Generation Of Tregs Research Articles

Endometrial mesenchymal stem/stromal cells: The Enigma to code messages for generation of functionally active regulatory T cells

BackgroundRegulatory T cells (Tregs) play an important role in fine-tuning of immune responses and are pivotal for a successful pregnancy. Recently, the importance of mesenchymal stem cells in regulation of immune responses in general and Tregs in particular has been highlighted. Here, we hypothesized that menstrual stromal/stem cells (MenSCs) contribute to uterine immune system regulation through induction of functionally active Tregs.MethodsMenSCs were collected from 18 apparently healthy women and characterized. Bone marrow mesenchymal stem cells (BMSCs) served as a control. The effect of MenSCs on proliferation of anti-CD3/CD28-stimulated T CD4 + cells and generation of Tregs with or without pre-treatment with mitomycin C, IFN-γ and IL-1β was evaluated by flow cytometry. The potential role of IDO, PGE2, IL-6, IL-10, and TGF-β on proliferation of T CD4 + cells and generation of Tregs was assessed using blocking antibodies or agents. IDO activity was evaluated in MenSCs and BMSCs culture supernatants by a colorimetric assay. IL-10 and IFN-γ production in MenSCs-primed T CD4 + was measured using intracellular staining. To investigate the functional properties of Tregs induced by MenSCs, Treg cells were isolated and their functional property to inhibit proliferation of anti-CD3/CD28-stimulated PBMCs was assessed by flow cytometry.ResultsAccording to the results, proliferation of T CD4 + lymphocytes was enhanced in the presence of MenSCs, while pre-treatment of MenSCs with pro-inflammatory cytokines reversed this effect. PGE2 and IDO were the major players in MenSCs-induced T cell proliferation. Non-treated MenSCs decreased the frequency of Tregs, whereas after pre-treatment with IFN-γ and IL-1β, they induced functional Tregs with ability to inhibit the proliferation of anti-CD3/CD28-stimulated PBMCs. This effect was mediated through IL-6, IL-10, TGF-β and IDO. IFN-γ/IL-1β-treated MenSCs induced IL-10 and IFN-γ production in CD4 + T cells.ConclusionCollectively, these findings indicate that immunomodulatory impact of menstrual blood stem cells (MenSCs) on generation of Tregs and inhibition of T cells proliferation is largely dependent on pre-treatment with IFN-γ and IL-1β. This is the first report on immunomodulatory impact of MenSCs on Tregs and highlights the pivotal role of endometrial stem cells in regulation of local endometrial immune responses.

The Immunomodulation Potential of Exosomes in Tumor Microenvironment.

Exosomes are lipid bilayer particles that originated from almost all types of cells and play an important role in intercellular communication. Tumor-derived exosomes contain large amounts of noncoding RNA, DNA, and proteins, which can be transferred into recipient cells as functional components in exosomes. These exosomal functional constituents depend on the originating cells, and it has been proved that types and numbers of exosomal components differ in cancer patients and healthy individuals. This review summarizes the role of tumor-derived exosomes in immunomodulation and discusses the application of exosomes in immunotherapy in cancers. Overall, exosomes isolated from cancer cells are turned out to promote immune evasion and interfere with immune responses in tumors through inducing apoptosis of CD8+ T cells, facilitating generation of Tregs, suppressing natural killer (NK) cell cytotoxicity, inhibiting maturation and differentiation of monocyte, and enhancing suppressive function of myeloid-derived suppressor cells (MDSCs). Mechanistically, exosomal functional components play a significant role in the immunomodulation in cancers. Moreover, based on the existing studies, exosomes could potentially serve as therapeutic delivery vehicles, noninvasive biomarkers, and immunotherapeutic vaccines for various types of cancers.

Sex-specific remodeling of T-cell compartment with aging: Implications for rat susceptibility to central nervous system autoimmune diseases

The incidence of multiple sclerosis (MS) and susceptibility of animals to experimental autoimmune encephalomyelitis (EAE), the most commonly used experimental model of MS, decrease with aging. Generally, autoimmune diseases develop as the ultimate outcome of an imbalance between damaging immune responses against self and regulatory immune responses (keeping the former under control). Thus, in this review the age-related changes possibly underlying this balance were discussed. Specifically, considering the central role of T cells in MS/EAE, the impact of aging on overall functional capacity (reflecting both overall count and individual functional cell properties) of self-reactive conventional T cells (Tcons) and FoxP3+ regulatory T cells (Tregs), as the most potent immunoregulatory/suppressive cells, was analyzed, as well. The analysis encompasses three distinct compartments: thymus (the primary lymphoid organ responsible for the elimination of self-reactive T cells – negative selection and the generation of Tregs, compensating for imperfections of the negative selection), peripheral blood/lymphoid tissues (“afferent” compartment), and brain/spinal cord tissues (“target” compartment). Given that the incidence of MS and susceptibility of animals to EAE are greater in women/females than in age-matched men/males, sex as independent variable was also considered. In conclusion, with aging, sex-specific alterations in the balance of self-reactive Tcons/Tregs are likely to occur not only in the thymus/”afferent” compartment, but also in the “target” compartment, reflecting multifaceted changes in both T-cell types. Their in depth understanding is important not only for envisaging effects of aging, but also for designing interventions to slow-down aging without any adverse effect on incidence of autoimmune diseases.

Intranodal Sirolimus Induces Regulatory T Cells in Human Hepatic Lymph Nodes via Interleukin 10 Signaling.

Intranodal Sirolimus Induces Regulatory T Cells in Human Hepatic Lymph Nodes via Interleukin 10 Signaling.

Peritoneal Fluid from Patients with Ovarian Endometriosis Displays Immunosuppressive Potential and Stimulates Th2 Response.

Endometriosis is a common gynaecological disorder characterized by the ectopic growth of endometrial tissue outside the uterine cavity. It is associated with chronic pelvic inflammation and autoimmune reactivity manifesting by autoantibody production and abrogated cellular immune responses. Endometriotic peritoneal fluid contains various infiltrating leucocyte populations and a bulk of proinflammatory and immunoregulatory cytokines. However, the nature and significance of the peritoneal milieu in women with endometriosis still remains obscure. Therefore, the aim of the present study was to investigate the immunoregulatory activity of the peritoneal fluid (PF) from women with endometriosis. The peritoneal fluid samples were collected during laparoscopic surgery from 30 women with and without endometriosis. Immunoregulatory cytokines (IL-2, IL-4, IL-6, IL-10, IL-17A, IFN-γ and TNF) and chemokines (CCL2, CCL5, CXCL8 and CXCL9) were evaluated in PF and culture supernatants generated by unstimulated and CD3/CD28/IL-2-stimulated CD4+ T cells cultured in the presence of PF. The effect of PF on the generation of Treg and Th17 cells in CD4+ T cell cultures, as well as the natural cytotoxic activity of peripheral blood mononuclear cells, was also investigated. Concentrations of IL-6, IL-10, CCL2, CXCL8 and CXCL9 were significantly upregulated in the PF from women with endometriosis when compared to control women, whereas concentrations of other cytokines and chemokines were unaffected. The culturing of unstimulated and CD3/CD28/IL-2-stimulated CD4+ T cells in the presence of endometriotic PF resulted in the downregulation of their IL-2, IFN-γ, IL-17A and TNF production as compared to culture medium alone. On the other side, endometriotic PF significantly stimulated the production of IL-4 and IL-10. Endometriotic PF also stimulated the release of CCL2 and CXCL8, whereas the production of CCL5 and CXCL9 was downregulated. Endometriotic PF stimulated the generation of Treg cells and had an inhibitory effect on the generation of Th17 cells in cultures of CD4+ T cells. It also inhibited the NK cell cytotoxic activity of the peripheral blood lymphocytes. These results strongly imply that the PF from patients with endometriosis has immunoregulatory/immunosuppressive activity and shifts the Th1/Th2 cytokine balance toward the Th2 response, which may account for deviation of local and systemic immune responses. However, a similar trend, albeit not a statistically significant one, was also observed in case of PF from women without endometriosis, thus suggesting that peritoneal milieu may in general display some immunoregulatory/immunosuppressive properties. It should be stressed, however, that our present observations were made on a relatively small number of PF samples and further studies are needed to reveal possible mechanism(s) responsible for this phenomenon.

Aucuboside Inhibits the Generation of Th17 Cells in Mice Colitis.

Aucuboside is an iridoid glycoside extracted from traditional Chinese medicine such as Rehmannia glutinosa, possessing a wide range of biological activities, including antioxidant, anti-aging, anti-inflammatory, and anti-fibrotic effects. The effects of aucuboside on inflammatory bowel disease (IBD) have not been studied. Therefore, the effects of aucuboside on the generation of Foxp3+ regulatory T (Treg) cells and IL-17–producing T helper (Th17) cells in colitis were studied. A mouse colitis model was established by intracolonic administration of 2,4,6-trinitrobenzene sulfonic acid (TNBS) to mimic human IBD. The generation of Treg and Th17 cells was evaluated by flow cytometry. Aucuboside significantly alleviated colitis symptoms, including weight loss, high disease activity index, and inflammatory responses. The generation of Th17 cells in colitis was significantly inhibited by aucuboside and accompanied by the suppression of IL-17 expression. In Raw264.7 cells, the LPS-induced increase in IL-17 expression was also suppressed by aucuboside, which was significantly blocked by the RORγt inhibitor sr2211. In addition, the decrease in the proportion of Treg cells was also partially reversed by aucuboside, which may reflect the aucuboside-induced inhibition of Th17 cells. This previously unrecognized immunoregulatory function of aucuboside may have clinical applications in IBD.

Abstract 1267: Combination therapy of JNJ-67856633, a novel, first-in-class MALT1 protease inhibitor, and JNJ-64264681, a novel BTK inhibitor, for the treatment of B-cell lymphomas

Abstract Background: Constitutive activation of the classical nuclear factor kappa-light-chain-enhancer of activated B-cells (NF-κB) pathway is a clear driver of B-cell non-Hodgkin lymphomas (NHL). Bruton's Tyrosine Kinase (BTK) and Mucosa-associated lymphoid tissue lymphoma translocation protein 1 (MALT1), which lies downstream of BTK, are key mediators of the classical NF-κB signaling pathway activated by BCR and TCR receptors. JNJ-67856633 is a first-in-class MALT1 protease inhibitor. JNJ-64264681 is a BTK inhibitor with improved selectivity against BTK. Blocking the BCR pathway at multiple points using these two orally bioavailable compounds could enhance clinical activity in B-cell lymphoma patients. Methods: JNJ-67856633 and JNJ-64264681 are currently being evaluated in phase 1 clinical trials designed to establish safety, PK, PD and the Recommended Phase 2 Dose (RP2D) of each agent. Results: JNJ-67856633 is a potent, selective, orally bioavailable, allosteric inhibitor of MALT1 protease activity. The compound inhibits proliferation of activated B-cell diffuse large B-cell lymphoma (ABC-DLBCL) cell lines bearing CD79b or CARD11 mutations as well as models mimicking resistance to covalent BTK inhibitors. JNJ-67856633 exhibits potent tumor growth inhibition in two human DLBCL xenograft models, OCI-Ly3 and OCI-Ly10, and mutation selected patient derived DLBCL xenografts. Furthermore, treatment with JNJ-67856633 leads to dose dependent inhibition of the generation of Tregs (CD4+CD25+FoxP3+) following CD3/28 stimulation in vitro, suggesting a potential immune modulatory role of MALT1 inhibition. JNJ-64264681 is an orally active small molecule that is a potent, selective, and irreversible covalent BTK inhibitor. JNJ-64264681 inhibits the growth of CD79b-mutant DLBCL cell lines in vitro and potently inhibits tumor growth in xenograft- or patient-derived DLBCL models in vivo. Treatment with JNJ-64264681 and JNJ-67856633 administered together demonstrated statistically significant tumor growth inhibition compared with vehicle control in two CD79b mutant mouse lymphoma models, one based on a DLBCL cell line (OCI-Ly10) and one based on a patient-derived DLBCL model (LY2298). In both models, the combination showed increased growth inhibition compared with single agents and tumor regression in the combination arm. Synergistic anti-proliferative activity was observed in three DLBCL cell lines carrying CD79b mutations and one MCL cell line. Conclusions: Taken together, the in vitro and in vivo data for JNJ-67856633 and JNJ-64264681 suggest that combination therapy can increase the anti-tumor effect of the monotherapies and provide a more sustained response, offering strong support for clinical investigation of the combination of these two novel agents. A phase 1b combination study is scheduled to initiate. Citation Format: Ulrike Philippar, Lorena Fontan, Ivo Cornelissen, Haopeng Rui, Sriram Balasubramanian, Marcello Gaudiano, Mariette Bekkers, Luc Van Nuffel, Tianbao Lu, Tianbao Lu, John Wiener, Mark Tichenor, Tony Greway, Kathryn Packman, Bie Verbist, Yusri Elsayed, Ricardo Attar, Jacqueline Bussolari, John Gerecitano. Combination therapy of JNJ-67856633, a novel, first-in-class MALT1 protease inhibitor, and JNJ-64264681, a novel BTK inhibitor, for the treatment of B-cell lymphomas [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1267.

Complement Promotes Gvhd through Suppressing Autophagy in Recipient Dendritic Cells after Allogeneic Hematopoietic Cell Transplantation in Mice

Graft-versus-host disease (GVHD) limits the success of allogeneic hematopoietic stem cell transplantation (allo-HCT). Traditional therapies have targeted T cells, yet immunostimulatory dendritic cells (DCs) are critical in the pathogenesis of GVHD. Autophagy is a self-degradative process for cytosolic components and is required for maintaining homeostasis after allo-HCT. Complement receptors C3aR/C5aR can regulate immune responses by translating information gathered by complement fluid phase sensors into cellular responses. C3aR/C5aR have been reported to activate the autophagy inhibitor mTOR in cells. While depletion of autophagy in recipient DCs aggravates GVHD severity, and enhancing autophagy represents as a promising approach for treating immunological diseases, it is not known how escalation of autophagy regulates DC-functionality in GVHD pathogenesis. In the current study, we found that deficiency of C3aR/C5aR signaling significantly upregulated mTOR-independent autophagy in DCs (Figure 1B), which is associated with increased apoptosis, and reduced activation and antigen presenting capacity of C3aR/C5aR-/-DCs (Figure 1, A-C).To evaluate the role of C3aR/C5aR in modulating DC function in GVHD pathogenesis, we compared the severity of GVHD in WT versus C3aR/C5aR-/- recipients using murine models of allo-HCT. C3aR/C5aR-/- recipients developed less severe GVHD than their WT counterparts, reflected by a significantly higher rate of survival and lower clinical scores (Figure 1D). Donor T-cell survival and Th1-differentiation were significantly decreased, whereas Treg generation was increased in C3aR/C5aR-/- recipients. Glycolytic activity of donor T cells was significantly abrogated in the absence of recipient C3aR/C5ar (Figure 1E). Donor T-cells expressed lower levels of chemokine receptors, CXCR3 and CCR6, which were likely contributed to the decreased migration of the effector T cells into GVHD target organs of C3aR/C5aR-/- recipients. Using chimeric recipients in which either the hematopoietic or non-hematopoietic compartment is deficient for C3aR/C5aR, we found that C3aR/C5aR in the recipient hematopoietic cells was primarily responsible for donor T-cell response and pathogenicity in GVHD. Transfusion of C3aR/C5aR-/- DCs along with allo-HCT mitigated GVHD severity, indicating that C3aR/5aR signaling in DCs plays a predominant role in the pathogenesis of GVHD. Elevated autophagy was required for the suppressive effect of C3aR/C5aR-/- DCs on GVHD as autophagy inhibitor chloroquine (CQ) reverted the GVHD-suppressive effect of C3aR/C5aR-/-DCs (Figure 1F). For translational purpose, we evaluated the therapeutic potential of a combination of C3aR and C5aR antagonists, and found that pharmacological blockade of C3aR/C5aR could effectively reduce GVHD severity while sparing GVL effect through persevering CD8 cytolytic activity.The current study reveals for the first time that escalation of autophagy in DCs is an effective therapeutic approach for the control of GVHD, and establishes and interaction between complement and autophagy in allo-HCT. We also provide a novel strategy of enhancing autophagy as a DC-based vaccination strategy for the control of GVHD after transplantation. [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

Exploring the Cord Blood T Cell Compartment with Mass Cytometry Reveals the Existence of Memory CD4, CD8 and Regulatory T Cell Pools in the Fetal Period

It has been long perceived that cord blood (CB) T cells are exclusively composed of antigen-inexperienced ‘naïve’ T cells under Th2 trophic and/or Th1 suppressive conditions, and that this is important for the maintenance of tolerance during pregnancy. However, a recent study reported the existence of a small fraction of memory CD4+ T cells with inflammatory cytokine profile within the sterile CB environment. This is in contrast to the common dogma challenging the presence of inflammatory T cells in the CB environment. To produce a more in-depth picture of the T cell compartment in CB, we assembled a panel of 40 antibodies to characterize the phenotypic and functional complexity of CB T cells. We interrogated the immune landscape of 12 CB donors vs 12 healthy adult peripheral blood (PB) donors to obtain single-cell profiles of the T-cell compartment. We used t-SNE algorithm to visualize the high dimensional data and the nearest-neighbor based clustering algorithm, PhenoGraph, to identify the potential clusters in high dimensional space. We observed significant segregation between PB and CB T cells. As expected, the majority of CD4+ and CD8+ T cells in CB were composed of naïve cells, while PB CD4+ and CD8+ T cells were characterized by a dominantly memory T cell phenotype. Within the CB CD4+ T cell compartment, in addition to the CD127+CD25- naïve T cell subset, we observed two more populations, including CD127+CD25int memory T cells (median 1.92%; range 0.69%-4.14%) and CD127lowCD25hi regulatory T-cells (Tregs) (median 1.9%; range 1.36%-2.98%). Similarly, a small subset of memory T cells, defined as CD45RA-CCR7+/-CD95+ (median 3.23%; range:1.53%-7.45%) was present in the CD8 T cell compartment in CB.Each T-cell presents a diversity of surface phenotypes defined by distinct combinations of marker expression. Thus, we sought an overview of the similarities and differences between CB and PB T-cell subsets. Analysis of CB Tregs revealed a repertoire composed mainly of naïve and central memory subsets, the latter expressed CD95, a marker of activation and memory, suggesting the generation of memory Tregs during fetal life. Both CB and PB Tregs were characterized by expression of PD-1, CD39, TIGIT, ICOS, CD161, CCR4, DNAM-1, CD49f and CD26. Expression of TIGIT, PD-1, CD39, CD49f, ICOS and CCR4 was exclusively confined to the memory Treg subset. In contrast to PB Tregs, CB Tregs lacked CCR10 and CXCR5 expression, suggesting differential migratory properties for CB and PB Tregs. We next focused on the differences between the naïve and memory CD4+ T cell subsets in CB. Chemokine receptors can be used to classify T-cell subsets with distinct migratory capacities and effector function. Naïve CD4 T cells do not express chemokine receptors, while memory T cells express different combinations of chemokine receptors that give clues to their lineage commitment. We discovered CCR6, CCR4, CXCR3, CD161, DNAM-1, CD49f, KLRG1, Beta7, PD-1, and TIGIT as the set of combinatorial markers to identify the memory CD4+ T cell pool in CB. Notably, a significant proportion of memory CD4+ T cells in CB expressed CCR4, supporting the notion that the CB environment drives a Th2 rather than a Th1 or Th17 functional phenotype. Moreover, in CB, expression of CCR6, CXCR3 and CD161 was confined to the memory CD4 T cell pool, suggesting that Th1, Th2 and Th17 lineage commitment starts in the fetal period, although the exact mechanism leading to memory T cell formation is not known.Taken together, interrogation of the T cell compartment in CB and PB in high dimensional space reveals well-defined and distinct memory signatures. Acquisition of memory phenotype instructs expression of unique sets of markers for each memory subset and varies among CD4, CD8 and Treg. Our data indicate the presence of a seemingly full-blown immune response, resulting in the generation of committed memory T cells and changes in the immune landscape of CB, although the initiating factor for this is yet to be determined. Mass cytometry proves to be a valuable tool in the characterization and discovery of novel T cell subsets, even if present at low frequencies. Studies to track the differentiation and diversification of T cells in CB transplant recipients and to link the impact of the T cell repertoire on clinical outcomes are under way. DisclosuresNo relevant conflicts of interest to declare.

A Novel Role for AMP-Activated Protein Kinase (AMPK) in Controlling T Cell Sensitivity to IL-6

Allogeneic hematopoietic stem cell transplantation (alloHSCT) is a curative treatment for high-risk leukemia and many non-malignant hematologic disorders. However, the use of alloHSCT as a therapy remains limited by acute graft-versus-host disease (GVHD), where activated donor T cells attack and destroy host tissues in the skin, gastrointestinal tract, and liver. We have previously shown that alloreactive T cells increase phosphorylation of the intracellular energy sensor AMP-activated protein kinase (AMPK) as early as day 3 post-transplant (levels 8-fold higher in alloreactive T cells compared to naive or syngeneic controls (p=0.0003)) and donor T cells lacking AMPK (AMPK KO) cause significantly less GVHD in both major- and minor-histocompatibility mismatch models of GVHD. At the same time, AMPK KO T cells equivalently clear leukemia cells and extend recipient survival in leukemia models with high tumor burden. Transplantation of cells lacking AMPK lowers the number of donor T cells recovered on day 7 post-transplant (3.15 +/- 0.49x106 versus1.87 +/- 0.53x106, p=0.0006, wildtype (wt) versus AMPKKO respectively) but interestingly, increases both the percentage and total number of regulatory T cells (Treg) (0.85 +/- 0.32x104 vs. 1.69 +/- 0.34x104, wt vs. KO, p=0.004).To understand these findings mechanistically, we sought to study the role of AMPK in donor Treg expansion and stabilization post-alloHSCT. Canonically, interleukin-2 (IL-2) signaling, through phosphorylation of Stat5, promotes Treg generation and stability, while inflammatory signals (e.g. IL-6 signaling through Stat3) are known to decrease Treg stability post-transplant. Studies testing IL-2 sensitivity in KO cells, or the degree of Stat5 phosphorylation post-transplant, were unrevealing. However, AMPK KO Tregs significantly decrease their sensitivity to IL-6, with a 50% reduction in phosphorylated-Stat3 levels following intermediate levels of cytokine stimulation (Figure 1A). To demonstrate the functional consequences of this difference in cytokine sensitivity, we exposed in vitro generated Treg to increasing concentrations of IL-6. As expected, the percentage of wt FoxP3+ cells decreased sharply with increasing IL-6 concentrations (decreasing from 50% to 14%), while AMPK KO Tregs were minimally affected over this dose range (47% versus 42%; Figure 1B, p<0.02).To determine if increased Treg stability was the predominant reason for improvements in GVHD seen with AMPK KO cells, CD25+ cells were removed from the donor inoculum of AMPK KO or wt mice by magnetic selection (to eliminate >90% of Treg), and then either CD25-replete or CD25-depleted sets of cells were transplanted into B6xDBA2 F1 recipients in a major MHC mismatch model of GVHD. Despite a decrease in AMPK KO Treg numbers on day 7 to levels commiserate with wt donors (Figure 2A), elimination of AMPK KO Treg had only a modest effect on GVHD severity (Figure 2B), implicating a substantial role for AMPK in the non-Treg compartment.To explore the role of AMPK in non-Tregs further, we investigated the sensitivity of unmanipulated wt and AMPK KO T cells to IL-6 stimulation. Similar to FoxP3+ cells, both naïve CD4 and CD8 T cells lacking AMPK experienced lower levels of Stat3 phosphorylation in response to graded concentrations of IL-6 (Figure 3A). Furthermore, if IL-6 was added to a 4-day culture with anti-CD3 stimulation, the number of wt T cells recovered after 96 hours increased >2.2-fold. In contrast, AMPK KO cells experienced minimal changes in T cell number over a wide range of IL-6 concentrations (Figure 3B).In conclusion, we define in these studies a novel role for AMPK in controlling donor T cell sensitivity to IL-6, both at the level of Stat3 phosphorylation, and in terms of functional consequences. Not only does this striking result elegantly explain our previous observation of increased Treg percentages, and decreased donor T cell numbers, following transplantation of AMPK KO cells, it continues to make the case that inhibition of AMPK represents an attractive clinical target for the amelioration of GVHD. [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

The Curcumin Analog GO-Y030 Controls the Generation and Stability of Regulatory T Cells.

Regulatory T cells (Tregs) play a crucial role in preventing antitumor immune responses in cancer tissues. Cancer tissues produce large amounts of transforming growth factor beta (TGF-β), which promotes the generation of Foxp3+ Tregs from naïve CD4+ T cells in the local tumor microenvironment. TGF-β activates nuclear factor kappa B (NF-κB)/p300 and SMAD signaling, which increases the number of acetylated histones at the Foxp3 locus and induces Foxp3 gene expression. TGF-β also helps stabilize Foxp3 expression. The curcumin analog and antitumor agent, GO-Y030, prevented the TGF-β-induced generation of Tregs by preventing p300 from accelerating NF-κB-induced Foxp3 expression. Moreover, the addition of GO-Y030 resulted in a significant reduction in the number of acetylated histones at the Foxp3 promoter and at the conserved noncoding sequence 1 regions that are generated in response to TGF-β. In vivo tumor models demonstrated that GO-Y030-treatment prevented tumor growth and reduced the Foxp3+ Tregs population in tumor-infiltrating lymphocytes. Therefore, GO-Y030 exerts a potent anticancer effect by controlling Treg generation and stability.

Intestinal cDC1 drive cross-tolerance to epithelial-derived antigen via induction of FoxP3+CD8+ Tregs.

Although CD8+ T cell tolerance to tissue-specific antigen (TSA) is essential for host homeostasis, the mechanisms underlying peripheral cross-tolerance and whether they may differ between tissue sites remain to be fully elucidated. Here, we demonstrate that peripheral cross-tolerance to intestinal epithelial cell (IEC)-derived antigen involves the generation and suppressive function of FoxP3+CD8+ T cells. FoxP3+CD8+ Treg generation was dependent on intestinal cDC1, whose absence led to a break of tolerance and epithelial destruction. Mechanistically, intestinal cDC1-derived PD-L1, TGFβ, and retinoic acid contributed to the generation of gut-tropic CCR9+CD103+FoxP3+CD8+ Tregs Last, CD103-deficient CD8+ T cells lacked tolerogenic activity in vivo, indicating a role for CD103 in FoxP3+CD8+ Treg function. Our results describe a role for FoxP3+CD8+ Tregs in cross-tolerance in the intestine for which development requires intestinal cDC1.

Modulation of Intestinal ILC3 for the Treatment of Type 1 Diabetes.

Gut-associated lymphoid tissue (GALT) is crucial for the maintenance of the intestinal homeostasis, but it is also the potential site of the activation of autoreactive cells and initiation/propagation of autoimmune diseases in the gut and in the distant organs. Type 3 innate lymphoid cells (ILC3) residing in the GALT integrate signals from food ingredients and gut microbiota metabolites in order to control local immunoreactivity. Notably, ILC3 secrete IL-17 and GM-CSF that activate immune cells in combating potentially pathogenic microorganisms. ILC3 also produce IL-22 that potentiates the strength and integrity of epithelial tight junctions, production of mucus and antimicrobial peptides thus enabling the proper function of the intestinal barrier. The newly discovered function of small intestine ILC3 is the secretion of IL-2 and the promotion of regulatory T cell (Treg) generation and function. Since the intestinal barrier dysfunction, together with the reduction in small intestine ILC3 and Treg numbers are associated with the pathogenesis of type 1 diabetes (T1D), the focus of this article is intestinal ILC3 modulation for the therapy of T1D. Of particular interest is free fatty acids receptor 2 (FFAR2), predominantly expressed on intestinal ILC3, that can be stimulated by available selective synthetic agonists. Thus, we propose that FFAR2-based interventions by boosting ILC3 beneficial functions may attenuate autoimmune response against pancreatic β cells during T1D. Also, it is our opinion that treatments based on ILC3 stimulation by functional foods can be used as prophylaxis in individuals that are genetically predisposed to develop T1D.

Mesenchymal Stem Cell Protects Injured Renal Tubular Epithelial Cells by Regulating mTOR-Mediated Th17/Treg Axis

The increase in T helper 17 cell (Th17)-mediated pro-inflammatory response and decrease in regulatory T cell (Treg)-mediated anti-inflammatory effect aggravate renal tubular epithelial cell (RTEC) injury. However, increasing evidence indicated that mesenchymal stem cell (MSC) possessed the ability to control the imbalance between Th17 and Treg. Given that Th17 and Treg are derived from a common CD4+ T cell precursor, we summarize the current knowledge of MSC-mediated inhibition of the mammalian target of rapamycin (mTOR), which is a master regulator of CD4+ T cell polarization. During CD4+ T cell differentiation, mTOR signaling mediates Th17 and Treg differentiation via hypoxia-inducible factor-1α (HIF-1α)-dependent metabolic regulation and signaling pathway, as well as mTOR-mediated phosphorylation of signal transducer and activator of transcription (STAT) 3 and 5. Through interfering with mTOR signaling, MSC restrains CD4+ T cell differentiation into Th17, but in turn promotes Treg generation. Thus, this review indicates that MSC-mediated Th17-to-Treg polarization is expected to act as new immunotherapy for kidney injury.

Clinical and Basic Research Progress on Treg-Induced Immune Tolerance in Liver Transplantation.

Rejection after organ transplantation is a cause of graft failure. Effectively reducing rejection and inducing tolerance is a challenge in the field of transplantation immunology. The liver, as an immunologically privileged organ, has high rates of spontaneous and operational tolerance after transplantation, allowing it to maintain its normal function for long periods. Although modern immunosuppression regimens have serious toxicity and side effects, it is very risky to discontinue immunosuppression regimens blindly. A more effective treatment to induce immune tolerance is the most sought-after goal in transplant medicine. Tregs have been shown to play a pivotal role in the regulation of immune balance, and infusion of Tregs can also effectively prevent rejection and cure autoimmune diseases without significant side effects. Given the immune characteristics of the liver, the correct use of Tregs can more effectively induce the occurrence of operational tolerance for liver transplants than for other organ transplants. This review mainly summarizes the latest research advances regarding the characteristics of the hepatic immune microenvironment, operational tolerance, Treg generation in vitro, and the application of Tregs in liver transplantation. It is hoped that this review will provide a deeper understanding of Tregs as the most effective treatment to induce and maintain operational tolerance after liver transplantation.

IL-21 Is an Accomplice of PD-L1 in the Induction of PD-1-Dependent Treg Generation in Head and Neck Cancer.

Regulatory T cells (Tregs) are immunosuppressive cells involved in antitumor immunity. However, the regulation of Treg generation by inflammation in the tumor microenvironment has not been carefully investigated. Here, we demonstrated that IL-21-polarized inflammation was enriched in the tumor microenvironment in head and neck squamous cell carcinoma (HNSCC) and that IL-21 could promote PD-L1-induced Treg generation in a PD-1-dependent manner. Moreover, generated Tregs showed a greater ability to suppress the proliferation of tumor-associated antigen (TAA)-specific T cells than naturally occurring Tregs. Importantly, an anti-PD-1 antibody could inhibit only Treg expansion induced by clinical tumor explants with high expression of IL-21/PD-L1. In addition, neutralizing IL-21 could enhance the anti-PD-1 antibody-mediated inhibitory effect on Treg expansion. Furthermore, simultaneous high expression of IL-21 and PD-L1 was associated with more Treg infiltrates and predicted reduced overall and disease-free survival in patients with HNSCC. These findings indicate that IL-21 in the tumor microenvironment may promote PD-L1-induced, Treg-mediated immune escape in a PD-1-dependent manner and that an IL-21 neutralization strategy may enhance PD-1 blockade-based antitumor immunotherapy by targeting Treg-mediated immune evasion in patients with high expression of IL-21 and PD-L1.

MHCII-mediated antigen presentation by thymic stromal cells is required to enforce central T-cell tolerance

Abstract Central T-cell tolerance relies on elimination of self-reactive CD4+ T-cell clones in the thymus by either deletion or conversion to regulatory T cells (tTregs). Developing thymocytes are selected by exposure to tissue-specific antigens (TSAs) expressed by thymic medullary epithelial cells (mTECs) under the control of Autoimmune Regulator (Aire). TSA-derived peptides-MHCII complexes can be presented either directly by mTECs or indirectly by thymic DCs. Dissecting the contributions of these antigen presenting cell (APC) subsets to thymic tolerance has been hindered by the lack of appropriate genetic tools to selectively target presentation by mTECs. To address this, we created a mouse model in which MHCII can be inducibly ablated in Aire-expressing mTECs (iAire-CreERT2;MHCIIfl/fl). We show that treatment of these mice with tamoxifen leads to a complete loss of MHCII expression by Aire+ and post-Aire mTECs without affecting other thymic APCs or perturbing thymic homeostasis. In a TCR-restricted mouse model of negative selection, ablation of MHCII on mTECs led to a failure to delete self-reactive T cells, allowing escape and activation in the periphery. Surprisingly, we also found a defect in conversion of self-reactive CD4+ T cells to FoxP3+ tTregs. Similarly, in the diverse repertoire, loss of direct antigen presentation by mTECs resulted in tTreg reduction. In contrast, using CD11c-Cre;MHCIIfl/fl mice, in which MHCII is absent on thymic DCs but not mTECs, we found no disruption to negative selection or Treg generation. In sum, our data support a distinct and non-redundant role for direct antigen presentation by mTECs in shaping thymic T cell selection.

B7-CD28 co-stimulation enforces central tolerance by thymic clonal deletion and Treg cell generation through distinct mechanisms

Abstract To establish central T cell tolerance in the thymus, thymocytes expressing TCR strongly reactive to self-Ag-MHC complex are eliminated from the conventional T cell (Tconv) repertoire by two distinct processes, clonal deletion or clonal diversion to non-conventional T cell lineages such as Foxp3+ regulatory T (Treg) cells. We analyzed the requirements for B7-CD28 co-stimulation for thymic clonal deletion and Treg cell generation of endogenous tissue-restricted-antigen (TRA)-specific thymocytes. We found that: 1) both clonal deletion and Treg cell generation of TRA-specific thymocytes were B7-CD28-dependent, and that clonal deletion had a greater effect than Treg diversion in eliminating TRA-specific T cells from the Tconv repertoire; 2) B7-expressing APC requirements differed for clonal deletion and Treg generation; and 3) although B7-CD28 mediated both clonal deletion and Treg cell generation, CD28 cytoplasmic domain requirements for these two processes were different. These results indicate that qualitatively distinct CD28 signaling determines fates of strongly self-reactive thymocytes. To further characterize the CD28 signaling pathways involved in clonal deletion and Treg cell generation, single cell transcriptomic analyses of TRA-specific thymocyte are underway.

Juglone regulates gut microbiota and Th17/Treg balance in DSS-induced ulcerative colitis

Juglone, mainly isolates from the green walnut husks of Juglans mandshurica, exhibits anti-cancer and anti-inflammaroty activities. But its protection on ulcerative colitis (UC) has never been explored. In this study, we first evaluated whether juglone ameliorated UC, and investigated its effects on gut microbiota and Th17/Treg balance in DSS-induced UC mice model. The model was established by administrating 2.7% DSS for seven days. Juglone was given daily by gavage for ten days, once a day. The disease activity index (DAI) decrease and pathological characteristics improvement demonstrated that the UC in mice was alleviated by juglone. Juglone treatment significantly inhibited the protein levels of IL-6, TNF-α and IL-1β, improved the protein expression of IL-10. In addition, juglone altered microbial diversity and gut microbiota composition, including the enhancement of the ratio of Firmicutes to Bacteroidota and the abundance of Actinobacteriota, and decrease of the abundance of Verrucomicrobiota. Juglone treatment also inhibited the protein expressions of IL-6, STAT3 and RORγt, meanwhile improved the protein level of FOXP3. Furthermore, juglone inhibited Th17 development and increased Treg generation, beneficial to Th17/Treg balance. Together, we herein provided the first evidence to support that juglone, especially the high dose, possibly protected mice against UC by modulating gut microbiota and restoring Th17/Treg homeostasis.

Preventing alloimmune rejection using circular RNA FSCN1-silenced dendritic cells in heart transplantation

While heart transplantation is used as a standard treatment for heart failure, transplant rejection continues to pose a challenge. Recent evidence has shown that circular RNA (circRNA) is a new type of gene regulator in cell development. Our aim was to demonstrate that treatment with tolerogenic dendritic cells (Tol-DCs) generated by circular RNA FSCN1 (circFSCN1) silencing could prevent alloimmune rejection and prolong heart graft survival in heart transplantation. Bone marrow-derived DCs were transfected with circFSCN1 siRNA in vitro. The circFSCN1 level was measured by qRT-PCR. DC maturation was determined by flow cytometry. Mixed lymphocyte reactions (MLRs) were conducted to assess the function of DCs to activate T cells and to generate regulatory T cells (Tregs). In situ RNA hybridization and fluorescent microscopy were performed to detect the distribution of circFSCN1 in DCs. A heterotopic allogeneic murine heart transplantation was conducted where recipients were pre-treated with donor derived circFSCN1-silenced Tol-DCs. Heartbeat was monitored to assess immune rejection. Exonic circFSCN1 was highly expressed in the cytoplasm of mature DCs. Knockdown of circFSCN1 using siRNA arrested DCs at an immature state, impaired DC's ability to activate T cells and enhanced Treg generation. Treatment with circFSCN1-silenced Tol-DCs prevented alloimmune rejection, prolonged allograft survival, reduced fibrosis, and induced Tregs in vivo. Knockdown of circFSCN1 induces Tol-DCs and treatment with these Tol-DCs prevents alloimmune rejection and prolongs allograft survival. This is a promising therapeutic target to combat transplant rejection in heart transplantation and increases our understanding of circRNA in the immune system.