Implications of Resident Memory T Cells for Transplantation

Recent studies have established resident memory T cells (T-RM) as the dominant memory lymphocyte population surveying most nonlymphoid tissues. Unlike other memory T cell lineages, T-RM do not recirculate through blood and are permanently confined to their tissue of residence. T-RM orchestrate local immune responses and have been shown to accelerate local pathogen control in many experimental infection models. Here we briefly summarize recent advances in T-RM differentiation, maintenance, and their protective function. While little is known, we have speculated on the potential implications of T-RM for transplantation biology. Areas of emphasis include the role of passenger T-RM in controlling latent viral recrudescence in donor organs, donor T-RM as a source of graft-versus-host disease, the ability of T-RM to potently induce inflammation through sensing and alarm functions, and differentiation of host T cells into T-RM in response to local cues inside the allograft. Further investigation of T-RM in the context of transplantation might identify therapeutic targets to prolong graft survival. This review discusses the phenotype, function, and potential relevance for transplantation of resident memory T cells.