CD155 on Human Vascular Endothelial Cells Attenuates the Acquisition of Effector Functions in CD8 T Cells

Objective—CD155 is a cell surface protein that has recently been described to exert immune regulatory functions. We have characterized the expression of CD155 on human vascular endothelial cells (ECs) and examined its role in the regulation of T-cell activation. Methods and Results—CD155 was expressed on resting human vascular ECs and was upregulated in an interferon-γ (IFNγ)–dependent manner. When the function of CD155 in regulating T-cell activation was examined, antibody-mediated neutralization of CD155 did not affect CD8 T-cell proliferation in response to stimulation with ECs. However, neutralization of CD155 activity or small interfering RNA-mediated inhibition of CD155 expression in ECs increased expression of IFNγ and cytotoxic effector function in activated CD8 T cells. Conclusion—CD155 is an IFNγ-inducible immune regulatory protein on the surface of human ECs that attenuates the acquisition of effector functions in CD8 T cells.