Memory T cells in transplantation - Progress and challenges

Purpose of Review: Memory T cells present a different set of challenges to transplant patients; they are needed for protection against invading pathogens, especially under conditions of immunosuppression. But their presence also threatens transplant survival, as some of them are alloreactive. Efforts to resolve this paradox will be critical in the induction of transplant tolerance. Recent Findings: There has been significant progress made in the past few years in the areas of population diversity of memory T cells, metabolic control of their induction, and mechanisms and pathways involved in memory cell exhaustion. Multiple targets on memory T cells have been identified, some of which are under vigorous testing in various transplant models. Summary: Memory T cells are both friends and foes to transplant patients, and tolerance strategies should selectively target alloreactive memory T cells and leave other memory cells unaltered. This situation remains a major challenge in the clinic.