVECs were cultured under static conditions or exposed to shear stress of 0.3 Pa or 2.0 Pa for 28 hours, with 100 U/mL TNF added for the last 4 hours. Data are mean ± SEM from 3 experiments using immunofluorescence labeling and flow cytometry. Values are expressed relative to intensity of fluorescence for HUVECs labeled with nonspecific control antibody. *P < .05 compared with HUVECs treated with TNF under static conditions. Horizontal line represents relative fluorescence intensity (set at 1).