Generation of highly effective and stable murine alloreactive Treg cells by combined anti‐CD4 mAb,TGF‐β, and RA treatment

The transfer of alloreactive regulatory T (aTreg) cells into transplant recipients represents an attractive treatment option to improve long‐term graft acceptance. We recently described a protocol for the generation of aTreg cells in mice using a nondepleting anti‐CD4 antibody (aCD4). Here, we investigated whether adding TGF‐β and retinoic acid (RA) or rapamycin (Rapa) can further improve aTreg‐cell generation and function. Murine CD4⁺ T cells were cultured with allogeneic B cells in the presence of aCD4 alone, aCD4+TGF‐β+RA or aCD4+Rapa. Addition of TGF‐β+RA or Rapa resulted in an increase of CD25⁺Foxp3⁺‐expressing T cells. Expression of CD40L and production of IFN‐γ and IL‐17 was abolished in aCD4+TGF‐β+RA aTreg cells. Additionally, aCD4+TGF‐β+RA aTreg cells showed the highest level of Helios and Neuropilin‐1 co‐expression. Although CD25⁺Foxp3⁺ cells from all culture conditions displayed complete demethylation of the Treg‐specific demethylated region, aCD4+TGF‐β+RA Treg cells showed the most stable Foxp3 expression upon restimulation. Consequently, aCD4+TGF‐β+RA aTreg cells suppressed effector T‐cell differentiation more effectively in comparison to aTreg cells harvested from all other cultures, and furthermore inhibited acute graft versus host disease and especially skin transplant rejection. Thus, addition of TGF‐β+RA seems to be superior over Rapa in stabilising the phenotype and functional capacity of aTreg cells.     

Exposure to inflammatory cytokines selectively limits GM‐CSF production by induced T regulatory cells

Interest in manipulating the immunosuppressive powers of Foxp3‐expressing T regulatory cells as an immunotherapy has been tempered by their reported ability to produce proinflammatory cytokines when manipulated in vitro, or in vivo. Understanding processes that can limit this potentially deleterious effect of Treg cells in a therapeutic setting is therefore important. Here, we have studied this using induced (i) Treg cells in which de novo Foxp3 expression is driven by TCR‐stimulation in vitro in the presence of TGF‐β. We show that iTreg cells can produce significant amounts of three proinflammatory cytokines (IFN‐γ, GM‐CSF and TNF‐α) upon secondary TCR stimulation. GM‐CSF is a critical T‐cell derived cytokine for the induction of EAE in mice. Despite their apparent capacity to produce GM‐CSF, myelin autoantigen‐responsive iTreg cells were unable to provoke EAE. Instead, they maintained strong suppressive function in vivo, preventing EAE induction by their CD4⁺Foxp3^? counterparts. We identified that although iTreg cells maintained the ability to produce IFN‐γ and TNF‐α in vivo, their ability to produce GM‐CSF was selectively degraded upon antigen stimulation under inflammatory conditions. Furthermore, we show that IL‐6 and IL‐27 individually, or IL‐2 and TGF‐β in combination, can mediate the selective loss of GM‐CSF production by iTreg cells.     

The GARP/Latent TGF‐β1 complex on Treg cells modulates the induction of peripherally derived Treg cells during oral tolerance

Treg cells can secrete latent TGF‐β1 (LTGF‐β1), but can also utilize an alternative pathway for transport and expression of LTGF‐β1 on the cell surface in which LTGF‐β1 is coupled to a distinct LTGF‐β binding protein termed glycoprotein A repetitions predominant (GARP)/LRRC32. The function of the GARP/LTGF‐β1 complex has remained elusive. Here, we examine in vivo the roles of GARP and TGF‐β1 in the induction of oral tolerance. When Foxp3^? OT‐II T cells were transferred to wild‐type recipient mice followed by OVA feeding, the conversion of Foxp3^? to Foxp3⁺ OT‐II cells was dependent on recipient Treg cells. Neutralization of IL‐2 in the recipient mice also abrogated this conversion. The GARP/LTGF‐β1 complex on recipient Treg cells, but not dendritic cell‐derived TGF‐β1, was required for efficient induction of Foxp3⁺ T cells and for the suppression of delayed hypersensitivity. Expression of the integrin αvβ8 by Treg cells (or T cells) in the recipients was dispensable for induction of Foxp3 expression. Transient depletion of the bacterial flora enhanced the development of oral tolerance by expanding Treg cells with enhanced expression of the GARP/LTGF‐β1 complex.     

Induced regulatory T cells are phenotypically unstable and do not protect mice from rapidly progressive glomerulonephritis

Regulatory T (Treg) cells are a suppressive CD4⁺ T‐cell subset. We generated induced Treg (iTreg) cells and explored their therapeutic potential in a murine model of rapidly progressive glomerulonephritis. Polyclonal naive CD4⁺ T cells were cultured in vitro with interleukin‐2 (IL‐2), transforming growth factor‐β1, all‐trans‐retinoic acid and monoclonal antibodies against interferon‐γ and IL‐4, generating Foxp3⁺ iTreg cells. To enhance their suppressive phenotype, iTreg cultures were modified with the addition of a monoclonal antibody against IL‐12p40 or by using RORγt^–/– CD4⁺ T cells. Induced Treg cells were transferred into models of delayed‐type hypersensitivity and experimental glomerulonephritis. The iTreg cells exhibited comparable surface receptor expression and in vitro suppressive ability to natural Treg cells, but did not regulate antigen‐specific delayed‐type hypersensitivity or systemic inflammatory immune responses, losing Foxp3 expression in vivo. In glomerulonephritis, transferred iTreg cells did not prevent renal injury or modulate systemic T helper type 1 immune responses. Induced Treg cells cultured with anti‐IL‐12p40 had an enhanced suppressive phenotype in vitro and regulated dermal delayed‐type hypersensitivity in vivo, but were not protective against renal injury, losing Foxp3 expression, especially in the transferred cells recruited to the kidney. Use of RORγt^–/– CD4⁺ T cells or iTreg cells generated from sensitized CD4⁺ Foxp3^– cells did not regulate renal or systemic inflammatory responses in vivo. In conclusion, iTreg cells suppress T‐cell proliferation in vitro, but do not regulate experimental glomerulonephritis, being unstable in this inflammatory milieu in vivo.     

Loss of regulatory characteristics in CD4+CD25+/hi T cells induced by impaired transforming growth factor beta secretion in pneumoconiosis

Pneumoconiosis is caused by the accumulation of airborne dust in the lung, which stimulates a progressive inflammatory response that ultimately results in lung fibrosis and respiratory failure. It is possible that regulatory cells in the immune system could function to suppress inflammation and possibly slow or reverse disease progression. However, results in this study suggest that in pneumoconiosis patients, the regulatory T cells (Tregs) and B cells are functionally impaired. First, we found that pneumoconiosis patients presented an upregulation of CD4⁺CD25⁺ T cells compared to controls, whereas the CD4⁺CD25⁺ and CD4⁺CD25^hi T cells were enriched with Th1‐ and Th17‐like cells but not Foxp3‐expressing Treg cells and evidenced by significantly higher T‐bet, interferon (IFN)‐γ, and interleukin (IL)‐17 expression but lower Foxp3 and transforming growth factor (TGF)‐β expression. Regarding the CD4⁺CD25^hi T‐cell subset, the frequency of this cell type in pneumoconiosis patients was significantly reduced compared to controls, together with a reduction in Foxp3 and TGF‐β and an enrichment in T‐bet, RORγt, IFN‐γ, and IL‐17. This skewing toward Th1 and Th17 types of inflammation could be driven by monocytes and B cells, since after depleting CD14⁺ monocytes and CD19⁺ B cells, the levels of IFN‐γ and IL‐17 were significantly decreased. Whole peripheral blood mononuclear cells and isolated monocytes and B cells in pneumoconiosis patients also presented reduced capacity of TGF‐β secretion. Furthermore, monocytes and B cells from pneumoconiosis patients presented reduced capacity in inducing Foxp3 upregulation, a function that could be rescued by exogenous TGF‐β. Together, these data indicated a potential pathway for the progression of pneumoconiosis through a loss of Foxp3⁺ Treg cells associated with impaired TGF‐β secretion.     

Activation rather than Foxp3 expression determines that TGF-β-induced regulatory T cells out-compete naïve T cells in dendritic cell clustering

Regulatory T (Treg) cells are critically important for the maintenance of immunological tolerance. Both centrally arising natural nTreg cells and those emerging in the periphery in response to TGF‐β, iTreg cells, play a role in the control of unwanted immune responses. Treg cells adopt multiple mechanisms to inhibit effector T cells, yet it is unclear whether these mechanisms are shared by nTreg cells and iTreg cells alike. Here, we show that iTreg cells, like nTreg cells, are able to out‐compete naïve T cells in clustering around dendritic cells (DCs). However, using both a tamoxifen‐responsive inducible Foxp3 retroviral construct and TGF‐β‐induced iTreg cells from hCD2‐Foxp3 knock in reporter mice, we show that it is prior antigen‐induced activation rather than Foxp3 expression per se that determines the ability of iTreg cells to competitively cluster around DCs. We found no difference in the capacity of iTreg cells to displace naïve T cells around DCs to that of Tr1, Th1, Th2, or Th9 cells. An important difference was, however, that clustering of iTreg cells around DCs, just as for naïve T cells, did not effectively activate DCs.     

Progesterone suppresses the mTOR pathway and promotes generation of induced regulatory T cells with increased stability

While induced FoxP3⁺ T cells (iTreg cells) are promising cellular therapeutics to treat inflammatory diseases, a limitation in utilizing iTreg cells prepared in vitro is their low stability in inflammatory conditions. Progesterone (P4) is an immune regulatory nuclear hormone with a potent Treg induction activity. We reasoned that this function of progesterone would be utilized to generate iTreg cells with highly suppressive activity and improved stability in vivo. Here we generated iTreg cells with progesterone in vitro and found that progesterone generates iTreg cells that are highly stable in inflammatory conditions. Moreover, P4‐induced iTreg cells highly express latency‐associated peptide TGF‐β1 and are efficient in regulating inflammation in multiple tissues, whereas control iTreg cells induced with TGF‐β1 alone are less stable and ineffective in suppressing inflammation. The function of progesterone in inducing iTreg cells with improved regulatory activity is associated with the function of P4 in suppressing the mTOR pathway. Moreover, the function of progesterone in inducing FoxP3⁺ T cells is decreased but not completely abolished on nuclear progesterone receptor‐deficient T cells, suggesting that both nuclear and nonnuclear progesterone receptors are involved in mediating the function. We conclude that P4 can be utilized to generate iTreg cells with a high therapeutic potential in treatment of tissue inflammation.     

Exosomes with membrane‐associated TGF‐β1 from gene‐modified dendritic cells inhibit murine EAE independently of MHC restriction

We have previously demonstrated that exosomes from dendritic cells (DCs) secreting TGF‐β1 (sTGF‐β1‐EXOs) delay the development of murine inflammatory bowel disease (IBD). In this study, we isolated exosomes from DCs expressing membrane‐associated TGF‐β1 (mTGF‐β1‐EXOs) and found mTGF‐β1‐EXOs had more potent immunosuppressive activity than sTGF‐β1‐EXOs in vitro. Treatment of mice with mTGF‐β1‐EXOs inhibited the development and progression of myelin oligodendrocyte glycoprotein (MOG) peptide‐induced EAE even after disease onset. Treatment of mice with mTGF‐β1‐EXOs also impaired Ag‐specific Th1 and IL‐17 responses, but promoted IL‐10 responses ex vivo. Treatment with mTGF‐β1‐EXOs decreased the frequency of Th17 cells in EAE mice, which might be associated with the down‐regulation of the p38, ERK, Stat3, and NF‐κB activation and IL‐6 expression in DCs. Treatment with mTGF‐β1‐EXOs maintained the regulatory capacity of Treg cells, and adoptive transfer of CD4⁺Foxp3⁺ Treg cells from mTGF‐β1‐EXO‐treated EAE mice dramatically prevented the development of EAE in the recipients. Moreover, treatment with mTGF‐β1‐EXOs from C57BL/6 mice effectively prevented and inhibited proteolipid protein (PLP) peptide‐induced EAE in BALB/c mice. These results indicate that mTGF‐β1‐EXOs possess powerful immunosuppressive ability and can effectively inhibit the development and progression of EAE in different strains of mice.     

Allium sativum‐derived allitridin inhibits treg amplification in cytomegalovirus infection

This study investigated the effects of allitridin compound on murine cytomegalovirus (MCMV)‐induced regulatory T cell (Treg; CD4⁺CD25⁺Foxp3⁺) amplification in vivo and in vitro. One hundred twenty MCMV‐infected mice were allocated at random into two groups for treatment with allitridin or placebo. Another 120 mock‐infected mice were randomly allocated as controls for the allitridin treatment and placebo treatment groups. The mice were euthanized at various time points after infection (out to 120 days) to evaluate the effects of treatment on Treg presence and function, as well as MCMV infective load. Co‐culture with mouse embryo fibroblasts (MEF) and MCMV was performed to evaluate allitridin‐mediated Treg and anti‐CMV effects. The maximum tolerance concentration (MTC) of allitridin was used to treat cells for 3 days. Changes in Foxp3 mRNA and protein levels, percentages of T cell subsets, and Treg‐related cytokines (IL‐10 and TGF‐β) were measured. Allitridin treatment did not influence Foxp3 expression and Treg proportion in uninfected mice, but did down‐regulate each in infected mice during the chronic infection period. Additionally, allitridin treatment reduced the MCMV load in salivary glands. MTC allitridin treatment of co‐cultures partially blocked MCMV induction of Foxp3 mRNA and protein expression. In vitro treatment with allitridin also increased significantly the percentages of Tc1, Tc2, and Th1, reduced the secreted levels of IL‐10 and TGF‐β1, and significantly suppressed viral loads. In conclusion, allitridin can promote MCMV‐induced Treg expansion and Treg‐mediated anti‐MCMV immunosuppression. Therefore, allitridin may be useful as a therapeutic agent to enhance the specific cellular immune responses against CMV. J. Med. Virol. 85:493–500, 2013. © 2013 Wiley Periodicals, Inc.     

HCV‐infected hepatocytes drive CD4+CD25+Foxp3+ regulatory T‐cell development through the Tim‐3/Gal‐9 pathway

HCV is remarkable at disrupting human immunity to establish chronic infection. The accumulation of Treg cells at the site of infection and upregulation of inhibitory signaling pathways (such as T‐cell Ig and mucin domain protein‐3 (Tim‐3) and galectin‐9 (Gal‐9)) play pivotal roles in suppressing antiviral effector T (Teff) cells that are essential for viral clearance. While Tim‐3/Gal‐9 interactions have been shown to negatively regulate Teff cells, their role in regulating Treg cells is poorly understood. To explore how Tim‐3/Gal‐9 interactions regulate HCV‐mediated Treg‐cell development, here we provide pilot data showing that HCV‐infected human hepatocytes express higher levels of Gal‐9 and TGF‐β, and upregulate Tim‐3 expression and regulatory cytokines TGF‐β/IL‐10 in co‐cultured human CD4⁺ T cells, driving conventional CD4⁺ T cells into CD25⁺Foxp3⁺ Treg cells. Additionally, recombinant Gal‐9 protein can transform TCR‐activated CD4⁺ T cells into Foxp3⁺ Treg cells in a dose‐dependent manner. Importantly, blocking Tim‐3/Gal‐9 ligations abrogates HCV‐mediated Treg‐cell induction by HCV‐infected hepatocytes, suggesting that Tim‐3/Gal‐9 interactions may regulate human Foxp3⁺ Treg‐cell development and function during HCV infection.     

Induction and mechanism of action of transforming growth factor-β-secreting Th3 regulatory cells

Summary: Th3 CD4⁺ regulatory cells were identified during the course of investigating mechanisms associated with oral tolerance. Different mechanisms of tolerance are induced following oral antigen administration, including active suppression, clonal anergy and deletion. Low doses favor active suppression whereas high doses favor anergy/deletion. Th3 regulatory cells form a unique T‐cell subset which primarily secretes transforming growth factor (TGF)‐β, provides help for IgA and has suppressive properties for both Th1 and Th2 cells. Th3 type cells are distinct from the Th2 cells, as CD4⁺ TGF‐β‐secreting cells with suppressive properties have been generated from interleukin (IL)‐4‐deficient animals. In vitro differentiation of Th3 cells from Th precursors from T‐cell antigen receptor (TCR) transgenic mice is enhanced by culture with TGF‐β, IL‐4, IL‐10, and anti‐IL‐12. Th3 CD4⁺ myelin basic protein regulatory clones are structurally identical to Th1 encephalitogenic clones in TCR usage, MHC restriction and epitope recognition, but produce TGF‐β with various amounts of IL‐4 and IL‐10. Because Th3 regulatory cells are triggered in an antigen‐specific fashion but suppress in an antigen‐non‐specific fashion, they mediate “bystander suppression” when they encounter the fed autoantigen at the target organ. In vivo induction of Th3 cells and low dose oral tolerance is enhanced by oral administration of IL‐4. Anti‐CD86 but not anti‐CD80 blocks the induction of Th3 cells associated with low dose oral tolerance. Th3 regulatory cells have been described in other systems (e.g. recovery from experimental allergic encephalomyelitis) but may be preferentially generated following oral antigen administration due to the gut immunologic milieu that is rich in TGF‐β and has a unique class of dendritic cells. CD4⁺CD25⁺ regulatory T‐cell function also appears related to TGF‐β.     

DC expressing transgene Foxp3 are regulatory APC

Tolerogenic DC and suppressive Foxp3⁺ Treg play important roles in preventing autoimmunity and allograft rejection. We report that (adenovirus mediated) ectopic expression of Foxp3 in human DC (i.e. DC.Foxp3) yields an APC that severely limits T‐cell proliferation and type‐1 immune responses from the naïve, but not memory, pool of responder T cells in vitro. In marked contrast, the frequencies of type‐2 and Treg responses were dramatically increased after stimulation of naïve T cells with DC.Foxp3 versus control DC. DC.Foxp3‐induced CD4⁺CD25⁺ Treg cells potently suppressed the proliferation of, and IFN‐γ production from, CD4⁺ and CD8⁺ responder T cells. Notably, the immunosuppressive biology of DC.Foxp3 was effectively normalized by addition of 1‐methyl‐tryptophan or neutralizing anti‐TGF‐β1 Ab during the period of T‐cell priming. These data suggest the potential utility of regulatory DC.Foxp3 and/or DC.Foxp3‐induced CD4⁺CD25⁺ Treg as translational agents for the amelioration or prevention of pathology in the setting of allograft transplantation and/or autoimmunity.     

The Ex Vivo Induction of Human CD103+ CD25hi Foxp3+ CD4+ and CD8+ Tregs is IL‐2 and TGF‐β1 Dependent

The expression of the integrin αE (CD103), may enhance the retention of regulatory T cells to peripheral inflammatory sites and possibly contribute to their suppressive potential. The aim of this study was to define the regulatory role of IL‐2 and TGF‐β1 on the CD103 expression and the optimal in vitro conditions for the induction/expansion of human CD4⁺ and CD8⁺ Tregs. Cord blood mononuclear cells (CBMC) were stimulated under various culture conditions, including anti‐CD3, anti‐CD28, IL‐2 and TGF‐β1. TGF‐β1 and IL‐2 were both required for optimal expression of CD103. In addition, TGF‐β1 and IL‐2 synergistically induced CD103 expression on CD8⁺ T cells, whereas, only additive induced expression was noted on CD4⁺ T cells. Surprisingly, CD103 expression was not dependent upon CD28 costimulation. IL‐2 also played a central role in CD103 expression by CD25^hi Foxp3+ Tregs. IL‐2, TGF‐β1 and anti‐CD3 defined the optimal stimulatory conditions favouring the induction/expansion of both CD4⁺ and CD8⁺ human Tregs from naive CBMC. Thus, this study provides new insights into the regulatory role of IL‐2 upon CD103 expression by human cord blood CD4⁺ and CD8⁺ T cells. Furthermore, it identifies the in vitro culture conditions driving the differentiation of the novel phenotype CD4⁺ and CD8⁺ CD103⁺ CD25^hi Foxp3+ Tregs from human CBMC.     

Natural Treg cells spontaneously differentiate into pathogenic helper cells in lymphopenic conditions

Induction of Forkhead‐box p3 (Foxp3) expression in developing T cells upon peptide‐MHC encountering has been proposed to define a lineage of committed Treg cells. However, sustained expression of Foxp3 is required for Treg function and what maintains Foxp3 expression in peripheral Treg remains obscure. To address this issue, we monitored natural Treg phenotype and function upon adoptive transfer into lymphocyte‐deficient mice. We first show that about 50% of Foxp3‐GFP⁺ Treg isolated from Foxp3^gfp KI animals loose Foxp3 expression in severe lymphopenic conditions. We next evidence that the cytokine IL‐2, either produced by co‐transferred conventional T cells or administrated i.v. prevents Foxp3 downregulation. Moreover, we document that Treg that lost Foxp3 expression upon adoptive transfer produce IL‐2 are not suppressive and promote tissue infiltration and damage upon secondary transfer into alymphoid mice. Our findings that Treg convert into pathogenic Th cells in absence of IL‐2 provide new clues to the success of Treg‐based immune therapies.     

Schistosoma mansoni egg antigens induce Treg that participate in diabetes prevention in NOD mice

Schistosoma mansoni soluble egg antigens (SEA) profoundly regulate the infected host's immune system. We previously showed that SEA prevents type 1 diabetes in NOD mice and that splenocytes from SEA‐treated mice have reduced ability to transfer diabetes to NOD.scid recipients. To further characterize the mechanism of diabetes prevention we examined the cell types involved and showed that CD25⁺ T‐cell depletion of splenocytes from SEA‐treated donors restored their ability to transfer diabetes. Furthermore, SEA treatment increased the number and proportional representation of Foxp3⁺ T cells in the pancreas of NOD mice. We have used in vitro systems to analyze the effect of SEA on the development of NOD Foxp3⁺ T cells. We find that SEA can induce Foxp3 expression in naïve T cells in a TGF‐β‐dependent manner. Foxp3 induction requires the presence of DC, which we also show are modified by SEA to upregulate C‐type lectins, IL‐10 and IL‐2. Our studies show that SEA can have a direct effect on CD4⁺ T cells increasing expression of TGF‐β, integrin β8 and galectins. These effects of SEA on DC and T cells may act in synergy to induce Foxp3⁺ Treg in the NOD mouse.     

c‐Rel is crucial for the induction of Foxp3+ regulatory CD4+ T cells but not TH17 cells

The NF‐κB/Rel family member c‐Rel was described to be required for the development of T_H1 responses. However, the role of c‐Rel in the differentiation of T_H17 and regulatory CD4⁺Foxp3⁺ T cells (Treg) remains obscure. Here, we show that in the absence of c‐Rel, in vitro differentiation of pro‐inflammatory T_H17 cells is normal. In contrast, generation of inducible Treg (iTreg) within c‐Rel‐deficient CD4⁺ T cells was severely hampered and correlated to reduced numbers of Foxp3⁺ T cells in vivo. Mechanistically, in vitro conversion of naive CD4⁺ T cells into iTreg was crucially dependent on c‐Rel‐mediated synthesis of endogenous IL‐2. The addition of exogenous IL‐2 was sufficient to rescue the development of c‐Rel‐deficient iTreg. Thus, c‐Rel is essential for the development of Foxp3⁺ Treg but not for T_H17 cells via regulating the production of IL‐2.     

Hypoxic culture conditions enhance the generation of regulatory T cells

The generation of large amounts of induced CD4⁺ CD25⁺ Foxp3⁺ regulatory T (iTreg) cells is of great interest for several immunotherapy applications, therefore a better understanding of signals controlling iTreg cell differentiation and expansion is required. There is evidence that oxidative metabolism may regulate several key signalling pathways in T cells. This prompted us to investigate the effects of oxygenation on iTreg cell generation by comparing the effects of atmospheric (21%) or of low (5%) O₂ concentrations on the phenotype of bead‐stimulated murine splenic CD4⁺ T cells from Foxp3‐KI‐GFP T‐cell receptor transgenic mice. The production of intracellular reactive oxygen species was shown to play a major role in the generation of iTreg cells, a process characterized by increased levels of Sirt1, PTEN and Glut1 on the committed cells, independently of the level of oxygenation. The suppressive function of iTreg cells generated either in atmospheric or low oxygen levels was equivalent. However, greater yields of iTreg cells were obtained under low oxygenation, resulting from a higher proliferative rate of the committed Treg cells and higher levels of Foxp3, suggesting a better stability of the differentiation process. Higher expression of Glut1 detected on iTreg cells generated under hypoxic culture conditions provides a likely explanation for the enhanced proliferation of these cells as compared to those cultured under ambient oxygen. Such results have important implications for understanding Treg cell homeostasis and developing in vitro protocols for the generation of Treg cells from naive T lymphocytes.     

Glucocorticoid hormone differentially modulates the in vitro expansion and cytokine profile of thymic and splenic Treg cells

Objective

Functional disturbances in regulatory T cells (Treg) have been described in autoimmune diseases, and their potential therapeutic use is intensively studied. Our goal was to investigate the influence of glucocorticoid hormone on the in vitro differentiation of Treg cells from thymic and splenic CD4⁺ T cells under different conditions to establish methods for generating stable and functionally suppressive iTregs for future use in adoptive transfer experiments.

Curcumin induces the tolerogenic dendritic cell that promotes differentiation of intestine‐protective regulatory T cells

The gut is home to a large number of Treg, with both CD4⁺ CD25⁺ Treg and bacterial antigen‐specific Tr1 cells present in normal mouse intestinal lamina propria. It has been shown recently that intestinal mucosal DC are able to induce Foxp3⁺ Treg through production of TGF‐β plus retinoic acid (RA). However, the factors instructing DC toward this mucosal phenotype are currently unknown. Curcumin has been shown to possess a number of biologic activities including the inhibition of NF‐κB signaling. We asked whether curcumin could modulate DC to be tolerogenic whose function could mimic mucosal DC. We report here that curcumin modulated BM‐derived DC to express ALDH1a and IL‐10. These curcumin‐treated DC induced differentiation of naïve CD4⁺ T cells into Treg resembling Treg in the intestine, including both CD4⁺CD25⁺ Foxp3⁺ Treg and IL‐10‐producing Tr1 cells. Such Treg induction required IL‐10, TGF‐β and retinoic acid produced by curcumin‐modulated DC. Cell contact as well as IL‐10 and TGF‐β production were involved in the function of such induced Treg. More importantly, these Treg inhibited antigen‐specific T‐cell activation in vitro and inhibited colitis due to antigen‐specific pathogenic T cells in vivo.