Editorial: Regulatory T Cells

Regulatory T cells (Tregs) are a subset of CD4 + T cells that maintain tolerance to self-antigens, prevent autoimmune disease, and limit anti-tumor immunity.Over recent years, Tregs have demonstrated great potential as either a target or immunotherapy in a variety of diseases, such as autoimmunity, cancer, transplantation and graft-versus-host disease (GVHD).In clinical trials, Tregs have been infused as an adoptive cellular therapy in diabetes, GVHD and organ transplantation.For example, in Nanjing Medical University in China, Dr. Ling Lu and his team have infused exvivo expanded nTregs to liver transplant recipients in combination with a reduction in immunosuppression to promote immune tolerance.As of writing, 5 patients out of 17 have ceased immunosuppression with the majority of the remaining patients receiving a reduced dose.Some other trials are also ongoing, both in GVHD and transplantation, including the Phase IIb TWO Study in Oxford.However, some challenges must be overcome before the implementation and widespread use of Treg therapy.This Research Topic describes the latest advances in the basic science and clinical application of Tregs, including insights into the use of Tregs for the treatment of tumors and autoimmune diseases, and new strategies for Treg therapy in organ transplantation.The phenotypic and functional diversity of Tregs has important implications for their biology and function.Tregs can mirror conventional T cell subsets, and include naïve, effector, and memory subpopulations.Here, Sjaastad et al. from the University of Minnesota focus on the ontogeny, phenotype and function of different effector Treg subsets, which is important for the future development of tools for specific subgroups and their functions.Tissue Tregs, also known as tissue-resident Tregs, do not recirculate in the blood or lymphatics and are adapted to the specific tissue environment.In this Research Topic Shao et al. review the phenotype, function, and cytokine expression of these Tissue Tregs.In local tissues, Tregs can restrain immune responses, maintain tissue homeostasis, and promote tissue recovery.With the increasing number of chronic tissue inflammatory diseases and immune deficiency diseases, understanding the role that Tregs play in either the control or perpetuation of these pathologies is crucial.Current studies suggest that Tregs may be a potential treatment for ischemia-reperfusion injury (IRI).Butyric acid (BA) is a product formed by intestinal microorganisms after decomposing indigestible food and is a potential negative immunomodulator.Chen et al. show that the heme oxygenase 1(HO-1)/STAT3 signaling pathway is related to the inhibitory effect of BA on the differentiation of Th17 cells.BA regulates the differentiation of Th17 cells into Tregs and reduces renal IRI.This provides a route for BA to inhibit inflammation by regulating the balance of Tregs to Th17 cells.Human amniotic mesenchymal stem cells (hAMSCs) have the potential for multi-directional differentiation and the ability to promote immune regulation and tissue repair in a number of diseases.Heren, Deng et al. provide convincing evidence for the hAMSC and Treg combined activity.The authors find that Tregs improve the function of hAMSCs by regulating the TGF-β/IDO signaling