Prior Viral Infection Primes Cross-Reactive CD8+ T cells that Respond to Mouse Heart Allografts

Significant evidence suggests a connection between transplant rejection and prior (or existing) infection. Indeed, high levels of pre-existing memory T cells correlate with subsequent rejection in humans. Further, viral infection can elicit viral-specific T cells that cross-react with allo-MHC capable of driving allograft rejection in mice. Despite these advances, and despite their critical role in transplant rejection, a systematic study of allograft resident T cells, their specificities, and the role of cross-reactivity with viral antigens has not been performed. Here, we established a model to identify, isolate, and characterize cross-reactive T cells using Nur77 reporter mice (C57BL/6 background), which transiently express GFP exclusively upon TCR engagement. We infected Nur77 mice with lymphocytic choriomeningitis virus (LCMV) to generate a robustmemory compartment, where quiescent LCMV-specific memory CD8+ T cells could be readily tracked with MHC tetramer staining. Then, we transplanted LCMV immune mice with allogeneic hearts and monitored expression of GFP within MHC-tetramer defined viral-sp. T cells as an indicator of their ability to cross-react with alloantigens.