CD4(+)CD62L(+) central memory T cells can be converted to Foxp3(+) T cells.
ABSTRACT: The peripheral Foxp3(+) Treg pool consists of naturally arising Treg (nTreg) and adaptive Treg cells (iTreg). It is well known that naive CD4(+) T cells can be readily converted to Foxp3(+) iTreg in vitro, and memory CD4(+) T cells are resistant to conversion. In this study, we investigated the induction of Foxp3(+) T cells from various CD4(+) T-cell subsets in human peripheral blood. Though naive CD4(+) T cells were readily converted to Foxp3(+) T cells with TGF-? and IL-2 treatment in vitro, such Foxp3(+) T cells did not express the memory marker CD45RO as do Foxp3(+) T cells induced in the peripheral blood of Hepatitis B Virus (HBV) patients. Interestingly, a subset of human memory CD4(+) T cells, defined as CD62L(+) central memory T cells, could be induced by TGF-? to differentiate into Foxp3(+) T cells. It is well known that Foxp3(+) T cells derived from human CD4(+)CD25(-) T cells in vitro are lack suppressive functions. Our data about the suppressive functions of CD4(+)CD62L(+) central memory T cell-derived Foxp3(+) T cells support this conception, and an epigenetic analysis of these cells showed a similar methylation pattern in the FOXP3 Treg-specific demethylated region as the naive CD4(+) T cell-derived Foxp3(+) T cells. But further research showed that mouse CD4(+) central memory T cells also could be induced to differentiate into Foxp3(+) T cells, such Foxp3(+) T cells could suppress the proliferation of effector T cells. Thus, our study identified CD4(+)CD62L(+) central memory T cells as a novel potential source of iTreg.
Project description:Under physiological conditions, CD4+ regulatory T (Treg) cells expressing the transcription factor Foxp3 are generated in the thymus [thymus-derived Foxp3+ Treg (tTregs) cells] and extrathymically at peripheral sites [peripherally induced Foxp3+ Treg (pTreg) cell], and both developmental subsets play non-redundant roles in maintaining self-tolerance throughout life. In addition, a variety of experimental in vitro and in vivo modalities can extrathymically elicit a Foxp3+ Treg cell phenotype in peripheral CD4+Foxp3- T cells, which has attracted much interest as an approach toward cell-based therapy in clinical settings of undesired immune responses. A particularly notable example is the in vitro induction of Foxp3 expression and Treg cell activity (iTreg cells) in initially naive CD4+Foxp3- T cells through T cell receptor (TCR) and IL-2R ligation, in the presence of exogenous TGF-?. Clinical application of Foxp3+ iTreg cells has been hampered by the fact that TGF-?-driven Foxp3 induction is not sufficient to fully recapitulate the epigenetic and transcriptional signature of in vivo induced Foxp3+ tTreg and pTreg cells, which includes the failure to imprint iTreg cells with stable Foxp3 expression. This hurdle can be potentially overcome by pharmacological interference with DNA methyltransferase activity and CpG methylation [e.g., by the cytosine nucleoside analog 5-aza-2'-deoxycytidine (5-aza-dC)] to stabilize TGF-?-induced Foxp3 expression and to promote a Foxp3+ iTreg cell phenotype even in the absence of added TGF-?. However, the molecular mechanisms of 5-aza-dC-mediated Foxp3+ iTreg cell generation have remained incompletely understood. Here, we show that in the absence of exogenously added TGF-? and IL-2, efficient 5-aza-dC-mediated Foxp3+ iTreg cell generation from TCR-stimulated CD4+Foxp3- T cells is critically dependent on TGF-?R and IL-2R signaling and that this process is driven by TGF-? and IL-2, which could either be FCS derived or produced by T cells on TCR stimulation. Overall, these findings contribute to our understanding of the molecular mechanisms underlying the process of Foxp3 induction and may provide a rational basis for generating phenotypically and functionally stable iTreg cells.
Project description:Regulatory T-cells (Tregs) are vital for maintaining immunological self-tolerance, and the transcription factor FOXP3 is considered critical for their development and function. Peripheral Treg induction may significantly contribute to the total Treg pool in healthy adults, and this pathway may be enhanced in thymic-deficient conditions like multiple sclerosis (MS). Here, we evaluated iTreg formation from memory versus naïve CD4(+)CD25(-) T-cell precursors. We report the novel finding that memory T-cells readily expressed CD25 and FOXP3, and demonstrated significantly greater suppressive function. Additionally, the CD25(-)FOXP3(-) fraction of stimulated memory T-cells also displayed robust suppression not observed in naïve counterparts or ex vivo resting (CD25(-)) T-cells. This regulatory population was present in both healthy subjects and clinically-quiescent MS patients, but was specifically deficient during disease exacerbation. These studies indicate that iTreg development and function are precursor dependent. Furthermore, MS quiescence appears to correlate with restoration of suppressive function in memory-derived CD4(+)CD25(-)FOXP3(-) iTregs.
Project description:Acute graft-versus-host disease (GvHD) is a major cause of mortality in allogeneic bone marrow transplantation (BMT), for which administration of FoxP3(+) regulatory T (Treg) cells has been proposed as a therapy. However, the phenotypic stability of Treg cells is controversial, and STAT3-dependent cytokines can inhibit FoxP3 expression. We assessed whether the elimination of STAT3 in T cells could limit the severity of GvHD. We found STAT3 limited FoxP3(+) Treg cell numbers following allogeneic BMT by two pathways: instability of natural Treg (nTreg) cells and inhibition of induced Treg (iTreg) cell polarization from naive CD4(+) T cells. Deletion of STAT3 within only the nTreg cell population was not sufficient to protect against lethal GvHD. In contrast, transfer of STAT3-deficient naive CD4(+) T cells increased FoxP3(+) Treg cells post-BMT and prevented lethality, suggesting that the consequence of STAT3 signaling may be greater for iTreg rather than nTreg cells during GvHD.
Project description:CD4(+)CD25(+)Foxp3(+) regulatory T cells (Treg) play an important role in the induction and maintenance of immune tolerance. Although adoptive transfer of bulk populations of Treg can prevent or treat T cell-mediated inflammatory diseases and transplant allograft rejection in animal models, optimal Treg immunotherapy in humans would ideally use antigen-specific rather than polyclonal Treg for greater specificity of regulation and avoidance of general suppression. However, no robust approaches have been reported for the generation of human antigen-specific Treg at a practical scale for clinical use. Here, we report a simple and cost-effective novel method to rapidly induce and expand large numbers of functional human alloantigen-specific Treg from antigenically naive precursors in vitro using allogeneic nontransformed B cells as stimulators. By this approach naive CD4(+)CD25(-) T cells could be expanded 8-fold into alloantigen-specific Treg after 3 weeks of culture without any exogenous cytokines. The induced alloantigen-specific Treg were CD45RO(+)CCR7(-) memory cells, and had a CD4(high), CD25(+), Foxp3(+), and CD62L (L-selectin)(+) phenotype. Although these CD4(high)CD25(+)Foxp3(+) alloantigen-specific Treg had no cytotoxic capacity, their suppressive function was cell-cell contact dependent and partially relied on cytotoxic T lymphocyte antigen-4 expression. This approach may accelerate the clinical application of Treg-based immunotherapy in transplantation and autoimmune diseases.
Project description:CD4(+)Foxp3(+) regulatory T cells (Treg) are critical regulators of immune homeostasis and self-tolerance. Whereas thymic-derived or natural Treg stably express Foxp3, adaptive or induced Treg (iTreg) generated from peripheral CD4 T cells are susceptible to inflammation-induced reversion to pathogenic effector T cells. Building upon our previous observations that T cell-expressed receptors for C3a (C3aR) and C5a (C5aR) drive Th1 maturation, we tested the impact of C3aR/C5aR signaling on induction and stability of alloreactive iTreg. We observed that genetic deficiency or pharmacological blockade of C3aR/C5aR signaling augments murine and human iTreg generation, stabilizes Foxp3 expression, resists iTreg conversion to IFN-?/TNF-?-producing efffector T cells, and, as a consequence, limits the clinical expression of graft-versus-host disease. Taken together, the findings highlight the expansive role of complement as a crucial modulator of T cell alloimmunity and demonstrate proof-of-concept that targeting C3a/C3aR and C5a/C5aR interactions could facilitate iTreg-mediated tolerance to alloantigens in humans.
Project description:BACKGROUND: Celiac disease (CD) is an intestinal inflammation driven by gluten-reactive CD4(+) T cells. Due to lack of selective markers it has not been determined whether defects in inducible regulatory T cell (Treg) differentiation are associated with CD. This is of importance as changes in numbers of induced Treg could be indicative of defects in mucosal tolerance development in CD. Recently, we have shown that, after encounter of retinoic acid during differentiation, circulating gut-imprinted T cells express CD62L(neg)CD38(+). Using this new phenotype, we now determined whether alterations occur in the frequency of natural CD62L(+)Foxp3(+) Treg or mucosally-imprinted CD62L(neg)CD38(+)Foxp3(+) Treg in peripheral blood of CD patients. In particular, we compared pediatric CD, aiming to select for disease at onset, with adult CD. METHODS: Cell surface markers, intracellular Foxp3 and Helios were determined by flow cytometry. Foxp3 expression was also detected by immunohistochemistry in duodenal tissue of CD patients. RESULTS: In children, the percentages of peripheral blood CD4(+)Foxp3(+) Treg were comparable between CD patients and healthy age-matched controls. Differentiation between natural and mucosally-imprinted Treg on the basis of CD62L and CD38 did not uncover differences in Foxp3. In adult patients on gluten-free diet and in refractory CD increased percentages of circulating natural CD62L(+)Foxp3(+) Treg, but normal mucosally-imprinted CD62L(neg)CD38(+)Foxp3(+) Treg frequencies were observed. CONCLUSIONS: Our data exclude that significant numeric deficiency of mucosally-imprinted or natural Foxp3(+) Treg explains exuberant effector responses in CD. Changes in natural Foxp3(+) Treg occur in a subset of adult patients on a gluten-free diet and in refractory CD patients.
Project description:Interplay between Foxp3(+) regulatory T cells (Treg) and dendritic cells (DCs) maintains immunologic tolerance, but the effects of each cell on the other are not well understood. We report that polyclonal CD4(+)Foxp3(+) Treg cells induced ex vivo with transforming growth factor beta (TGF?) (iTreg) suppress a lupus-like chronic graft-versus-host disease by preventing the expansion of immunogenic DCs and inducing protective DCs that generate additional recipient CD4(+)Foxp3(+) cells. The protective effects of the transferred iTreg cells required both interleukin (IL)-10 and TGF?, but the tolerogenic effects of the iTreg on DCs, and the immunosuppressive effects of these DCs were exclusively TGF?-dependent. The iTreg were unable to tolerize Tgfbr2-deficient DCs. These results support the essential role of DCs in 'infectious tolerance' and emphasize the central role of TGF? in protective iTreg/DC interactions in vivo.
Project description:CD4+CD25+ regulatory T cells (Treg) are important mediators of immune tolerance. A subset of Treg can be generated in the periphery by TGF-beta dependent conversion of conventional CD4+CD25- T cells into induced Treg (iTreg). In chronic viral infection or malignancy, such induced iTreg, which limit the depletion of aberrant or infected cells, may be of pathogenic relevance. To identify potential targets for therapeutic intervention, we investigated the TGF-beta signaling in Treg. In contrast to conventional CD4+ T cells, Treg exhibited marked activation of the p38 MAP kinase pathway. Inhibition of p38 MAP kinase activity prevented the TGF-beta-dependent conversion of CD4+CD25- T cells into Foxp3+ iTreg in vitro. Of note, the suppressive capacity of nTreg was not affected by inhibiting p38 MAP kinase. Our findings indicate that signaling via p38 MAP kinase seems to be important for the peripheral generation of iTreg; p38 MAP kinase could thus be a therapeutic target to enhance immunity to chronic viral infection or cancer.
Project description:Adoptive transfer of thymus-derived natural regulatory T cells (nTregs) effectively suppresses disease in murine models of autoimmunity and graft-versus-host disease (GVHD). TGFß induces Foxp3 expression and suppressive function in stimulated murine CD4+25- T cells, and these induced Treg (iTregs), like nTreg, suppress auto- and allo-reactivity in vivo. However, while TGFß induces Foxp3 expression in stimulated human T cells, the expanded cells lack suppressor cell function. Here we show that Rapamycin (Rapa) enhances TGFß-dependent Foxp3 expression and induces a potent suppressor function in naive (CD4+ 25-45RA+) T cells. Rapa/TGFß iTregs are anergic, express CD25 at levels higher than expanded nTregs and few cells secrete IL-2, IFN? or IL-17 even after PMA and Ionomycin stimulation in vitro. Unlike other published methods of inducing Treg function, Rapa/TGFß induces suppressive function even in the presence of memory CD4+ T cells. A single apheresis unit of blood yields an average ~240 × 10? (range ~ 70-560 × 10?) iTregs from CD4+25- T cells in ? 2 weeks of culture. Most importantly, Rapa/TGFß iTregs suppress disease in a xenogeneic model of GVHD. This study opens the door for iTreg cellular therapy for human diseases.
Project description:Induced regulatory T (iTreg) and Th17 cells promote mucosal homeostasis. We used a T cell transfer model of colitis to compare the capacity of iTreg and Th17 cells to develop in situ following the transfer of naive CD4(+)CD45RB(hi)T cells intoRag1(-/-)C57BL/6 or BALB/c mice, the prototypical Th1/M1- and Th2/M2-prone strains. We found that the frequency and number of Foxp3(+)iTreg cells and Th17 cells were significantly reduced in C57BL/6 mice compared with the BALB/c strain. C57BL/6 mice with colitis were also resistant to natural Treg cell immunotherapy. Pretreatment of C57BL/6Rag1(-/-)mice with IL-4 plus IL-13, or with M2a but not M1 macrophages, dramatically increased the generation of iTreg and Th17 cells. Importantly, M2a transfers, either as a pretreatment or in mice with established colitis, allowed successful immunotherapy with natural Treg cells. M2a macrophages also reduced the generation of pathogenic iTreg cells that lost Foxp3 expression, suggesting that they stabilize the expression of Foxp3. Thus, polarized M2a macrophages drive a directionally concordant expansion of the iTreg-Th17 cell axis and can be exploited as a therapeutic adjuvant in cell-transfer immunotherapy to re-establish mucosal tolerance.