DnIκB expression in human umbilical vein endothelial cells (HUVECs) affects cellular responsiveness to tumor necrosis factor (TNF)-α activation, leading to diminished expression of intercellular adhesion molecule-1 protein as determined by flow cytometry. HUVECs were infected with AddnIκB (7,500 vp/cell) or AdLacZ (7,500 vp/cell). After 24 hours of culturing, cells were activated with 100 ng/ml TNF-α, or left resting. Cells were detached 4 hours after activation and subjected to flow cytometric analysis. Non-activated, resting HUVECs (solid line with gray area); TNF-α activated HUVECs (bold solid line); TNF-α activated HUVECs infected with AddnIκB (solid line); and TNF-α activated HUVECs infected with AdLacZ control virus (dotted line). FITC, fluoroscein isothiocyanate. MIF, mean fluorescence intensity.