High CMV-specific T-cell frequency is associated with more endothelial damage. Endothelial cells were activated by either high- or low-responder supernatants from CMV-seropositive donors with high or low T-cell frequencies to CMV antigen. PBMCs were then added to these differentially activated endothelial cultures and allowed to adhere overnight. Nonadherent cells were removed the next day. The resulting cocultures were monitored for endothelial damage over the course of 6 days. (A) Damage results to endothelial monolayer activated using coculture supernatants from a high-responder donor. (B) Results from endothelial monolayers activated by a low-responder donor. (C) Results from resting-state, nonactivated endothelial cells. For image information, see Document S1 (available on the Blood website; see the Supplemental Materials link at the top of the online article.