Regulatory T cells: prospective for clinical application in hematopoietic stem cell transplantation

Purpose of review Regulatory T cells exert a dominant effect in controlling autoimmunity and maintaining peripheral tolerance. Regulatory T cells are also involved in preventing allograft rejection and graft versus host disease. Cellular therapy with expanded regulatory T cells represents a promising approach to control T-cell mediated pathology. In this review we will summarize the efforts to design new methods for expanding regulatory T cells and exploit their regulatory function as cellular therapy for the treatment of graft versus host disease after hematopoietic stem cell transplantation. Recent findings Among CD4+ T cells, the best described are the naturally occurring CD4+CD25+ regulatory T cells and type 1 regulatory T cells. Recent progress has been made in the characterization of both subsets in terms of isolation and induction, respectively. However, a clear definition of their mechanisms of action has still to be achieved. Summary Better understanding of the mechanisms of suppression mediated by regulatory T cells might enable their use to modulate specific immune responses. Moreover, the recent development of methods allowing the ex-vivo expansion of regulatory T cells to provide sufficient number of cells for in vivo infusion, represents the first step toward the use of these cells as cellular therapy for the treatment of immunologic and hematological diseases.