HRS cell C/S-stimulated HUVECs show enhanced T-cell interactions under flow. Both (A) CD4⁺ CD45RA⁺ naïve T cells and (B) CD4⁺ CD45RO⁺ memory T cells bind to KM-H2 C/S-stimulated HUVECs in a shear stress-dependent manner (stripe bar). The respective numbers of interacting cells is comparable to that seen with TNF-α–stimulated HUVECs (dark gray bar). Very few T cells bind to unstimulated HUVECs (black bar). Neutralization of LTα in the C/S prior to use in stimulating HUVECs resulted in a significant reduction in the numbers of interacting (C) naïve and (D) memory T cells at the shear stress of 0.76 dynes/cm². The live time cell-cell interactions were video recorded using a CCD camera and VCR (SVT-N24P; Sony), and analysis was carried out offline. Values shown are mean ± SEM from 3-5 experiments. *P ≤ .05 compared with unstimulated HUVECs for A and B; and compared with C/S-stimulated controls for C and D.