Plasticity of intragraft alloreactive T cell clones in human gut correlates with transplant outcomes

The site of transition between tissue resident memory (TRM) and circulating phenotypes of T cells is unknown. We integrated clonotype, alloreactivity and gene expression profiles of graft-repopulating recipient T cells in the intestinal mucosa at the single cell level after human intestinal transplantation. Host-versus-graft (HvG)-reactive T cells mainly distributed to TRM, Teff/TRM and T follicular helper compartments. RNA velocity analysis demonstrated a trajectory from TRM to effector T (Teff)/TRM clusters in association with rejection. By integrating pre- and post-Tx mixed lymphocyte reaction-determined alloreactive repertoires, we observed that pre-existing HvG-reactive T cells that demonstrated tolerance in the circulation were dominated by TRM profiles in quiescent allografts. Putative de novo HvG-reactive clones showed a transcriptional profile skewed to cytotoxic effectors in rejecting grafts. Inferred protein regulon network analysis revealed upstream regulators that accounted for the effector and tolerant T cell states. We demonstrate Teff/TRM interchangeability for individual T cell clones with known (allo)recognition in human gut, providing novel insight into TRM biology.