Alloreactive T-cell memory is present in every transplant recipient and endangers graft
survival. Even in the absence of known sensitizing exposures, heterologous immunity and
homeostatic T-cell proliferation generate'endogenous' memory T cells with donorreactivity.
We have recently shown that endogenous donor-reactive CD8 memory T cells infiltrate
murine cardiac allografts within hours of reperfusion and amplify early posttransplant
inflammation by producing IFN-γ. Here, we have tested the role of ICOS costimulation in …