Characterization of donor and recipient CD8+ tissue-resident memory T cells in transplant nephrectomies.

Tissue-resident memory T (T) cells are characterized by their surface expression of CD69 and can be subdivided in CD103+ and CD103- T cells. The origin and functional characteristics of T cells in the renal allograft are largely unknown. To determine these features we studied T cells in transplant nephrectomies. T cells with a CD103+ and CD103- phenotype were present in all samples (n = 13) and were mainly CD8+ T cells. Of note, donor-derived T cells were only detectable in renal allografts that failed in the first month after transplantation. Grafts, which failed later, mainly contained recipient derived T cells. The gene expression profiles of the recipient derived CD8+ T cells were studied in more detail and showed a previously described signature of tissue residence within both CD103+ and CD103- T cells. All CD8+ T cells had strong effector abilities through the production of IFNγ and TNFα, and harboured high levels of intracellular granzyme B and low levels of perforin. In conclusion, our results demonstrate that donor and recipient T cells reside in the rejected renal allograft. Over time, the donor-derived T cells are replaced by recipient T cells which have features that enables these cells to aggressively respond to the allograft.