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Background & Aims: T-regulatory (Treg) cells suppress the immune response to maintain homeostasis. There are 2 main subsets of Treg cells: FOXP3 (forkhead box protein 3)-positive Treg cells, which do not produce high levels of effector cytokines, and type 1 Treg (Tr1) cells, which are FOXP3-negative and secrete interleukin (IL) 10. IL10 is an anti-inflammatory cytokine, so Tr1 cells might be used in the treatment of inflammatory bowel diseases. We aimed to develop methods to isolate and expand human Tr1 cells and define their functions., Methods: We obtained blood and colon biopsy samples from patients with Crohn's disease or ulcerative colitis or healthy individuals (controls). CD4 + T cells were isolated from blood samples and stimulated with anti-CD3 and anti-CD28 beads, and Tr1 cells were purified by using an IL10 cytokine-capture assay and cell sorting. FOXP3-positive Treg cells were sorted as CD4 + CD25 high CD127 low cells from unstimulated cells. Tr1 and FOXP3-positive Treg cells were expanded, and phenotypes and gene expression profiles were compared. T cells in peripheral blood mononuclear cells from healthy donors were stimulated with anti-CD3 and anti-CD28 beads, and the suppressive abilities of Tr1 and FOXP3-positive Treg cells were measured. Human colon organoid cultures were established, cultured with supernatants from Tr1 or FOXP3-positive cells, and analyzed by immunofluorescence and flow cytometry. T84 cells (human colon adenocarcinoma epithelial cells) were incubated with supernatants from Tr1 or FOXP3-positive cells, and transepithelial electrical resistance was measured to determine epithelial cell barrier function., Results: Phenotypes of Tr1 cells isolated from control individuals vs patients with Crohn's disease or ulcerative colitis did not differ significantly after expansion. Tr1 cells and FOXP3-positive Treg cells suppressed proliferation of effector T cells, but only Tr1 cells suppressed secretion of IL1B and tumor necrosis factor from myeloid cells. Tr1 cells, but not FOXP3-positive Treg cells, isolated from healthy individuals and patients with Crohn's disease or ulcerative colitis secreted IL22, which promoted barrier function of human intestinal epithelial cells. Tr1 cell culture supernatants promoted differentiation of mucin-producing goblet cells in intestinal organoid cultures., Conclusions: Human Tr1 cells suppress proliferation of effector T cells (adaptive immune response) and production of IL1B and TNF by myeloid cells (inmate immune response). They also secrete IL22 to promote barrier function. They might be developed as a cell-based therapy for intestinal inflammatory disorders., (Copyright © 2019 AGA Institute. Published by Elsevier Inc. All rights reserved.)

The two best-characterized types of CD4(+) regulatory T cells (Tregs) are Foxp3(+) Tregs and Foxp3(-) type 1 regulatory (Tr1) cells. The ability of Foxp3(+) Tregs and Tr1 cells to suppress adaptive immune responses is well known, but how these cells regulate innate immunity is less defined. We discovered that CD44(hi)Foxp3(-) T cells from unmanipulated mice are enriched in Tr1 cell precursors, enabling differentiation of cells that express IL-10, as well as Tr1-associated cell surface markers, CD49b and LAG-3, and transcription factors, cMaf, Blimp-1, and AhR. We compared the ability of Tr1 cells versus Foxp3(+) Tregs to suppress IL-1β production from macrophages following LPS and ATP stimulation. Surprisingly, Tr1 cells, but not Foxp3(+) Tregs, inhibited the transcription of pro-IL-1β mRNA, inflammasome-mediated activation of caspase-1, and secretion of mature IL-1β. Consistent with the role for IL-10 in Tr1 cell-mediated suppression, inhibition of inflammasome activation and IL-1β secretion was abrogated in IL-10R-deficient macrophages. Moreover, IL-1β production from macrophages derived from Nlrp3(A350V) knockin mice, which carry a mutation found in cryopyrin-associated periodic syndrome patients, was suppressed by Tr1 cells but not Foxp3(+) Tregs. Using an adoptive transfer model, we found a direct correlation between Tr1 cell engraftment and protection from weight loss in mice expressing a gain-of-function NLRP3. Collectively, these data provide the first evidence for a differential role of Tr1 cells and Foxp3(+) Tregs in regulating innate immune responses. Through their capacity to produce high amounts of IL-10, Tr1 cells may have unique therapeutic effects in disease-associated inflammasome activation., (Copyright © 2015 by The American Association of Immunologists, Inc.)

Chronic inflammation is known to promote metabolic dysregulation in obesity and type 2 diabetes. Although the precise origin of the unchecked inflammatory response in obesity is unclear, it is known that overproduction of proinflammatory cytokines by innate immune cells affects metabolism. For example, TNF-α contributes to the inability of cells to respond to insulin and to the increase in levels of insulin. Whether this hyperinsulinemia itself is part of a feedback loop that affects the progression of chronic adipose inflammation is unknown. In this article, we show that regulatory T cells (Tregs) express the insulin receptor, and that high levels of insulin impair the ability of Tregs to suppress inflammatory responses via effects on the AKT/mTOR signaling pathway. Insulin activated AKT signaling in Tregs, leading to inhibition of both IL-10 production and the ability of Tregs to suppress the production of TNF-α by macrophages in a contact-independent manner. The effect of insulin on Treg suppression was limited to IL-10 production and it did not alter the expression of other proteins associated with Treg function, including CTLA-4, CD39, and TGF-β. In a model of diet-induced obesity, Tregs from the visceral adipose tissue of hyperinsulinemic, obese mice showed a similar specific decrease in IL-10 production, as well as a parallel increase in production of IFN-γ. These data suggest that hyperinsulinemia may contribute to the development of obesity-associated inflammation via a previously unknown effect of insulin on the IL-10-mediated function of Tregs.

Interleukin-10 (IL-10)-secreting T regulatory type 1 (Tr1) cells are defined by their specific cytokine production profile, which includes the secretion of high levels of IL-10 and transforming growth factor-beta(TGF-beta), and by their ability to suppress antigen-specific effector T-cell responses via a cytokine-dependent mechanism. In contrast to the naturally occurring CD4+ CD25+ T regulatory cells (Tregs) that emerge directly from the thymus, Tr1 cells are induced by antigen stimulation via an IL-10-dependent process in vitro and in vivo. Specialized IL-10-producing dendritic cells, such as those in an immature state or those modulated by tolerogenic stimuli, play a key role in this process. We propose to use the term Tr1 cells for all IL-10-producing T-cell populations that are induced by IL-10 and have regulatory activity. The full biological characterization of Tr1 cells has been hampered by the difficulty in generating these cells in vitro and by the lack of specific marker molecules. However, it is clear that Tr1 cells play a key role in regulating adaptive immune responses both in mice and in humans. Further work to delineate the specific molecular signature of Tr1 cells, to determine their relationship with CD4+ CD25+ Tregs, and to elucidate their respective role in maintaining peripheral tolerance is crucial to advance our knowledge on this Treg subset. Furthermore, results from clinical protocols using Tr1 cells to modulate immune responses in vivo in autoimmunity, transplantation, and chronic inflammatory diseases will undoubtedly prove the biological relevance of these cells in immunotolerance.

Dendritic cells (DCs) are specialized antigen-presenting cells that monitor the antigenic environment and activate naive T cells. The role of DCs is not only to sense danger but also to tolerize the immune system to antigens encountered in the absence of maturation/inflammatory stimuli. Indeed, if a naive T cell encounters its antigen on immature DCs (iDCs), it may differentiate into a T-regulatory (Tr) rather than a T-effector cell. However, little is known about the mechanisms by which iDCs differentiate Tr cells. We developed a standardized and highly reproducible protocol to differentiate Tr cells by repetitive exposure of naive peripheral blood CD4(+) T cells to allogeneic iDCs. The resultant Tr cells are phenotypically and functionally identical to type 1 Tr (Tr1) cells because their generation requires production of IL-10 by iDCs, and they suppress T-cell responses through an interleukin-10 (IL-10)- and a transforming growth factor beta (TGF-beta)-dependent mechanism. In addition, Tr1 cells induced by iDCs do not require the presence of CD4(+)CD25(+) Tr cells for their generation, nor do they express high constitutive levels of CD25 or the transcription factor FoxP3. Thus, iDCs can drive the differentiation of Tr1 cells and can be used to generate large numbers of alloantigen-specific Tr1 cells for clinical use as a cellular therapy to restore peripheral tolerance.

Suppression by T regulatory (Tr) cells is essential for the induction of peripheral tolerance. Many types of CD4+ Tr cells have been described in a number of systems, and although the precise mechanisms which mediate their effects remain to be defined, it is well established that they can suppress immune responses via cell-cell interactions and/or the production of interleukin-10 (IL-10) and transforming growth factor-beta (TGF-beta). Type 1 T regulatory (Tr1) cells are defined by their ability to produce high levels of IL-10 and TGF-beta, and these cytokines mediate their ability to suppress pathological immune responses in the settings of transplantation, allergy and autoimmune disease. Tr1 cell activity is not necessarily beneficial, and they can also suppress immune responses to antigens from tumours and pathogens. In vivo, the differentiation of Tr1 cells is likely controlled by certain dendritic cells which promote IL-10 production and may express tolerogenic costimulatory molecules. Another subset of CD4+ Tr cells is defined by constitutive expression of CD25, and although these CD4+CD25+ Tr cells appear to suppress via mechanisms which are largely independent of cytokines, they may actively promote the differentiation of Tr1 cells. Many questions about the basic biology of Tr1 cells remain to be answered, but the development of therapeutic strategies designed to harness their immunoregulatory effects can already be contemplated., (Copyright 2002 S. Karger AG, Basel)

T regulatory (Tr) cells are essential for the induction of peripheral tolerance. Several types of Tr cells exist, including CD4(+) T cells which express CD25 constitutively and suppress immune responses via direct cell-to-cell interactions, and type 1 T regulatory (Tr1) cells, which function via secretion of interleukin (IL)-10 and transforming growth factor (TGF)-beta. The relationship between CD25(+)CD4(+) T cells and Tr1 cells remains unclear. Here, we demonstrate at the clonal level that Tr1 and CD25(+)CD4(+) T cells are two distinct subsets of regulatory cells with different cytokine production profiles. Furthermore, CD25(-)CD4(+) T cells can be rendered anergic by IL-10 and differentiated into Tr1 cells in the absence of CD25(+)CD4(+) T cells. Cloned human CD25(+)CD4(+) T cell populations are heterogeneous and only a subset of clones continues to express high levels of CD25 and is suppressive. The intensity of CD25, cytotoxic T lymphocyte antigen (CTLA)-4, and glucocorticoid-induced tumor necrosis factor (TNF) receptor expression correlates with the suppressive capacity of the T cell clones. None of the CD25(+)CD4(+) T cell clones with suppressive function produce IL-10, but all produce TGF-beta. Suppression mediated by CD25(+)CD4(+) T cell clones is partially dependent on TGF-beta, but not on constitutive high expression of CD25. Together these data indicate that naturally occurring human CD25(+)CD4(+) T cells are distinct from IL-10-producing Tr1 cells.

T regulatory (Treg) cells are critical for maintaining immune homeostasis and establishing tolerance to foreign, non-pathogenic antigens including those found in commensal bacteria and food. Because of their multiple suppressive mechanisms, Tregs represent a promising strategy for engineering tolerance to self and non-self antigens in chronic inflammatory diseases. Already in clinical trials in the transplantation setting, the question remains whether this therapy would be effective for the treatment of mucosal inflammatory diseases that do not pose an immediate threat to life. In this review we will discuss evidence from both animal models and patients suggesting that Treg therapy would be beneficial in the context of inflammatory bowel disease (IBD). We will examine the role of T-cell versus Treg dysfunction in IBD and discuss the putative antigens that could be potential targets of antigen-directed Treg therapy. Finally, the challenges of using Treg therapy in IBD will be discussed, with a specific emphasis on the role that the microbiota may play in the outcome of this treatment. As Treg therapy becomes a bedside reality in the field of transplantation, there is great hope that it will soon also be deployed in the setting of IBD and ultimately prove more effective than the current non-specific immunosuppressive therapies. [ABSTRACT FROM AUTHOR]

T-regulatory cells (Tregs) have a fundamental role in the establishment and maintenance of peripheral tolerance. There is now compelling evidence that deficits in the numbers and/or function of different types of Tregs can lead to autoimmunity, allergy, and graft rejection, whereas an over-abundance of Tregs can inhibit anti-tumor and anti-pathogen immunity. Experimental models in mice have demonstrated that manipulating the numbers and/or function of Tregs can decrease pathology in a wide range of contexts, including transplantation, autoimmunity, and cancer, and it is widely assumed that similar approaches will be possible in humans. Research into how Tregs can be manipulated therapeutically in humans is most advanced for two main types of CD4+ Tregs: forkhead box protein 3 (FOXP3)+ Tregs and interleukin-10-producing type 1 Tregs (Tr1 cells). The aim of this review is to highlight current information on the characteristics of human FOXP3+ Tregs and Tr1 cells that make them an attractive therapeutic target. We discuss the progress and limitations that must be overcome to develop methods to enhance Tregs in vivo, expand or induce them in vitro for adoptive transfer, and/or inhibit their function in vivo. Although many technical and theoretical challenges remain, the next decade will see the first clinical trials testing whether Treg-based therapies are effective in humans. [ABSTRACT FROM AUTHOR]

Suppression by T regulatory (Tr) cells is essential for induction of tolerance. Many types of Tr cells have been described in a number of systems, and their biology have been described in a number of systems, and their biology has been the subject of intensive investigation. Although many aspects of the mechanism by which these cells exert their effects remain to be elucidated, it is well established that Tr cells suppress immune responses via cell-to-cell interactions and/or the production of interleukin (IL)-10 and transforming growth factor (TGF)-Β. Type-1 T regulatory (Tr1) cells are defined by their ability to produce high levels of IL-10 and TGF-Β. Tr1 cells specific for a variety of antigens arise in vivo, but may also differentiate from naive CD4[sup+] T cells in the presence of IL-10 in vitro. Tr1 cells have a low proliferative capacity, which can be overcome by IL-15. Tr1 cells suppress naive and memory T helper type 1 or 2 responses via production of IL-10 and TGF-Β. Further characterization of Tr1 cells at the molecular level will define their mechanisms of action and clarify their relationship with other subsets of Tr cells. The use of TR1 cells to identify novel targets for the development of new therapeutic agents, and as a cellular therapy to modulate peripheral tolerance, can be foreseen. [ABSTRACT FROM AUTHOR]