Regulatory T cells: hypes and limitations.
OBJECTIVE
In recent years there has been increased interest in understanding the physiology and function of regulatory T cells. In this review we focus on the characterization of regulatory T-cell subsets and their potential therapeutic use in organ transplantation.


RESULTS
Regulatory T cells can play an instrumental role in the establishment of operational tolerance to allografts. The level of expression and the extent of posttranslational acetylation of the regulatory T-cell specific transcription factor Foxp3 are important modulators of their suppressive activity. Low expression of CD127 can be used as a novel marker to define pure regulatory T-cell populations and the expression of CD45RA on CD4CD25 regulatory T cells characterizes a population with a more stable phenotype upon expansion in vitro. Interleukin-35 is a recently discovered immunosuppressive cytokine secreted by CD4CD25 regulatory T cells. Although the presence of allospecific memory T cells in the pretransplant period and the use of immunosuppressants might interfere with the effectiveness of regulatory T-cell-based therapies, encouraging results indicate that the immunosuppressive drug rapamycin does not affect the expansion and function of regulatory T cells and could be included in a combined therapy.


CONCLUSIONS
Important advances have been made towards establishing regulatory T cells as a viable therapy in transplantation and the first clinical trials using human regulatory T cells are currently underway. There are, however, important limitations and safety issues that have to be addressed before this therapy can be fully translated into the clinic.
Schiopu
Alexandru
A
Transplantation Research Immunology Group, Nuffield Department of Surgery, John Radcliffe Hospital, Oxford University, Headington, Oxford, United Kingdom.
Wood
Kathryn J
KJ
D019264:Adoptive Transfer; D000818:Animals; D006084:Graft Rejection / Q000276:immunology* / Q000517:prevention & control; D006085:Graft Survival / Q000187:drug effects; D006801:Humans; D007166:Immunosuppressive Agents / Q000627:therapeutic use; D016377:Organ Transplantation / Q000009:adverse effects*; D016176:T-Lymphocyte Subsets / Q000187:drug effects / Q000276:immunology* / Q000637:transplantation; D050378:T-Lymphocytes, Regulatory / Q000187:drug effects / Q000276:immunology* / Q000637:transplantation; D023001:Transplantation Tolerance; D014184:Transplantation, Homologous; D016896:Treatment Outcome
D007166:Immunosuppressive Agents