title: Memory T cells and their exhaustive differentiation in allograft tolerance and rejection.
abstract: OBJECTIVE
  Memory T cells have emerged as a major threat to transplant survival; they are well equipped and well positioned to respond to antigens in an accelerated fashion. They participate in transplant rejection and resist interventions that usually contain naïve T cells. Thus, the means to prevent memory T cells from attacking allotransplants are an important issue in transplantation.
  
  
  RESULTS
  Recent studies in other models suggest that effector T cells, which include both freshly activated T cells and memory T cells, can acquire 'an exhausted phenotype' in that they progressively lose their effector activities. This response is highly regulated, antigen specific, and driven primarily by antigen persistence. This exhausted phenotype has not been carefully explored in transplant models, and its role in transplant survival remains largely unknown.
  
  
  CONCLUSIONS
  Studies of T-cell exhaustion may reveal additional facets of the fundamental mechanisms of transplant survival. T-cell exhaustion may be an alternative way of preventing memory development. Future studies are needed to further improve our understanding of T-cell exhaustion in transplantation.
authors.affiliation: Department of Immunology, Lerner Research Institute, The Cleveland Clinic Foundation, Cleveland, Ohio.
authors.forename: Anna
authors.initials: A
authors.lastname: Valujskikh
authors.forename: Xian C
authors.initials: XC
authors.lastname: Li
mesh_terms: D000818:Animals; D002454:Cell Differentiation; D006084:Graft Rejection / Q000276:immunology*; D006085:Graft Survival / Q000276:immunology; D006801:Humans; D007156:Immunologic Memory; D013601:T-Lymphocytes / Q000276:immunology*; D023001:Transplantation Tolerance / Q000276:immunology*; D014184:Transplantation, Homologous / Q000276:immunology*