Regulatory T cells as therapeutic cells

Purpose of review Although a plethora of data indicate the importance of regulatory T cells (Tregs) in experimental and clinical transplantation, are we any closer to seeing these cells as therapeutic tools in the clinic? This review discusses the functional and practical aspects of using CD4(+)CD25(hi)Foxp3(+) Tregs as cellular therapeutic products in clinical transplantation, focusing on the requirements in terms of phenotype, antigen specificity and preparation of Tregs. Recent findings Following the emergence of new phenotypic markers of Tregs as well as improved isolation methods, a few milestone clinical trials employing the adoptive transfer of Tregs are now underway. Although mounting data suggest that alloantigen-specific Tregs may provide higher therapeutic benefits in solid organ transplantation compared with polyclonal Tregs, it seems that the specificty of Treg selected for use will need to be tailored to each clinical transplantation setting. In addition, recent findings imply that immunosuppressive regimes will also need to be reevaluated in order to complement this therapeutic strategy. Summary Although many key questions about Tregs remain, we are undoubtedly entering an exciting era of Treg research in clinical transplantation. As renewed efforts focus on translational medical research, it seems as though, whether ready or not, Tregs are finally crossing from bench to bedside.