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.