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Summary: Since their discovery, CD4+CD25hiFOXP3hi regulatory T cells (Tregs) have been firmly established as a critical cell type for regulating immune homeostasis through a plethora of mechanisms. Due to their immunoregulatory power, delivery of polyclonal Tregs has been explored as a therapy to dampen inflammation in the settings of transplantation and autoimmunity. Evidence shows that Treg therapy is safe and well‐tolerated, but efficacy remains undefined and could be limited by poor persistence in vivo and lack of antigen specificity. With the advent of new genetic engineering tools, it is now possible to create bespoke "designer" Tregs that not only overcome possible limitations of polyclonal Tregs but also introduce new features. Here, we review the development of designer Tregs through the perspective of three 'eras': (1) the era of FOXP3 engineering, in which breakthroughs in the biological understanding of this transcription factor enabled the conversion of conventional T cells to Tregs; (2) the antigen‐specificity era, in which transgenic T‐cell receptors and chimeric antigen receptors were introduced to create more potent and directed Treg therapies; and (3) the current era, which is harnessing advanced genome‐editing techniques to introduce and refine existing and new engineering approaches. The year 2022 marked the entry of "designer" Tregs into the clinic, with exciting potential for application and efficacy in a wide variety of immune‐mediated diseases. [ABSTRACT FROM AUTHOR]

Regulatory T cells (Tregs) are essential for immune homeostasis and suppression of pathological autoimmunity but can also play a detrimental role in cancer progression via inhibition of anti‐tumor immunity. Thus, there is broad applicability for therapeutic Treg targeting, either to enhance function, for example, through adoptive cell therapy (ACT), or to inhibit function with small molecules or antibody‐mediated blockade. For both of these strategies, the metabolic state of Tregs is an important consideration since cellular metabolism is intricately linked to function. Mounting evidence has shown that targeting metabolic pathways can selectively promote or inhibit Treg function. This review aims to synthesize the current understanding of Treg metabolism and discuss emerging metabolic targeting strategies in the contexts of transplantation, autoimmunity, and cancer. We discuss approaches to gene editing and cell culture to manipulate Treg metabolism during ex vivo expansion for ACT, as well as in vivo nutritional and pharmacological interventions to modulate Treg metabolism in disease states. Overall, the intricate connection between metabolism and phenotype presents a powerful opportunity to therapeutically tune Treg function. [ABSTRACT FROM AUTHOR]

Activation‐induced marker (AIM) assays have proven to be an accessible and rapid means of antigen‐specific T‐cell detection. The method typically involves short‐term incubation of whole blood or peripheral blood mononuclear cells with antigens of interest, where autologous antigen‐presenting cells process and present peptides in complex with major histocompatibility complex (MHC) molecules. Recognition of peptide–MHC complexes by T‐cell receptors then induces upregulation of activation markers on the T cells that can be detected by flow cytometry. In this review, we highlight the most widely used activation markers for assays in the literature while identifying nuances and potential downfalls associated with the technique. We provide a summary of how AIM assays have been used in both discovery science and clinical studies, including studies of severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) immunity. This review primarily focuses on AIM assays using human blood or peripheral blood mononuclear cell samples, with some considerations noted for tissue‐derived T cells and nonhuman samples. AIM assays are a powerful tool that enables detailed analysis of antigen‐specific T‐cell frequency, phenotype and function without needing to know the precise antigenic peptides and their MHC restriction elements, enabling a wider analysis of immunity generated following infection and/or vaccination. [ABSTRACT FROM AUTHOR]

The metabolic milieu is emerging as a major contributing factor in the maintenance of the immunosuppressive microenvironment within tumors. In particular, the presence of lactic acid produced by highly glycolytic cancer cells is known to suppress antitumor immune cell subsets while promoting immunosuppressive cell populations, such as regulatory T cells (Tregs). Unlike conventional T cells, Tregs have a unique, potent ability to take up lactic acid to fuel both mitochondrial metabolism and gluconeogenesis, thus supporting suppressive function and proliferation. In this issue of the European Journal of Immunology [Eur. J. Immunol. 2023.53:2250258], Rao et al. uncover a novel mechanism by which lactic acid can support Treg accumulation within tumors in mice. This study shows that lactic acid, through a pH‐dependent mechanism rather than lactate itself, promotes TGFβ‐induced differentiation of Tregs from conventional CD4+ T cells. These findings build on the already multifaceted role of lactic acid in maintaining an immunosuppressive tumor microenvironment. [ABSTRACT FROM AUTHOR]

Regulatory T‐cell (Treg) therapy is under clinical investigation for the treatment of transplant rejection, autoimmune disease, and graft‐versus‐host disease. With the advent of genome editing, attention has turned to reinforcing Treg function for therapeutic benefit. A hallmark of Tregs is dampened activation of PI3K‐AKT signaling, of which PTEN is a major negative regulator. Loss‐of‐function studies of PTEN, however, have not conclusively shown a requirement for PTEN in upholding Treg function and stability. Using CRISPR‐based genome editing in human Tregs, we show that PTEN ablation does not cause a global defect in Treg function and stability; rather, it selectively blocks their ability to suppress antigen‐presenting cells. PTEN‐KO Tregs exhibit elevated glycolytic activity, upregulate FOXP3, maintain a Treg phenotype, and have no discernible defects in lineage stability. Functionally, PTEN is dispensable for human Treg‐mediated inhibition of T‐cell activity in vitro and in vivo but is required for suppression of costimulatory molecule expression by antigen‐presenting cells. These data are the first to define a role for a signaling pathway in controlling a subset of human Treg activity. Moreover, they point to the functional necessity of PTEN‐regulated PI3K‐AKT activity for optimal human Treg function. [ABSTRACT FROM AUTHOR]

Cytometric immunophenotyping is a powerful tool to discover and implement T‐cell biomarkers of type 1 diabetes (T1D) progression and response to clinical therapy. Although many discovery‐based T‐cell biomarkers have been described, to date, no such markers have been widely adopted in standard practice. The heterogeneous nature of T1D and lack of standardized assays and experimental design across studies is a major barrier to the broader adoption of T‐cell immunophenotyping assays. There is an unmet need to harmonize the design of immunophenotyping assays, including those that measure antigen‐agnostic cell populations, such that data collected from different clinical trial sites and T1D cohorts are comparable, yet account for cohort‐specific features and different drug mechanisms of action. In these Guidelines, we aim to provide expert advice on how to unify aspects of study design and practice. We provide recommendations for defining cohorts, method implementation, as well as tools for data analysis and reporting by highlighting and building on selected successes. Harmonization of cytometry‐based T‐cell assays will allow researchers to better integrate findings across trials, ultimately enabling the identification and validation of biomarkers of disease progression and treatment response in T1D. [ABSTRACT FROM AUTHOR]

Treg therapy holds promise as a potentially curative approach to establish immune tolerance in transplantation and autoimmune disease. An outstanding question is whether therapeutic Tregs have the potential to transdifferentiate into effector T‐cells and, thus, exacerbate rather than suppress immune responses. In mice, the transcription factor Helios is thought to promote Treg lineage stability in a range of inflammatory contexts. In humans, the role of Helios in Tregs is less clear, in part, due to the inability to enrich and study subsets of Helios‐positive versus Helios‐negative Tregs. Using an in vitro expansion system, we found that loss of high Helios expression and emergence of an intermediate Helios (Heliosmid)‐expressing population correlated with Treg destabilization. We used CRISPR/Cas9 to genetically ablate Helios expression in human naive or memory Tregs and found that Helios‐KO and unedited Tregs were equivalent in their suppressive function and stability in inflammation. Thus, high Helios expression is a marker, but not a driver, of human Treg stability in vitro. These data highlight the importance of monitoring Helios expression in therapeutic Treg manufacturing and provide new insight into the biological function of this transcription factor in human T‐cells. [ABSTRACT FROM AUTHOR]

Transforming growth factor‐beta (TGF‐β) family proteins mediate many vital biological functions in growth, development and regulation of the immune system. TGF‐β itself controls immune homeostasis and inflammation, including conversion of naïve CD4+ T cells into Foxp3+ regulatory T cells (Tregs) in the presence of interleukin‐2 and T‐cell receptor ligands. The helminth parasite Heligmosomoides polygyrus exploits this pathway through a structurally novel TGF‐β mimic (Hp‐TGM), which binds to mammalian TGF‐β receptors and induces Tregs. Here, we performed detailed comparisons of Hp‐TGM with mammalian TGF‐β. Compared with TGF‐β, Hp‐TGM induced greater numbers of Foxp3+ Tregs (iTregs), with more intense Foxp3 expression. Both ligands upregulated Treg functional markers CD73, CD103 and programmed death‐ligand 1, but Hp‐TGM induced significantly higher CD39 expression than did TGF‐β. Interestingly, in contrast to canonical TGF‐β signaling through Smad2/3, Hp‐TGM stimulation was slower and more sustained. Gene expression profiles induced by TGF‐β and Hp‐TGM were remarkably similar, and both types of iTregs suppressed T‐cell responses in vitro and experimental autoimmune encephalomyelitis‐driven inflammation in vivo. In vitro, both types of iTregs were equally stable under inflammatory conditions, but Hp‐TGM‐induced iTregs were more stable in vivo during dextran sodium sulfate‐induced colitis, with greater retention of Foxp3 expression and lower conversion to a ROR‐γt+ phenotype. Altogether, results from this study suggest that the parasite cytokine mimic, Hp‐TGM, may deliver a qualitatively different signal to CD4+ T cells with downstream consequences for the long‐term stability of iTregs. These data highlight the potential of Hp‐TGM as a new modulator of T‐cell responses in vitro and in vivo. [ABSTRACT FROM AUTHOR]

Immune homeostasis in the intestine is tightly controlled by FOXP3+ regulatory T cells (Tregs), defects of which are linked to the development of chronic conditions, such as inflammatory bowel disease (IBD). As a mechanism of immune evasion, several species of intestinal parasites boost Treg activity. The parasite Heligmosomoides polygyrus is known to secrete a molecule (Hp‐TGM) that mimics the ability of TGF‐β to induce FOXP3 expression in CD4+ T cells. The study aimed to investigate whether Hp‐TGM could induce human FOXP3+ Tregs as a potential therapeutic approach for inflammatory diseases. CD4+ T cells from healthy volunteers were expanded in the presence of Hp‐TGM or TGF‐β. Treg induction was measured by flow cytometric detection of FOXP3 and other Treg markers, such as CD25 and CTLA‐4. Epigenetic changes were detected using ChIP‐Seq and pyrosequencing of FOXP3. Treg phenotype stability was assessed following inflammatory cytokine challenge and Treg function was evaluated by cellular co‐culture suppression assays and cytometric bead arrays for secreted cytokines. Hp‐TGM efficiently induced FOXP3 expression (> 60%), in addition to CD25 and CTLA‐4, and caused epigenetic modification of the FOXP3 locus to a greater extent than TGF‐β. Hp‐TGM‐induced Tregs had superior suppressive function compared with TGF‐β‐induced Tregs, and retained their phenotype following exposure to inflammatory cytokines. Furthermore, Hp‐TGM induced a Treg‐like phenotype in in vivo differentiated Th1 and Th17 cells, indicating its potential to re‐program memory cells to enhance immune tolerance. These data indicate Hp‐TGM has potential to be used to generate stable human FOXP3+ Tregs to treat IBD and other inflammatory diseases. [ABSTRACT FROM AUTHOR]

Regulatory T cells (Tregs) have a critical role in maintaining self‐tolerance and immune homeostasis. There is much interest in using Tregs as a cell therapy to re‐establish tolerance in conditions such as inflammatory bowel disease and type 1 diabetes, with many ongoing clinical studies testing the safety and efficacy of this approach. Manufacturing of Tregs for therapy typically involves ex vivo expansion to obtain sufficient cell numbers for infusion and comes with the risk of altering the activity of key biological processes. However, this process also offers an opportunity to tailor Treg function to maximize in vivo activity. In this review, we focus on the roles of antigen‐presenting cells (APCs) in the generation and function of Tregs in humans. In addition to stimulating the development of Tregs, APCs activate Tregs and provide signals that induce specialized functional and homing marker expression. Cross talk between Tregs and APCs is a critical, often under‐appreciated, aspect of Treg biology, with APCs mediating the key properties of infectious tolerance and bystander suppression. Understanding the biology of human Treg‐APC interactions will reveal new ways to optimize Treg‐based therapeutic approaches. [ABSTRACT FROM AUTHOR]

Inflammatory bowel diseases (IBD) are chronic conditions that result from uncontrolled intestinal inflammation. Pathogenic Th17 cells, characterized by production of IL‐17A in the absence of IL‐10, are thought to contribute to this inflammation, but in humans, antibody‐mediated blockade of IL‐17A is an ineffective IBD therapy whereas IL‐23 blockade is effective. Here, we investigated the effects of pharmacological inhibition of RORC2, the Th17 cell lineage‐defining transcription factor, on in vivo‐differentiated human Th17 cells and Th17‐like Tregs (Th17‐Tregs). BMS‐336, a small molecule RORC2 inverse agonist, inhibited expression of RORC2‐regulated genes in peripheral Th17 cells (CD4+CD25–CD127+CXCR3–CCR4+CCR6+) in a dose–dependent manner, with similar inhibitory effects on laminar propria mononuclear cells from IBD and non‐IBD subjects. Exposure of peripheral Th17‐Tregs (CD4+CD25hiCD127loCXCR3–CCR4+CCR6+) to BMS‐336 also inhibited IL‐17A production and prevented inflammatory cytokine‐induced destabilization, as evidenced by preserved FOXP3 expression and epigenetic status of the Treg‐specific demethylation region. In parallel, RORC2 inhibition increased the production of IL‐10 in Th17‐Tregs, resulting in enhanced suppression of inflammatory cytokines from myeloid cells. Thus, via its ability to simultaneously inhibit Th17 cells and enhance the stability and function of Th17‐Tregs, pharmacological inhibition of RORC2 is a promising approach to suppress inflammation and promote immune regulation in IBD. [ABSTRACT FROM AUTHOR]

Summary: Regulatory T (Treg) cell‐specific deletion of a gene of interest is a procedure widely used to study mechanisms controlling Treg development, homeostasis and function. Accordingly, several transgenic mouse lines have been generated that bear the Cre recombinase under control of the Foxp3 promoter either as a random transgene insertion or knocked into the endogenous Foxp3 locus, with the Foxp3YFP‐Cre strain of mice being one of the most widely used. In an attempt to generate Treg cells that lacked expression of the insulin receptor (Insr), we crossed Foxp3YFP‐Cre mice with Insrfl/fl mice. Using a conventional two‐band PCR genotyping method we found that offspring genotypes did not correspond to the expected Mendelian ratios. We therefore developed a quantitative PCR‐based genotyping method to investigate possible ectopic recombination outside the Treg lineage. With this method we found that ~50% of the F1‐generation mice showed evidence of ectopic recombination and that ~10% of the F2‐generation mice had germline Cre recombination activity leading to a high frequency of offspring with global Insr deletion. Use of the quantitative PCR genotyping method enabled accurate selection of mice without ectopic recombination and only the desired Treg cell‐specific Insr deletion. Our data highlight the need to use genotyping methods that allow for assessment of possible ectopic recombination driven by the Foxp3YFP‐Cre allele, particularly when studying genes that are systemically expressed. [ABSTRACT FROM AUTHOR]

Obesity‐associated visceral adipose tissue (AT) inflammation promotes insulin resistance and type 2 diabetes (T2D). In mice, lean visceral AT is populated with anti‐inflammatory cells, notably regulatory T cells (Tregs) expressing the IL‐33 receptor ST2. Conversely, obese AT contains fewer Tregs and more proinflammatory cells. In humans, however, there is limited evidence for a similar pattern of obesity‐associated immunomodulation. We used flow cytometry and mRNA quantification to characterize human omental AT in 29 obese subjects, 18 of whom had T2D. Patients with T2D had increased proportions of inflammatory cells, including M1 macrophages, with positive correlations to body mass index. In contrast, Treg frequencies negatively correlated to body mass index but were comparable between T2D and non‐T2D individuals. Compared to human thymic Tregs, omental AT Tregs expressed similar levels of FOXP3, CD25, IKZF2, and CTLA4, but higher levels of PPARG, CCR4, PRDM1, and CXCL2. ST2, however, was not detectable on omental AT Tregs from lean or obese subjects. This is the first comprehensive investigation into how omental AT immunity changes with obesity and T2D in humans, revealing important similarities and differences to paradigms in mice. These data increase our understanding of how pathways of immune regulation could be targeted to ameliorate AT inflammation in humans. The proportion of regulatory T cells (Tregs) in human omental adipose tissue decreases in obesity. These human omental adipose Tregs exhibit a tissue‐specific phenotype but lack ST2 expression, in contrast to Tregs resident in mouse epididymal adipose tissue. [ABSTRACT FROM AUTHOR]

Obesity and type-2 diabetes (T2D) are associated with metabolic defects and inflammatory processes in fat depots. FoxP3+ regulatory T cells (Tregs) control immune tolerance, and have an important role in controlling tissue-specific inflammation. In this mini-review we will discuss current insights into how cross-talk between T cells and adipose tissue shapes the inflammatory environment in obesity-associated metabolic diseases, focusing on the role of CD4+T cells and Tregs. We will also highlight potential opportunities for how the immunoregulatory properties of Tregs could be harnessed to control inflammation in obesity and T2D and emphasize the critical need for more research on humans to establish mechanisms that are conserved in both mice and humans. [ABSTRACT FROM AUTHOR]

Treg cells control immune responses to self and nonharmful foreign antigens. Emerging data from animal models indicate that Treg cells function in both secondary lymphoid organs and tissues, and that these different microenvironments may contain specialized subsets of Treg cells with distinct mechanisms of action. The design of therapies for the restoration of tissue-localized immune homeostasis is dependent upon understanding how local immune responses are influenced by Treg cells in health versus disease. Here we review the current state of knowledge about human Treg cells in four locations: the skin, lung, intestine, and joint. Despite the distinct biology of these tissues, there are commonalities in the biology of their resident Treg cells, including phenotypic and functional differences from circulating Treg cells, and the presence of cytokine-producing (e.g. IL-17+) FOXP3+ cells. We also highlight the challenges to studying tissue Treg cells in humans, and opportunities to use new technologies for the detailed analysis of Treg cells at the single-cell level. As emerging biological therapies are increasingly targeted toward tissue-specific effects, it is critical to understand their potential impact on local immune regulation. [ABSTRACT FROM AUTHOR]

Intestinal epithelial cells ( IECs) normally promote the development of gut resident tolerogenic dendritic cells ( DCs) and regulatory T cells, but how this process is altered in inflammatory bowel disease is not well characterized. Recently, we published that the cell injury signal ATP modulates IEC chemokine responses to the TLR5 ligand flagellin and exacerbates colitis in the presence of flagellin. We hypothesized that ATP switches these IECs from tolerogenic to proinflammatory, enhancing DC activation and immune responses to commensal antigens. Here, we report that ATP enhanced murine IEC production of KC, IL-6, TGF-β, and thymic stromal lymphopoietin in response to TLR1/2 stimulation by Pam3CSK4 ( PAM). Moreover, supernatants from IECs stimulated with ATP+ PAM enhanced expression of CD80 on bone marrow derived dendritic cells, and increased their production of IL-12, IL-6, IL-23, TGF-β, and aldh1a2, suggesting a Th1/ Th17 polarizing environment. DCs conditioned by stressed IECs stimulated an enhanced recall response to flagellin and supported the expansion of IFN-γ+ and IL-17+ memory T cells. Lastly, colonic administration of nonhydrolysable ATP increased production of IL-6 and Cxcl1 ( KC) by IECs. These findings indicate that ATP influences the response of IECs to TLR ligands and biases the maturation of DCs to become inflammatory. [ABSTRACT FROM AUTHOR]

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]

The suppression of inappropriate immune responses by Treg cells is one of the major ways that the body maintains immune tolerance and homeostasis. Since defects in the suppressive capacity of Treg cells underlie many different immune-mediated diseases, there is great interest in developing ways to track the number and function of Treg cells as biomarkers of tolerance and in devising ways to enhance their function therapeutically. However, the methods of studying human Treg cells are fraught with technical challenges that can often lead to misinterpretation. The most common way to determine the suppressive capacity of human Treg cells is to measure their ability to suppress the proliferation of responding CD4+ T cells. Here, we discuss the technical considerations that must be taken into account when performing suppression of T-cell proliferation assays with human Treg cells. We also consider how T cells may falsely appear suppressive because of dying cells in the system, improper resting of T-cell lines prior to the assay, or insufficient proliferation of the responding T cells. We propose that, in the future, classification of a population of cells as 'regulatory' should rely on more than a simple test for blockade of CD4+ T-cell proliferation. [ABSTRACT FROM AUTHOR]

CD4+CD25+Foxp3+ regulatory T (TREG) cells are critical mediators of peripheral immune tolerance, and abrogation of their function provokes a variety of autoimmune and inflammatory states including inflammatory bowel disease. In this study, we investigate the functional dynamics of TREG-cell responses in a CD4+ T-cell-induced model of intestinal inflammation in αβ T-cell-deficient (TCR-β−/−) hosts to gain insights into the mechanism and cellular targets of suppression in vivo. We show that CD4+ T effector cell transfer into T-cell-deficient mice rapidly induces mucosal inflammation and colitis development, which is associated with prominent Th1 and Th17 responses. Interestingly, we unveil a prominent role for resident γδ T cells in mucosal inflammation as they promote Th1 and particularly Th17 responses in the early phase of inflammation, thus exacerbating colitis development. We further demonstrate that CD4+CD25+Foxp3+ TREG cells readily inhibit these responses and mediate disease protection, which correlates with their accumulation in the draining LN and lamina propria. Moreover, TREG cells can directly suppress γδ T-cell expansion and cytokine production in vitro and in vivo, suggesting a pathogenic role of γδ T cells in intestinal inflammation. Thus, functional alterations in TREG cells provoke dysregulated CD4+ and γδ T-cell responses to commensal antigens in the intestine. [ABSTRACT FROM AUTHOR]

Invariant natural killer T (iNKT) cells are known to constitutively express the high affinity interlukin-2 receptor α chain (CD25) in neonates, but the functional consequence of this phenotype is unknown. Here, we show that high numbers of CD25-expressing iNKT cells are present early in gestation and represent a significant proportion of the developing immune system. Despite their activated phenotype, neonatal iNKT cells express high levels of the Krüppel-like factor-2, a transcription factor associated with quiescent T cells, and require de novo T-cell receptor and CD28 co-stimulation to proliferate. In contrast to bona fide CD4/CD25-expressing regulatory T cells, neonatal iNKT cells do not suppress T-cell responses, indicating that they do not represent an immunosuppressive cell subset. Evidence that neonatal iNKT cells respond to dramatically reduced amounts of CD1d-restricted antigen compared with adult iNKT cells or T cells, and that their proliferation can be induced in the absence of early interleukin-2 suggest that constitutive expression of CD25 ‘primes’ neonatal iNKT cells to respond rapidly to low amounts of antigen. This unique phenotype, which is distinct from adult iNKT cells, as well as other CD25-expressing activated T or regulatory T cells, may be important to ensure stability of a structurally limited peripheral iNKT-cell repertoire early in life. [ABSTRACT FROM AUTHOR]

We have previously shown that human Th17 lymphocytes are characterized by the selective expression of IL-23 receptor (IL-23R), CCR6, CD161, and the transcription factor retinoic acid-related orphan receptor C (RORC), and originate from a CD161CD4 naïve T-cell precursor in response to the combined activity of IL-1β and IL-23. We show here that not only CD4TCRαβ, but also CD8TCRαβ, CD4CD8 TCRαβ, and CD4CD8 TCRγδ circulating lymphocytes that produce IL-17 express the distinctive marker CD161 on their surface. In addition, we demonstrate that CD161 expression identifies CD8 and CD4CD8 umbilical cord blood T cells that already express RORC and IL-23R mRNA and that can be induced to differentiate into IL-17-producing cells in the presence of IL-1β and IL-23. Finally, we provide evidence that umbilical cord blood naïve CD4CD161 T cells, upon lentivirus-mediated transduction with RORC2 can acquire the ability to express IL-23R, IL-1RI, and CD161, as well as to produce IL-17. Taken together, these data allow to conclude that T-cell subsets able to produce IL-17, as well as precursors of IL-17-producing T cells, exhibit surface expression of CD161, and that this feature is at least in part RORC2-dependent. [ABSTRACT FROM AUTHOR]

Two related chronic inflammatory diseases, Crohn’s disease and ulcerative colitis, are together often referred to as inflammatory bowel disease (IBD). Current treatment options are not curative, and patients face lifelong therapy and debilitation. IBD is thought to be the product of a combination of genetic and environmental factors that result in the abnormal regulation of immune responses. Experimental models have demonstrated that normal CD4+ T-regulatory (Treg) cell responses and commensal bacteria are required for the maintenance of gut immune homeostasis. Recent evidence that CD4+ T cells express Toll-like receptors (TLRs) and respond directly to TLR ligands, suggests that signals from commensal bacteria may directly affect T-cell responses in the gut. In this review, we focus on evidence that defects in Treg cells may underlie IBD in humans. In addition, we discuss evidence that direct signaling via TLRs to T cells can affect IBD and that T-cell-dependent responses to bacterial proteins, such as flagellin, are central to the aetiology of this disease. [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]

A major goal in transplantation immunology is to develop strategies that can specifically promote tolerance to foreign cells and tissues without compromising other immune functions. Experimental induction of transplantation tolerance by dendritic cells (DCs) and/or T regulatory (Treg) cells can efficiently prevent graft-versus-host disease and organ graft rejection in animal models, and there is much hope that similar strategies in transplanted patients will provide an alternative to immunosuppression. Photodynamic therapy (PDT) is a therapeutic treatment for graft versus host disease and organ rejection that may operate via induction of tolerance. We investigated whether a new PDT therapy, based on exposure of cells to 4,5-dibromorhodamine methyl ester (TH9402), may operate via induction of tolerogenic DC. We developed an in vitro model to mimic the in vivo effect of re-infusing peripheral blood mononuclear cells (PBMCs) treated with PDT based on TH9402 (TH-PDT). TH-PDT-treated PBMCs were co-cultured with allogeneic immature monocyte-derived DCs. After 24 h, the phenotype and T-cell stimulatory capacity of the DCs was assessed. Following phagocytosis of TH-PDT PBMCs, DCs maintained an immature phenotype, produced significantly increased amounts of interleukin-10, and had a reduced allostimulatory capacity in comparison to mature DCs. In the context of transplantation, these data suggest that repeated exposure of circulating DCs to TH-PDT PBMCs may result in presentation of alloantigens under anti-inflammatory conditions and induction of antigen-specific tolerance. J. Clin. Apheresis, 2008. © 2008 Wiley-Liss, Inc. [ABSTRACT FROM AUTHOR]

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-β(TGF-β), 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. [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]

Discusses the modulation of sphingolipid metabolism to reverse inherited retinal degeneration. Investigation of the role of modulations to the sphingolipid pathway on retinal degeneration; Genes in which mutations causes inherited retinal degenerative disorders; Neurodegenerative disorder in which ceramide accumulation is observed.

Analyses whether Foxp3, a family transcriptional regulator that functions within a specific subpopulation of T cells, can be used as a therapy for autoimmune disease. Features of the condition that results in multiple autoimmune disorders; Basis of the conclusion that Foxp3 is a master-switch in the development of regulatory cells of the immune system.