CD4+ CD25+ regulatory T cells approach the clinic

TGF-β1-induced regulatory T cells

Besides central tolerance peripheral tolerance is an important mechanism to avoid development of autoimmunity. Naturally occurring thymic-derived regulatory T cells (nTreg) mediate peripheral tolerance by suppressing autoreactive T cells clones having escaped thymic deletional control. This implies that nTreg have therapeutic potential to dampen autoimmune disease. However, one of the main challenges for the therapeutic application of nTreg still remains the scarce amount of nTreg available. Transforming growth factor beta (TGF-β1) plays a critical role in the generation and immunosuppressive function of nTreg thereby contributing to immune homeostasis. TGF-β1 is thought to be essential for the generation and function of nTreg and regulatory T cells with suppressive properties can be induced in vitro by TGF-β1. These so-called TGF-β1-induced regulatory T cells (iTreg) can be induced in vitro from conventional CD4(+) T cells by addition of TGF-β1 and this discovery has added new options to use regulatory T cells therapeutically. Here we discuss the generation and in vitro and in vivo functions of murine and human TGF-β1-induced regulatory T cells in light of potential application as treatment for autoimmune diseases including current problems and drawbacks in their therapeutic use.

Characterization of murine non-adherent bone marrow cells leading to recovery of endogenous hematopoiesis

Non-adherent bone marrow-derived cells (NA-BMCs) are a mixed cell population that can give rise to multiple mesenchymal phenotypes and that facilitates hematopoietic recovery. We characterized NA-BMCs by flow cytometry, fibroblast colony-forming units (CFU-f), real-time PCR, and in in vivo experiments. In comparison to adherent cells, NA-BMCs expressed high levels of CD11b(+) and CD90(+) within the CD45(+) cell fraction. CFU-f were significantly declining over the cultivation period, but NA-BMCs were still able to form CFU-f after 5 days. Gene expression analysis of allogeneic NA-BMCs compared to bone marrow (BM) indicates that NA-BMCs contain stromal, mesenchymal, endothelial cells and monocytes, but less osteoid, lymphoid, and erythroid cells, and hematopoietic stem cells. Histopathological data and analysis of weight showed an excellent recovery and organ repair of lethally irradiated mice after NA-BMC transplantation with a normal composition of the BM.

Role of T cells in graft rejection and transplantation tolerance

Transplantation is the most effective treatment for end-stage organ failure, but organ survival is limited by immune rejection and the side effects of immunosuppressive regimens. T cells are central to the process of transplant rejection through allorecognition of foreign antigens leading to their activation, and the orchestration of an effector response that results in organ damage. Long-term transplant acceptance in the absence of immunosuppressive therapy remains the ultimate goal in the field of transplantation and many studies are exploring potential therapies. One promising cellular therapy is the use of regulatory T cells to induce a state of donor-specific tolerance to the transplant. This article first discusses the role of T cells in transplant rejection, with a focus on the mechanisms of allorecognition and the alloresponse. This is followed by a detailed review of the current progress in the field of regulatory T-cell therapy in transplantation and the translation of this therapy to the clinical setting.

Therapeutic potential of FOXP3(+) regulatory T cells and their interactions with dendritic cells

FOXP3(+) regulatory T cells, a unique subset of T cells, are critical for orchestrating an immune response and preventing self-reactivity. With the increasing prevalence and unsatisfactory treatment of autoimmunity, allergic diseases, cancer and chronic infections, much attention has been focused on understanding their mechanisms of action in order to manipulate their function. One goal is to develop drugs or biologics that can enhance or abrogate their functions. Another approach is to utilize Tregs in adoptive cell-based therapy to treat autoimmune diseases or transplant-related complications. This review will focus on their therapeutic potential and mechanisms of action, particularly their interaction with dendritic cells.