title: Instability of Foxp3 expression limits the ability of induced regulatory T cells to mitigate graft versus host disease.
abstract: OBJECTIVE
  Graft versus host disease (GVHD) is the major complication of allogeneic bone marrow transplantation (BMT) and limits the therapeutic efficacy of this modality. Although the role of natural T-regulatory cells (nTreg) in attenuating GVHD has been extensively examined, the ability of induced T-regulatory cells (iTreg) to mitigate GVHD is unknown. The purpose of this study was to examine the ability of in vitro and in vivo iTregs to abrogate GVHD.
  
  
  METHODS
  We examined the ability of in vitro differentiated and in vivo iTregs to reduce the severity of GVHD in a clinically relevant mouse model of BMT. The effect of blockade of interleukin (IL) 6 signaling on the efficacy of these Treg populations was also studied.
  
  
  RESULTS
  In vitro differentiated iTregs fail to protect mice from lethal GVHD even when administered at high Treg:effector T-cell ratios. Lack of GVHD protection was associated with loss of Foxp3 expression and in vivo reversion of these cells to a proinflammatory phenotype characterized by secretion of IFN-γ. Phenotypic reversion could not be abrogated by blockade of IL-6 signaling or by in vitro exposure of iTregs to all-trans retinoic acid. In contrast, the in vivo induction of iTregs was significantly augmented by IL-6 blockade and this resulted in reduced GVHD.
  
  
  CONCLUSIONS
  Instability of Foxp3 expression limits the utility of adoptively transferred iTregs as a source of cellular therapy for the abrogation of GVHD. Blockade of IL-6 signaling augments the ability of in vivo iTregs to prevent GVHD but has no effect on in vitro differentiated iTregs.
authors.affiliation: Bone Marrow Transplant Program and the Departments of Microbiology, Pathology, and Medicine, Medical College of Wisconsin, Milwaukee, Wisconsin, USA.
authors.forename: Amy
authors.initials: A
authors.lastname: Beres
authors.forename: Richard
authors.initials: R
authors.lastname: Komorowski
authors.forename: Masahiko
authors.initials: M
authors.lastname: Mihara
authors.forename: William R
authors.initials: WR
authors.lastname: Drobyski
mesh_terms: D000818:Animals; D019138:Antibodies, Blocking / Q000276:immunology / Q000494:pharmacology; D016026:Bone Marrow Transplantation / Q000009:adverse effects; D051858:Forkhead Transcription Factors / Q000235:genetics / Q000378:metabolism*; D005786:Gene Expression Regulation / Q000276:immunology; D006086:Graft vs Host Disease / Q000209:etiology / Q000235:genetics / Q000276:immunology* / Q000503:physiopathology; D007155:Immunologic Factors / Q000276:immunology / Q000494:pharmacology; D007249:Inflammation / Q000276:immunology; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D010641:Phenotype; D019947:Receptors, Interleukin-6 / Q000037:antagonists & inhibitors / Q000276:immunology; D015398:Signal Transduction / Q000187:drug effects / Q000276:immunology; D050378:T-Lymphocytes, Regulatory / Q000187:drug effects / Q000276:immunology*; D014212:Tretinoin / Q000276:immunology
chemical_list: D019138:Antibodies, Blocking; D051858:Forkhead Transcription Factors; C498833:Foxp3 protein, mouse; D007155:Immunologic Factors; D019947:Receptors, Interleukin-6; D014212:Tretinoin