IL-10 is required for regulatory T cells to mediate tolerance to alloantigens in vivo

Galectin-1 is associated with hematopoietic cell engraftment in murine MHC-mismatched allotransplantation

Haploidentical hematopoietic cell transplantation (haplo-HCT) is associated with an increased risk of allograft rejection. Here, we employed a major histocompatibility complex (MHC)-mismatched allogeneic HCT (allo-HCT) murine model to better understand the role of Gal-1 in immune tolerance. Transplanted mice were classified into either rejected or engrafted based on donor chimerism levels. We noted significantly higher frequencies of CD4+ T cells, CD8+ T cells, natural killer cells, IFN-γ and TNF-α producing CD4+ T cells, and IFN-γ producing dendritic cells and macrophages in rejected mice. Conversely, we found significantly increased frequencies of regulatory T cells (Tregs), predominantly Helios+, IL-10-producing CD4+ T cells, type 1 regulatory (Tr1) cells, and the proportion of Tr1+Gal-1+ cells in engrafted mice. Further, Gal-1 specific blockade in Tregs reduced suppression of effector T cells in engrafted mice. Lastly, effector T cells from engrafted mice were more prone to undergo apoptosis. Collectively, we have shown that Gal-1 may favor HSC engraftment in an MHC-mismatched murine model. Our results demonstrate that Gal-1-expressing Tregs, especially at earlier time points post-transplant, are associated with inducing immune tolerance and stable mixed chimerism after HCT.

IL-10 Is Critical for Regulation of Cytotoxic CD4+NKG7+ T Cells in Lung Allograft Rejection but Is Not Required for Allograft Acceptance

Lung transplant remains the primary therapeutic option for patients with end-stage lung disease, but long-term survival rates remain suboptimal compared with other solid organ transplants. Acute cellular rejection (ACR) is a significant challenge in lung transplant recipients, with T cell-mediated mechanisms playing a major role. IL-10 is known for its immunoregulatory function, although its specific role in lung allograft rejection remains unclear. Using the mouse orthotopic lung transplant model, we investigated the role of IL-10 in regulating alloeffector T cell responses. Unexpectedly, we found that IL-10 was not required for early costimulation blockade-induced allograft acceptance. However, IL-10 deficiency or blockade resulted in increased CD4+ T cell numbers, proliferation, graft infiltration, and alloeffector responses. In the absence of IL-10, CD4+ T cell responses predominated over CD8 responses during ACR in contrast to wild-type mice. Type 1 immunity (IFN-γ) responses along with elevated CD4+NKG7+ and CD4+CD107a+ responses predominated during ACR, highlighting a critical regulatory role for IL-10 in modulating CD4+ T cell alloimmune responses. We further demonstrated increased colocalization of NKG7 and CD107a in CD4+ T cells from IL-10-deficient allografts, suggesting coordination in cytotoxic activity. Together, our findings highlight a critical role for IL-10 in regulation of cytotoxic CD4+NKG7+ T cells, an effector population that needs further investigation to elucidate their role in lung allograft rejection.

Polyclonally Derived Alloantigen-Specific T Regulatory Cells Exhibit Target-Specific Suppression and Capture MHC Class II from Dendritic Cells

Foxp3+ T regulatory (Treg) cells prevent allograft rejection and graft-versus-host disease. Although polyclonal Tregs have been used both in animal models and in humans, the fine specificity of their suppressive function is poorly defined. We have generated mouse recipient-derived alloantigen-specific Tregs in vitro and explored the fine specificity of their suppressive function and their mechanism of action in vitro and in vivo. In vitro, when alloantigen and peptide Ag were both presented on the same dendritic cell, both responses were suppressed by iTregs specific either for the alloantigen or for the peptide Ag. In vivo, iTreg suppression was limited to the cognate Ag, and no bystander suppression was observed when both allo-antigen and peptide Ag were present on the same dendritic cell. In vitro, alloantigen-specific Tregs captured cognate MHC but failed to capture noncognate MHC. Our results demonstrate that a polyclonal population of iTregs generated from naive T cells can mediate highly specific function in vivo and support the view that Treg therapy, even with unselected polyclonal populations, is likely to be target antigen-specific and that bystander responses to self-antigens or to infectious agents are unlikely.

T cell responsiveness to IL-10 defines the immunomodulatory effect of costimulation blockade via anti-CD154 and impacts transplant survival

Costimulation blockade (CoB)-based immunotherapy is a promising alternative to immunosuppression for transplant recipients; however, the current limited understanding of the factors that impact its efficacy restrains its clinical applicability. In this context, pro- and anti-inflammatory cytokines are being recognized as having an impact on T cell activation beyond effector differentiation. This study aims at elucidating the impact of direct IL-10 signaling in T cells on CoB outcomes. We used a full-mismatch skin transplantation model where recipients had a T cell-restricted expression of a dominant negative IL-10 receptor (10R-DN), alongside anti-CD154 as CoB therapy. Unlike wild-type recipients, 10R-DN mice failed to benefit from CoB. This accelerated graft rejection correlated with increased accumulation of T cells producing TNF-α, IFN-γ, and IL-17. In vitro experiments indicated that while lack of IL-10 signaling did not change the ability of anti-CD154 to modulate alloreactive T cell proliferation, the absence of this pathway heightened TH1 effector cell differentiation. Furthermore, deficiency of IL-10 signaling in T cells impaired Treg induction, a hallmark of anti-CD154 therapy. Overall, these findings unveil an important and novel role of IL-10 signaling in T cells that defines the success of CoB therapies and identifies a target pathway for obtaining robust immunoregulation.

Unlocking Transplant Tolerance with Biomaterials

For patients suffering from organ failure due to injury or autoimmune disease, allogeneic organ transplantation with chronic immunosuppression is considered the god standard in terms of clinical treatment. However, the true "holy grail" of transplant immunology is operational tolerance, in which the recipient exhibits a sustained lack of alloreactivity toward unencountered antigen presented by the donor graft. This outcome is resultant from critical changes to the phenotype and genotype of the immune repertoire predicated by the activation of specific signaling pathways responsive to soluble and mechanosensitive cues. Biomaterials have emerged as a medium for interfacing with and reprogramming these endogenous pathways toward tolerance in precise, minimally invasive, and spatiotemporally defined manners. By viewing seminal and contemporary breakthroughs in transplant tolerance induction through the lens of biomaterials-mediated immunomodulation strategies-which include intrinsic material immunogenicity, the depot effect, graft coatings, induction and delivery of tolerogenic immune cells, biomimicry of tolerogenic immune cells, and in situ reprogramming-this review emphasizes the stunning diversity of approaches in the field and spotlights exciting future directions for research to come.

A humanized IL-2 mutein expands Tregs and prolongs transplant survival in preclinical models

Long-term organ transplant survival remains suboptimal, and life-long immunosuppression predisposes transplant recipients to an increased risk of infection, malignancy, and kidney toxicity. Promoting the regulatory arm of the immune system by expanding Tregs may allow immunosuppression minimization and improve long-term graft outcomes. While low-dose IL-2 treatment can expand Tregs, it has a short half-life and off-target expansion of NK and effector T cells, limiting its clinical applicability. Here, we designed a humanized mutein IL-2 with high Treg selectivity and a prolonged half-life due to the fusion of an Fc domain, which we termed mIL-2. We showed selective and sustainable Treg expansion by mIL-2 in 2 murine models of skin transplantation. This expansion led to donor-specific tolerance through robust increases in polyclonal and antigen-specific Tregs, along with enhanced Treg-suppressive function. We also showed that Treg expansion by mIL-2 could overcome the failure of calcineurin inhibitors or costimulation blockade to prolong the survival of major-mismatched skin grafts. Validating its translational potential, mIL-2 induced a selective and sustainable in vivo Treg expansion in cynomolgus monkeys and showed selectivity for human Tregs in vitro and in a humanized mouse model. This work demonstrated that mIL-2 can enhance immune regulation and promote long-term allograft survival, potentially minimizing immunosuppression.

Multiple infusions of ex vivo-expanded regulatory T cells promote CD163+ myeloid cells and kidney allograft survival in non-lymphodepleted non-human primates

Clinical verification of adoptively transferred regulatory T cell (Treg) efficacy in transplantation remains challenging. Here, we examined the influence of autologous ex vivo-expanded polyclonal Tregs on kidney graft survival in a clinically relevant non-human primate model. Peripheral blood Tregs were isolated and expanded using artificial antigen presenting cells. Immunosuppression was comprised of tapered tacrolimus and CTLA4 immunoglobulin, in five animals each without or with Treg infusions. Escalating Treg doses were administered 6, 10, 13, 16, 20, 23, 27 and 30 days after transplant. Infused Tregs were monitored for Treg signature, anti-apoptotic (Bcl-2) and proliferation (Ki67) marker expression. Treg infusions prolonged median graft survival time significantly from 35 to 70 days. Treg marker (Ki67 and Bcl-2) expression by infused Tregs diminished after their infusion but remained comparable to that of circulating native Tregs. No major changes in circulating donor-reactive T cell responses or total Treg percentages, or in graft-infiltrating T cell subsets were observed with Treg infusion. However, Treg infusion was associated with significant increases in CD163 expression by circulating HLA-DR+ myeloid cells and elevated levels of circulating soluble CD163. Further, graft-infiltrating CD163+ cells were increased with Treg infusion. Thus, multiple Treg infusions were associated with M2-like myeloid cell enhancement that may mediate immunomodulatory, anti-inflammatory and graft reparative effects.

Monitoring regulatory T cells as a prognostic marker in lung transplantation

Lung transplantation is the major surgical procedure, which restores normal lung functioning and provides years of life for patients suffering from major lung diseases. Lung transplant recipients are at high risk of primary graft dysfunction, and chronic lung allograft dysfunction (CLAD) in the form of bronchiolitis obliterative syndrome (BOS). Regulatory T cell (Treg) suppresses effector cells and clinical studies have demonstrated that Treg levels are altered in transplanted lung during BOS progression as compared to normal lung. Here, we discuss levels of Tregs/FOXP3 gene expression as a crucial prognostic biomarker of lung functions during CLAD progression in clinical lung transplant recipients. The review will also discuss Treg mediated immune tolerance, tissue repair, and therapeutic strategies for achieving in-vivo Treg expansion, which will be a potential therapeutic option to reduce inflammation-mediated graft injuries, taper the toxic side effects of ongoing immunosuppressants, and improve lung transplant survival rates.

Sex differences in innate and adaptive immunity impact fetal, placental, and maternal health†

The differences between males and females begin shortly after birth, continue throughout prenatal development, and eventually extend into childhood and adult life. Male embryos and fetuses prioritize proliferation and growth, often at the expense of the fetoplacental energy reserves. This singular focus on growth over adaptability leaves male fetuses and neonates vulnerable to adverse outcomes during pregnancy and birth and can have lasting impacts throughout life. Beyond this prioritization of growth, male placentas and fetuses also respond to infection and inflammation differently than female counterparts. Pregnancies carrying female fetuses have a more regulatory immune response, whereas pregnancies carrying male fetuses have a stronger inflammatory response. These differences can be seen as early as the innate immune response with differences in cytokine and chemokine signaling. The sexual dimorphism in immunity then continues into the adaptive immune response with differences in T-cell biology and antibody production and transfer. As it appears that these sex-specific differences are amplified in pathologic pregnancies, it stands to reason that differences in the placental, fetal, and maternal immune responses in pregnancy contribute to increased male perinatal morbidity and mortality. In this review, we will describe the genetic and hormonal contributions to the sexual dimorphism of fetal and placental immunity. We will also discuss current research efforts to describe the sex-specific differences of the maternal-fetal interface and how it impacts fetal and maternal health.

Regulatory T cells in autoimmune kidney diseases and transplantation

Regulatory T (Treg) cells that express the transcription factor forkhead box protein P3 (FOXP3) are naturally present in the immune system and have roles in the maintenance of immunological self-tolerance and immune system and tissue homeostasis. Treg cells suppress T cell activation, expansion and effector functions by various mechanisms, particularly by controlling the functions of antigen-presenting cells. They can also contribute to tissue repair by suppressing inflammation and facilitating tissue regeneration, for example, via the production of growth factors and the promotion of stem cell differentiation and proliferation. Monogenic anomalies of Treg cells and genetic variations of Treg cell functional molecules can cause or predispose patients to the development of autoimmune diseases and other inflammatory disorders, including kidney diseases. Treg cells can potentially be utilized or targeted to treat immunological diseases and establish transplantation tolerance, for example, by expanding natural Treg cells in vivo using IL-2 or small molecules or by expanding them in vitro for adoptive Treg cell therapy. Efforts are also being made to convert antigen-specific conventional T cells into Treg cells and to generate chimeric antigen receptor Treg cells from natural Treg cells for adoptive Treg cell therapies with the aim of achieving antigen-specific immune suppression and tolerance in the clinic.

The mast cell: A Janus in kidney transplants

Mast cells (MCs) are innate immune cells with a versatile set of functionalities, enabling them to orchestrate immune responses in various ways. Aside from their known role in allergy, they also partake in both allograft tolerance and rejection through interaction with regulatory T cells, effector T cells, B cells and degranulation of cytokines and other mediators. MC mediators have both pro- and anti-inflammatory actions, but overall lean towards pro-fibrotic pathways. Paradoxically, they are also seen as having potential protective effects in tissue remodeling post-injury. This manuscript elaborates on current knowledge of the functional diversity of mast cells in kidney transplants, combining theory and practice into a MC model stipulating both protective and harmful capabilities in the kidney transplant setting.

Into the multi-omics era: Progress of T cells profiling in the context of solid organ transplantation

T cells are the common type of lymphocyte to mediate allograft rejection, remaining long-term allograft survival impeditive. However, the heterogeneity of T cells, in terms of differentiation and activation status, the effector function, and highly diverse T cell receptors (TCRs) have thus precluded us from tracking these T cells and thereby comprehending their fate in recipients due to the limitations of traditional detection approaches. Recently, with the widespread development of single-cell techniques, the identification and characterization of T cells have been performed at single-cell resolution, which has contributed to a deeper comprehension of T cell heterogeneity by relevant detections in a single cell - such as gene expression, DNA methylation, chromatin accessibility, surface proteins, and TCR. Although these approaches can provide valuable insights into an individual cell independently, a comprehensive understanding can be obtained when applied joint analysis. Multi-omics techniques have been implemented in characterizing T cells in health and disease, including transplantation. This review focuses on the thesis, challenges, and advances in these technologies and highlights their application to the study of alloreactive T cells to improve the understanding of T cell heterogeneity in solid organ transplantation.

Foxp3+ regulatory T cell therapy for tolerance in autoimmunity and solid organ transplantation

Regulatory T cells (Tregs) are critical for tolerance in humans. The exact mechanisms by which the loss of peripheral tolerance leads to the development of autoimmunity and the specific role Tregs play in allograft tolerance are not fully understood; however, this population of T cells presents a unique opportunity in the development of targeted therapeutics. In this review, we discuss the potential roles of Foxp3+ Tregs in the development of tolerance in transplantation and autoimmunity, and the available data regarding their use as a treatment modality.

Regulatory T cells in rheumatoid arthritis: functions, development, regulation, and therapeutic potential

Rheumatoid arthritis (RA) is an autoimmune disease that mainly affects the joints but also leads to systemic inflammation. Auto-reactivity and dysregulation of self-tolerance are thought to play a vital role in disease onset. In the pathogenesis of autoimmune diseases, disturbed immunosuppressive properties of regulatory T cells contribute to the dysregulation of immune homeostasis. In RA patients, the functions of Treg cells and their frequency are reduced. Therefore, focusing on the re-establishment of self-tolerance by increasing Treg cell frequencies and preventing a loss of function is a promising strategy for the treatment of RA. This approach could be especially beneficial for those patients who do not respond well to current therapies. In this review, we summarize and discuss the current knowledge about the function, differentiation and regulation of Treg cells in RA patients and in animal models of autoimmune arthritis. In addition, we highlight the therapeutic potential as well as the challenges of Treg cell targeting treatment strategies.

Role of HLA-I Structural Variants and the Polyreactive Antibodies They Generate in Immune Homeostasis

Cell-surface HLA-I molecules consisting of β2-microglobulin (β2m) associated heavy chains (HCs), referred to as Face-1, primarily present peptides to CD8+ T-cells. HCs consist of three α-domains, with selected amino acid sequences shared by all alleles of all six isoforms. The cell-surface HLA undergoes changes upon activation by pathological conditions with the expression of β2m-free HCs (Face-2) resulting in exposure of β2m-masked sequences shared by almost all alleles and the generation of HLA-polyreactive antibodies (Abs) against them. Face-2 may homodimerize or heterodimerize with the same (Face-3) or different alleles (Face-4) preventing exposure of shared epitopes. Non-allo immunized males naturally carry HLA-polyreactive Abs. The therapeutic intravenous immunoglobulin (IVIg) purified from plasma of thousands of donors contains HLA-polyreactive Abs, admixed with non-HLA Abs. Purified HLA-polyreactive monoclonal Abs (TFL-006/007) generated in mice after immunizing with Face-2 are documented to be immunoregulatory by suppressing or activating different human lymphocytes, much better than IVIg. Our objectives are (a) to elucidate the complexity of the HLA-I structural variants, and their Abs that bind to both shared and uncommon epitopes on different variants, and (b) to examine the roles of those Abs against HLA-variants in maintaining immune homeostasis. These may enable the development of personalized therapeutic strategies for various pathological conditions.

Roles of Mast Cells in Cutaneous Diseases

Mast cells are present in all vascularized tissues of the body. They are especially abundant in tissues that are in frequent contact with the surrounding environment and act as potential sources of inflammatory and/or regulatory mediators during development of various infections and diseases. Mature mast cells’ cytoplasm contains numerous granules that store a variety of chemical mediators, cytokines, proteoglycans, and proteases. Mast cells are activated via various cell surface receptors, including FcϵRI, toll-like receptors (TLR), Mas-related G-protein-coupled receptor X2 (MRGPRX2), and cytokine receptors. IgE-mediated mast cell activation results in release of histamine and other contents of their granules into the extracellular environment, contributing to host defense against pathogens. TLRs, play a crucial role in host defense against various types of pathogens by recognizing pathogen-associated molecular patterns. On the other hand, excessive/inappropriate mast cell activation can cause various disorders. Here, we review the published literature regarding the known and potential inflammatory and regulatory roles of mast cells in cutaneous inflammation, including atopic dermatitis, psoriasis, and contact dermatitis GVHD, as well as in host defense against pathogens.

PD-1 inhibitor induces myocarditis by reducing regulatory T cells, activating inflammatory responses, promoting myocardial apoptosis and autophagy

The present study aimed to explore the pathogenesis of autoimmune myocarditis induced by PD-1 inhibitors and their potential therapeutic targets. Mouse models of autoimmune myocarditis induced by PD-1 inhibitor in mouse models of polymyositis were established. The expression level of PD-1 and regulatory T cells (Tregs), CD4, CD8 + T cells, inflammation, apoptosis and autophagy-related factors, including IL-6, TGF-β, AMA-M2, Fas/FasL, LC3 and p62 were detected in peripheral blood, muscle or myocardium of mice in each group, using ELISA, RT-PCR, Western Blot and immunofluorescence. In addition, HE and TUNEL staining and ultrastructural scanning were performed on the myocardium of mice in each group. Results showed that the expression level of PD-1 in the two myositis groups was significantly lower than that in the control group, and the level of PD-1 was lower in the myocarditis group than that in the polymyositis group. In the myocardium, TGF-β, p62, and Tregs proportion showed the same expression level trend as PD-1, while CD8, IL-6, IL-10 and LC3 showed the opposite trend. Levels of Fas/FasL were significantly higher in both myositis groups, but were slightly lower in the myocarditis group, as was AMA-M2. Inflammation, apoptosis, and autophagy were observed in both myositis groups, but were more severe in the myocarditis group. In summary, the decreased expression level of PD-1 leads to decreased Tregs level in the myocardium, aggravated inflammatory response, apoptosis and autophagy, which may be the pathological mechanism of myocarditis induced by PD-1 inhibitors.

Cytolytic CD4+ and CD8+ Regulatory T-Cells and Implications for Developing Immunotherapies to Combat Graft-Versus-Host Disease

Regulatory T-cells (Treg) are critical for the maintenance of immune homeostasis and tolerance induction. While the immunosuppressive mechanisms of Treg have been extensively investigated for decades, the mechanisms responsible for Treg cytotoxicity and their therapeutic potential in regulating immune responses have been incompletely explored and exploited. Conventional cytotoxic T effector cells (Teffs) are known to be important for adaptive immune responses, particularly in the settings of viral infections and cancer. CD4+ and CD8+ Treg subsets may also share similar cytotoxic properties with conventional Teffs. Cytotoxic effector Treg (cyTreg) are a heterogeneous population in the periphery that retain the capacity to suppress T-cell proliferation and activation, induce cellular apoptosis, and migrate to tissues to ensure immune homeostasis. The latter can occur through several cytolytic mechanisms, including the Granzyme/Perforin and Fas/FasL signaling pathways. This review focuses on the current knowledge and recent advances in our understanding of cyTreg and their potential application in the treatment of human disease, particularly Graft-versus-Host Disease (GVHD).

Study Design: HLA-A*02-Chimeric Antigen Receptor Regulatory T Cells in Renal Transplantation

Introduction

Cell therapy with regulatory T cells (Tregs) in solid organ transplantation is a promising approach for the prevention of graft rejection and induction of immunologic tolerance. Previous clinical studies have demonstrated the safety of Tregs in renal transplant recipients. Antigen-specific Tregs, such as chimeric antigen receptor (CAR)-Tregs, are expected to be more efficacious than polyclonal Tregs in homing to the target antigen. We have developed an autologous cell therapy (TX200-TR101) where a human leukocyte antigen (HLA) class I molecule A^∗02 (HLA-A^∗02)-CAR is introduced into autologous naive Tregs from a patient with HLA-A^∗02-negative end-stage renal disease (ESRD) awaiting an HLA-A^∗02-positive donor kidney.

Methods

This article describes the design of the STEADFAST study, a first-in-human, phase I/IIa, multicenter, open-label, single-ascending dose, dose-ranging study to assess TX200-TR101 in living-donor renal transplant recipients. Up to 15 transplant recipients will receive TX200-TR101 and will be followed up for a total of 84 weeks post-transplant, alongside a control cohort of up to 6 transplant recipients. All transplant recipients will receive a standard of care immunosuppressive regimen, with the intent of intensified tapering of the regimen in the TX200-TR101 cohort.

Results

The primary end point is the incidence and severity of treatment-emergent adverse events (AEs) within 28 days post–TX200-TR101 infusion. Other end points include additional safety parameters, clinical and renal outcome parameters, and the evaluation of biomarkers.

Conclusion

The STEADFAST study represents the next frontier in adoptive cell therapies. TX200-TR101 holds great potential to prevent immune-mediated graft rejection and induce immunologic tolerance after HLA-A^∗02-mismatched renal transplantation.

Immune-Related Genes for Predicting Future Kidney Graft Loss: A Study Based on GEO Database

Objective

We aimed to identify feature immune-related genes that correlated with graft rejection and to develop a prognostic model based on immune-related genes in kidney transplantation.

Methods

Gene expression profiles were obtained from the GEO database. The GSE36059 dataset was used as a discovery cohort. Then, differential expression analysis and a machine learning method were performed to select feature immune-related genes. After that, univariate and multivariate Cox regression analyses were used to identify prognosis-related genes. A novel Riskscore model was built based on the results of multivariate regression. The levels of these feature genes were also confirmed in an independent single-cell dataset and other GEO datasets.

Results

15 immune-related genes were expressed differently between non-rejection and rejection kidney allografts. Those differentially expressed immune-related genes (DE-IRGs) were mainly associated with immune-related biological processes and pathways. Subsequently, a 5-immune-gene signature was constructed and showed favorable predictive results in the GSE21374 dataset. Recipients were divided into the high-risk and low-risk groups according to the median value of RiskScore. The GO and KEGG analysis indicated that the differentially expressed genes (DEGs) between high-risk and low-risk groups were mainly involved in inflammatory pathways, chemokine-related pathways, and rejection-related pathways. Immune infiltration analysis demonstrated that RiskScore was potentially related to immune infiltration. Kaplan-Meier survival analysis suggested that recipients in the high-risk group had poor graft survival. AUC values of 1- and 3-year graft survival were 0.804 and 0.793, respectively.

Conclusion

Our data suggest that this immune-related prognostic model had good sensitivity and specificity in predicting the 1- and 3-year kidney graft survival and might act as a useful tool for predicting kidney graft loss.

Taurodeoxycholic acid and valine reverse obesity-associated augmented alloimmune responses and prolong allograft survival

Obesity initiates a chronic inflammatory network linked to perioperative complications and increased acute rejection rates in organ transplantation. Bariatric surgery is the most effective treatment of obesity recommended for morbidly obese transplant recipients. Here, we delineated the effects of obesity and bariatric surgery on alloimmunity and transplant outcomes in diet-induced obese (DIO) mice. Allograft survival was significantly shorter in DIO-mice. When performing sleeve gastrectomies (SGx) prior to transplantation, we found attenuated T cell-derived alloimmune responses resulting in prolonged allograft survival. Administering taurodeoxycholic acid (TDCA) and valine, metabolites depleted in DIO-mice and restored through SGx, prolonged graft survival in DIO-mice comparable with SGx an dampened Th1 and Th17 alloimmune responses while Treg frequencies and CD4+ T cell-derived IL-10 production were augmented. Moreover, in recipient animals treated with TDCA/valine, levels of donor-specific antibodies had been reduced. Mechanistically, TDCA/valine restrained inflammatory M1-macrophage polarization through TGR5 that compromised cAMP signaling and inhibited macrophage-derived T cell activation. Consistently, administering a TGR5 agonist to DIO-mice prolonged allograft survival. Overall, we provide novel insights into obesity-induced inflammation and its impact on alloimmunity. Furthermore, we introduce TDCA/valine as a noninvasive alternative treatment for obese transplant patients.

Targeting Interleukin-10 Restores Graft Microvascular Supply and Airway Epithelium in Rejecting Allografts

Interleukin-10 (IL-10) is a vital regulatory cytokine, which plays a constructive role in maintaining immune tolerance during an alloimmune inflammation. Our previous study highlighted that IL-10 mediated immunosuppression established the immune tolerance phase and thereby modulated both microvascular and epithelial integrity, which affected inflammation-associated graft malfunctioning and sub-epithelial fibrosis in rejecting allografts. Here, we further investigated the reparative effects of IL-10 on microvasculature and epithelium in a mouse model of airway transplantation. To investigate the IL-10 mediated microvascular and epithelial repair, we depleted and reconstituted IL-10, and monitored graft microvasculature, airway epithelium, and associated repair proteins. Our data demonstrated that both untreated control allografts and IL-10 (−) allografts showed a significant early (d6) increase in microvascular leakiness, drop-in tissue oxygenation, blood perfusion, and denuded airway epithelium, which is associated with loss of adhesion protein Fascin-1 and β-catenin on vascular endothelial cells at d10 post-transplantation. However, IL-10 (+) promotes early microvascular and airway epithelial repair, and a proportional increase in endothelial Fascin-1, and β-catenin at d10 post-transplantation. Moreover, airway epithelial cells also express a significantly higher expression of FOXJ1 and β-catenin in syngrafts and IL-10 (+) allografts as compared to IL-10 (−) and untreated controls at d10 post-transplantation. Collectively, these findings demonstrated that IL-10 mediated microvascular and epithelial changes are associated with the expression of FOXJ1, β-catenin, and Fascin-1 proteins on the airway epithelial and vascular endothelial cells, respectively. These findings establish a potential reparative modulation of IL-10 associated microvascular and epithelial repair, which could provide a vital therapeutic strategy to facilitate graft repair in clinical settings.

Combination Biomarker of Immune Checkpoints Predict Prognosis of Urothelial Carcinoma

In contrast to Western counties, the incidence of urothelial carcinoma (UC) remains mar-edly elevated in Taiwan. Regulatory T cells (Tregs) play a crucial role in limiting immune responses within the tumor microenvironment. To elucidate the relationship between immune checkpoints in the tumor immune microenvironment and UC progression, we utilize the Gene Expression Omnibus (GEO) to analyze a microarray obtained from 308 patients with UC. We observed that the expression level of CD276 or TIM-3 was positively correlated with late-stage UC and poor prognosis. Patients with simultaneously high CD276 and TIM-3 expression in tumors have significantly reduced both univariate and multivariate survival, indicating that mRNA levels of these immune checkpoints could be independent prognostic biomarkers for UC overall survival and recurrence. Our cohort study showed rare CD8+ cytotoxic T-cells and Tregs infiltration during early-stage UC-known as cold tumors. Approximately 30% of late-stage tumors exhibited highly infiltrated cytotoxic T cells with high PD-1 and FOXP3 expression, which implied that cytotoxic T cells were inhibited in the advanced UC microenvironment. Collectively, our findings provide a better prognosis prediction by combined immune checkpoint biomarkers and a basis for early-stage UC standard treatment to convert cold tumors into hot tumors, followed by immune checkpoint therapy.

Correlation between aryl hydrocarbon receptor and IL-17+ and Foxp3+ T-cell infiltration in bladder cancer

Bladder cancer (BC) is one of the most prevalent cancers around the world and, if not treated well, has high morbidity and mortality. Many studies have indicated that there may be various roles for the aryl hydrocarbon receptor (AHR) in the immune system. The aim of this study was to determine the frequency of Foxp3⁺ regulatory T (Treg) and T helper 17 cells (Th17) in BC tissue in comparison with controls and determine the relationship between AHR, Foxp3⁺ Treg and Th17 cells in BC. A total of 40 patients with BC were enrolled in this study. The control group was selected from non-tumoural parts of bladder tissues from the patients who have undergone cystoscopy. The percentage of regulatory T cells (Foxp3⁺ /CD4⁺ ) and Th17 (IL-17⁺ /CD4⁺ ), as well as AHR⁺ cells in BC tissues and controls, were determined by immunohistochemistry. The results of this study showed that the number of Foxp3⁺ Treg and Th17 is significantly higher in bladder tumour tissues in comparison with non-tumoural tissues. Also, the percentage of AHR⁺ lymphocytes and AHR⁺ cells was increased significantly in bladder tumour tissues rather than non-tumoural tissues. This study also found a relation between AHR and Foxp3⁺ /CD4⁺ T lymphocytes ratio cells in BC. The percentage of Foxp3⁺ Tregs and AHR⁺ cells were significantly correlated with the grade and stage of BC. An increase in the percentage of Foxp3⁺ Treg and Th17 cells may play an important role in tumour immunity; and determining the relationship between AHR and differentiation of Th17/Foxp3⁺ Treg in BC can lead to a potential cancer therapeutic possibility.

Clinical liver transplant tolerance: Recent topics

BACKGROUND

Immunosuppression is essential after organ transplantation to prevent severe graft injury due to rejection, but in long-term, transplanted organs are generally accepted with minimal dose of immunosuppression, and adverse effects of it such as renal dysfunction, diabetes and development of malignancies might become to exceed over the benefits in majority of the cases. Accordingly, to achieve the immunologic tolerance has been the ultimate goal in organ transplantation, and the liver has been well recognized as the tolerogenic organ compared to other organs.

METHODS

We referred the reported studies showing the actual protocol to achieve the immunologic tolerance after clinical liver transplantation.

RESULTS

Actually, two main procedures as "elective weaning of immunosuppression" and/or "cell therapy" using various immune-related cells have been introduced to induce the immunologic tolerance in clinical liver transplantation. The cell therapy, especially using regulatory T-cell has been reported to achieve definitive immunologic tolerance in living donor liver transplantation.

CONCLUSION

Although it is still developing, the induction of immunologic tolerance in clinical liver transplantation is realistic. Herein, the current topics of immunologic tolerance in liver transplantation is described.

Regulatory T Cell Therapy of Graft-versus-Host Disease: Advances and Challenges

Graft-versus-host disease (GVHD) is the leading cause of morbidity and mortality after allogeneic hematopoietic stem cell transplantation (allo-HSCT). Immunomodulation using regulatory T cells (Tregs) offers an exciting option to prevent and/or treat GVHD as these cells naturally function to maintain immune homeostasis, can induce tolerance following HSCT, and have a tissue reparative function. Studies to date have established a clinical safety profile for polyclonal Tregs. Functional enhancement through genetic engineering offers the possibility of improved potency, specificity, and persistence. In this review, we provide the most up to date preclinical and clinical data on Treg cell therapy with a particular focus on GVHD. We discuss the different Treg subtypes and highlight the pharmacological and genetic approaches under investigation to enhance the application of Tregs in allo-HSCT. Lastly, we discuss the remaining challenges for optimal clinical translation and provide insights as to future directions of the field.

MicroRNA-223 modulates the IL-4-medicated macrophage M2-type polarization to control the progress of sepsis

MicroRNAs play a variety of roles in the progress of inflammation. Herein, we investigated the roles of miR-223 in governing macrophage polarization balance in the progress of sepsis. We firstly observed that miR-223 was down-regulated at the early phase and up-regulated at the late phase of sepsis in macrophages; the levels of miR-223 were positively correlated to the ratio of M2 macrophages during sepsis. In miR-223 knockout mice, we observed that miR-223 was dispensable for efficient pro-inflammatory responses, but was required for efficient M2-associated phenotype and function. miR-223 deletion increased clinical scores of sepsis, leading to increased mortality in septic mice. Furthermore, we found that miR-223 expression in M2-type macrophages was controlled by interleukin (IL)-4, but not IL-10; IL-4 antibodies were able to downregulate the levels of miR-223, increased the expression of targeted genes Nfat5 and Rasa1, reduced the ratio of M2 macrophages, resulting in a decreased survival rate in septic mice. Meanwhile, miR-223 deficient macrophages appeared a markedly decreased M2-type polarization when induced by IL-4, but did not affect macrophages skew to M2 phenotype induced by IL-10. Taken together, our results demonstrate that miR-223 acts as an important regulator to modulate IL-4-meditated M2-type polarization of macrophages via targeting to Nfat5 and Rasa1 to control the progress of sepsis.

Therapeutic Potential of HLA-I Polyreactive mAbs Mimicking the HLA-I Polyreactivity and Immunoregulatory Functions of IVIg

HLA class-I (HLA-I) polyreactive monoclonal antibodies (mAbs) reacting to all HLA-I alleles were developed by immunizing mice with HLA-E monomeric, α-heavy chain (αHC) open conformers (OCs). Two mAbs (TFL-006 and TFL-007) were bound to the αHC's coated on a solid matrix. The binding was inhibited by the peptide 117AYDGKDY123, present in all alleles of the six HLA-I isoforms but masked by β2-microglobulin (β2-m) in intact HLA-I trimers (closed conformers, CCs). IVIg preparations administered to lower anti-HLA Abs in pre-and post-transplant patients have also shown HLA-I polyreactivity. We hypothesized that the mAbs that mimic IVIg HLA-I polyreactivity might also possess the immunomodulatory capabilities of IVIg. We tested the relative binding affinities of the mAbs and IVIg for both OCs and CCs and compared their effects on (a) the phytohemagglutinin (PHA)-activation T-cells; (b) the production of anti-HLA-II antibody (Ab) by B-memory cells and anti-HLA-I Ab by immortalized B-cells; and (c) the upregulation of CD4+, CD25+, and Fox P3+ T-regs. The mAbs bound only to OC, whereas IVIg bound to both CC and OC. The mAbs suppressed blastogenesis and proliferation of PHA-activated T-cells and anti-HLA Ab production by B-cells and expanded T-regs better than IVIg. We conclude that a humanized version of the TFL-mAbs could be an ideal, therapeutic IVIg-mimetic.

Regulatory T Cells in GVHD Therapy

Graft versus host disease (GVHD) is a common complication and the leading cause of morbidity and mortality after allogeneic hematopoietic stem cell transplantation (allo-HSCT). Pharmacological immunosuppression used in GVHD prophylaxis and treatment lacks specificity and can increase the likelihood of infection and relapse. Regulatory T lymphocytes (Tregs) play a vital role in restraining excessive immune responses and inducing peripheral immune tolerance. In particular, clinical trials have demonstrated that Tregs can prevent and treat GVHD, without increasing the risk of relapse and infection. Hence, adoptive transfer of Tregs to control GVHD using their immunosuppressive properties represents a promising therapeutic approach. To optimally apply Tregs for control of GVHD, a thorough understanding of their biology is necessary. In this review, we describe the biological characteristics of Tregs, including how the stability of FOXP3 expression can be maintained. We will also discuss the mechanisms underlying Tregs-mediated modulation of GVHD and approaches to effectively increase Tregs’ numbers. Finally, we will examine the developing trends in the use of Tregs for clinical therapy.

Unraveling the Crucial Roles of FoxP3+ Regulatory T Cells in Vascularized Composite Allograft Tolerance Induction and Maintenance

BACKGROUND

The role of regulatory T cells (Treg) in tolerance induction of vascularized composite allotransplantation (VCA) remains unclear. This study was designed to examine characteristics of Treg after VCA and their capacity to rescue allografts from rejection.

METHODS

Osteomyocutaneous allografts were transplanted from Balb/c to C57BL/6 mice. All mice received costimulatory blockade and a short course of rapamycin. To elucidate the role of Treg for tolerance induction, Treg depletion was performed at postoperative day (POD) 0, 30, or 90. To assess capacity of Treg to rescue allografts from rejection, an injection of 2 × 106 Treg isolated from tolerant mice was applied.

RESULTS

Eighty percent of VCA recipient mice using costimulatory blockade and rapamycin regimen developed tolerance. The tolerant recipients had a higher ratio of circulating Treg to effector T cells and elevated interleukin-10 at POD 30. A significantly higher rejection rate was observed when Treg were depleted at POD 30. But Treg depletion at POD 90 had no effect on tolerance. Treg from tolerant recipients showed stronger suppressive potential and the ability to rescue allografts from rejection. Furthermore, transplanted Treg-containing skin grafts from tolerant mice delayed rejection elicited by adoptively transferred effector T cells to Rag2-/- mice.

CONCLUSIONS

Circulating Treg are crucial for inducing VCA tolerance in the early posttransplant phase, and allograft-residing Treg may maintain tolerance. Treg may, therefore, serve as a potential cellular therapeutic to improve VCA outcomes.

IL-10 Mediated Immunomodulation Limits Subepithelial Fibrosis and Repairs Airway Epithelium in Rejecting Airway Allografts

Interleukin-10 plays a vital role in maintaining peripheral immunotolerance and favors a regulatory immune milieu through the suppression of T effector cells. Inflammation-induced microvascular loss has been associated with airway epithelial injury, which is a key pathological source of graft malfunctioning and subepithelial fibrosis in rejecting allografts. The regulatory immune phase maneuvers alloimmune inflammation through various regulatory modulators, and thereby promotes graft microvascular repair and suppresses the progression of fibrosis after transplantation. The present study was designed to investigate the therapeutic impact of IL-10 on immunotolerance, in particular, the reparative microenvironment, which negates airway epithelial injury, and fibrosis in a mouse model of airway graft rejection. Here, we depleted and reconstituted IL-10, and serially monitored the phase of immunotolerance, graft microvasculature, inflammatory cytokines, airway epithelium, and subepithelial collagen in rejecting airway transplants. We demonstrated that the IL-10 depletion suppresses FOXP3+ Tregs, tumor necrosis factor-inducible gene 6 protein (TSG-6), graft microvasculature, and establishes a pro-inflammatory phase, which augments airway epithelial injury and subepithelial collagen deposition while the IL-10 reconstitution facilitates FOXP3+ Tregs, TSG-6 deposition, graft microvasculature, and thereby favors airway epithelial repair and subepithelial collagen suppression. These findings establish a potential reparative modulation of IL-10-associated immunotolerance on microvascular, epithelial, and fibrotic remodeling, which could provide a vital therapeutic option to rescue rejecting transplants in clinical settings.

T cell receptor repertoires within liver allografts are different to those in the peripheral blood

BACKGROUND & AIMS

T cells are the main mediators of allogeneic immune responses. Specific T cell clones can be tracked by their unique T cell receptor (TCR), but specificity and function remain elusive and have not been investigated in human liver biopsies thus far.

METHODS

TCR repertoire analysis of CD4⁺, CD8⁺, and regulatory T cells of the peripheral blood and liver graft was performed in 7 liver transplant recipients with either stable course (non-rejector, NR), subclinical cellular rejection (SCR), or acute cellular rejection (ACR) during an observation period from pre-transplant to 6 years post-transplant. Furthermore, donor-reactive T cells, identified by their expression of CD154 and glycoprotein A repetitions predominant (GARP) after allogeneic activation, were tracked longitudinally in peripheral blood and within the liver allograft.

RESULTS

Although overall clonality of the TCR repertoire did not increase in peripheral blood after liver transplantation, clonality of donor-reactive CD4⁺ and regulatory T cells increased and these clones accumulated within the liver graft. Surprisingly, the TCR repertoires between the liver graft and the periphery were distinct and showed only limited overlap. Notably, during ACR, TCR repertoires aligned suggesting either graft-specific homing or release of activated T cells from the graft.

CONCLUSIONS

This is the first study comparing TCR repertoires between liver grafts and blood in patients with NR, SCR, and ACR. Moreover, we attribute specificity and function to a subgroup of intragraft T cell populations. Given the limited overlap between peripheral blood and intragraft repertoires, future studies investigating function and specificities of T cells after liver transplantation should focus on the intragraft immune response.

LAY SUMMARY

In solid organ transplantation, T cells are key mediators of the recipient's immune response directed at the transplanted organ. In our study, we characterised the T cell repertoire in a cohort of 7 liver transplant recipients. We demonstrate that donor-specific T cells expand clonally and accumulate in the transplanted liver. Moreover, we show that the composition of T cells in peripheral blood differs from the T cells in the liver allograft, only aligning in the context of acute cellular rejection but not in normal graft or subclinical cellular rejection. This indicates that the intragraft immune response is not mirrored in the peripheral blood. Our findings clarify the importance of protocol liver biopsies in identifying intragraft immune responses for future investigations of allo-directed immune responses.

The positive effect of pregnancy in rheumatoid arthritis and the use of medications for the management of rheumatoid arthritis during pregnancy

Rheumatoid arthritis (RA) is an autoimmune systemic inflammatory disorder that is mostly characterised by progressive symmetrical joint destruction, particularly in the wrist and fingers, while it may also affect additional joints and several organs, such as the skin, heart, blood vessels, and lungs. It is identified by raised anti-rheumatoid factor and anti-cyclic citrullinated peptide antibodies. The chemical mediators involved in the activity of RA are IL-1β, TNF-α, and IL-6. Pregnancy exerts a positive effect on RA that helps to modulate the disease condition. Different hypotheses are recommended to explain the ameliorating effect of pregnancy in RA. RA cannot be completely cured. The treatment goal is the attrition of pain and inflammation and the further progression of the disease. Long-term management of RA is carried out using disease-modifying antirheumatic drugs (DMARDs). Therapy of acute flares can be done with Non-steroidal anti-inflammatory drugs (NSAIDs) accompanied by ad interim usage of glucocorticoids. Biologic response modifiers are also available; they act by abolishing the activity of T- cells. However, it is necessary to select the correct treatment regimen when it comes to the management of RA in pregnancy.

Regulatory T cells in autoimmune hepatitis: an updated overview

Regulatory T-cells (Tregs) are key players in the maintenance of immune homeostasis by preventing immune responses to self-antigens. Defects in Treg frequency and/or function result in overwhelming CD4 and CD8 T cell immune responses participating in the autoimmune attack. Perpetuation of autoimmune damage is also favored by Treg predisposition to acquire effector cell features upon exposure to a proinflammatory challenge. Treg impairment plays a permissive role in the initiation and perpetuation of autoimmune liver diseases, namely autoimmune hepatitis, primary biliary cholangitis and primary sclerosing cholangitis. In this Review, we outline studies reporting the role of Treg impairment in the pathogenesis of these conditions and discuss methods to restore Treg number and function either by generation/expansion in the test tube or through in vivo expansion upon administration of low dose IL-2. Challenges and caveats of these potential therapeutic strategies are also reviewed and discussed.

Immunological Risk Factors in Recurrent Pregnancy Loss: Guidelines Versus Current State of the Art

Around 1-5% of all couples experience recurrent pregnancy loss (RPL). Established risk factors include anatomical, genetic, endocrine, and hemostatic alterations. With around 50% of idiopathic cases, immunological risk factors are getting into the scientific focus, however international guidelines hardly take them into account. Within this review, the current state of immunological risk factors in RPL in international guidelines of the European Society of Reproduction and Embryology (ESHRE), American Society of Reproductive Medicine (ASRM), German/Austrian/Swiss Society of Obstetrics and Gynecology (DGGG/OEGGG/SGGG) and the Royal College of Obstetricians and Gynecologists (RCOG) are evaluated. Special attention was drawn to recommendations in the guidelines regarding diagnostic factors such as autoantibodies, natural killer cells, regulatory T cells, dendritic cells, plasma cells, and human leukocyte antigen system (HLA)-sharing as well as treatment options such as corticosteroids, intralipids, intravenous immunoglobulins, aspirin and heparin in RPL. Finally, the current state of the art focusing on both diagnostic and therapeutic options was summarized.

Regulatory T Cells for the Induction of Transplantation Tolerance

Organ transplantation is the optimal treatment for terminal and irreversible organ failure. Achieving transplantation tolerance has long been the ultimate goal in the field of transplantation. Regulatory T cell (Treg)-based therapy is a promising novel approach for inducing donor organ-specific tolerance. Tregs play critical roles in the maintenance of immune homeostasis and self-tolerance, by promoting transplantation tolerance through a variety of mechanisms on different target cells, including anti-inflammatory cytokine production, induction of apoptosis, disruption of metabolic pathways, and mutual interaction with dendritic cells. The continued success of Treg-based therapy in the clinical setting is critically dependent on preclinical studies that support its translational potential. However, although some initial clinical trials of adoptive Treg therapy have successively demonstrated safety and efficacy for immunosuppressant minimization and transplantation tolerance induction, most Treg-based hematopoietic stem cell and solid organ clinical trials are still in their infancy. These clinical trials have not only focused on safety and efficacy but also included optimization and standardization protocols of good manufacturing practice regarding cell isolation, expansion, dosing, timing, specificity, quality control, concomitant immunosuppressants, and post-administration monitoring. We herein report a brief introduction of Tregs, including their phenotypic and functional characterization, and focus on the clinical translation of Treg-based therapeutic applications in the setting of transplantation.

Regulatory T Cell Therapy Following Liver Transplantation

Liver transplantation (LT) is considered the gold standard of curative treatment for patients with end-stage liver disease or nonresectable hepatic malignant tumors. Rejection after LT is the main nontechnical factor affecting the prognosis of recipients. Medical and surgical advances, combined with improved immunosuppression with drugs such as calcineurin inhibitors (CNIs), have contributed to an increase in 1-year graft survival to around 80%. However, medium- and long-term improvements in LT outcomes have lagged behind. Importantly, CNIs and other classical immunosuppressive drugs are associated with significant adverse effects, including malignancies, cardiovascular disease, and severe renal dysfunction. Immunomodulation using regulatory T cells (Tregs) is emerging as a promising alternative to classical immunosuppression. Since their discovery, the immunomodulatory effects of Tregs have been demonstrated in a range of diseases. This has rejuvenated the interest in using Tregs as a therapeutic strategy to induce immune tolerance after LT. In this review, we first summarize the discovery and development of Tregs. We then review the preclinical data supporting their production, mechanism of action, and therapeutic efficacy followed by a summary of relevant clinical trials. Finally, we discuss the outstanding challenges of Treg therapy and its future prospects for routine use in LT.

Analysis of chicken macrophage functions and gene expressions following infectious bronchitis virus M41 infection

Infectious bronchitis virus (IBV) is a pathogenic coronavirus with high morbidity and mortality in chicken breeding. Macrophages with normal biofunctions are essential for host immune responses. In this study, the HD11 chicken macrophage cell line and chicken peripheral blood mononuclear cell-derived macrophages (PBMCs-Mφ) were infected with IBV at multiplicity of infection (MOI) of 10. The dynamic changes of their biofunctions, including cell viability, pathogen elimination function, phagocytic ability, and gene expressions of related proteins/mediators in innate and acquired immunity, inflammation, autophagy and apoptosis were analyzed. Results showed that IBV infection decreased chicken macrophage viability and phagocytic ability, and increased pathogen elimination function. Moreover, IBV augmented the gene expressions of most related proteins in macrophages involved in multiple host bioprocesses, and the dynamic changes of gene expressions had a close relationship with virus replication. Among them, MHCII, Fc receptor, TLR3, IFN-α, CCL4, MIF, IL-1β, IL-6, and iNOS showed significantly higher expressions in IBV-infected cells. However, TLR7, MyD88, MDA5, IFN-γ, MHCII, Fc receptor, MARCO, CD36, MIF, XCL1, CXCL12, TNF-α, iNOS, and IL-10 showed early decreased expressions. Overall, chicken macrophages play an important role in host innate and acquired immune responses to resist IBV infection, despite early damage or suppression. Moreover, the IBV-induced autophagy and apoptosis might participate in the virus-host cell interaction which is attributed to the biological process.

Regulatory T cells mediated immunomodulation during asthma: a therapeutic standpoint

Asthma is an inflammatory disease of the lung airway network, which is initiated and perpetuated by allergen-specific CD4⁺ T cells, IgE antibodies, and a massive release of Th2 cytokines. The most common clinical manifestations of asthma progression include airway inflammation, pathological airway tissue and microvascular remodeling, which leads to airway hyperresponsiveness (AHR), and reversible airway obstruction. In addition to inflammatory cells, a tiny population of Regulatory T cells (Tregs) control immune homeostasis, suppress allergic responses, and participate in the resolution of inflammation-associated tissue injuries. Preclinical and clinical studies have demonstrated a tremendous therapeutic potential of Tregs in allergic airway disease, which plays a crucial role in immunosuppression, and rejuvenation of inflamed airways. These findings supported to harness the immunotherapeutic potential of Tregs to suppress airway inflammation and airway microvascular reestablishment during the progression of the asthma disease. This review addresses the therapeutic impact of Tregs and how Treg mediated immunomodulation plays a vital role in subduing the development of airway inflammation, and associated airway remodeling during the onset of disease.

IL-10 producing type 2 innate lymphoid cells prolong islet allograft survival

Type 2 innate lymphoid cells (ILC2s) are a subset of ILCs with critical roles in immunoregulation. However, the possible role of ILC2s as immunotherapy against allograft rejection remains unclear. Here, we show that IL‐33 significantly prolonged islet allograft survival. IL‐33‐treated mice had elevated numbers of ILC2s and regulatory T cells (Tregs). Depletion of Tregs partially abolished the protective effect of IL‐33 on allograft survival, and additional ILC2 depletion in Treg‐depleted DEREG mice completely abolished the protective effects of IL‐33, indicating that ILC2s play critical roles in IL‐33‐mediated islet graft protection. Two subsets of ILC2s were identified in islet allografts of IL‐33‐treated mice: IL‐10 producing ILC2s (ILC2¹⁰) and non‐IL‐10 producing ILC2s (non‐ILC¹⁰). Intravenous transfer of ILC2¹⁰ cells, but not non‐ILC¹⁰, prolonged islet allograft survival in an IL‐10‐dependent manner. Locally transferred ILC2¹⁰ cells led to long‐term islet graft survival, suggesting that ILC2¹⁰ cells are required within the allograft for maximal suppressive effect and graft protection. This study has uncovered a major protective role of ILC2¹⁰ in islet transplantation which could be potentiated as a therapeutic strategy.

Dominant regulation of long-term allograft survival is mediated by microRNA-142

Organ transplantation is often lifesaving, but the long-term deleterious effects of combinatorial immunosuppression regimens and allograft failure cause significant morbidity and mortality. Long-term graft survival in the absence of continuing immunosuppression, defined as operational tolerance, has never been described in the context of multiple major histocompatibility complex (MHC) mismatches. Here, we show that miR-142 deficiency leads to indefinite allograft survival in a fully MHC mismatched murine cardiac transplant model in the absence of exogenous immunosuppression. We demonstrate that the cause of indefinite allograft survival in the absence of miR-142 maps specifically to the T cell compartment. Of therapeutic relevance, temporal deletion of miR-142 in adult mice prior to transplantation of a fully MHC mismatched skin allograft resulted in prolonged allograft survival. Mechanistically, miR-142 directly targets Tgfbr1 for repression in regulatory T cells (TREG ). This leads to increased TREG sensitivity to transforming growth factor - beta and promotes transplant tolerance via an augmented peripheral TREG response in the absence of miR-142. These data identify manipulation of miR-142 as a promising approach for the induction of tolerance in human transplantation.

Gut Microbiota and Liver Interaction through Immune System Cross-Talk: A Comprehensive Review at the Time of the SARS-CoV-2 Pandemic

Background and aims: The gut microbiota is a complex ecosystem containing bacteria, viruses, fungi, yeasts and other single-celled organisms. It is involved in the development and maintenance of both innate and systemic immunity of the body. Emerging evidence has shown its role in liver diseases through the immune system cross-talk. We review herein literature data regarding the triangular interaction between gut microbiota, immune system and liver in health and disease. Methods: We conducted a search on the main medical databases for original articles, reviews, meta-analyses, randomized clinical trials and case series using the following keywords and acronyms and their associations: gut microbiota, microbiome, gut virome, immunity, gastrointestinal-associated lymphoid tissue (GALT), non-alcoholic fatty liver disease (NAFLD), non-alcoholic steato-hepatitis (NASH), alcoholic liver disease, liver cirrhosis, hepatocellular carcinoma. Results: The gut microbiota consists of microorganisms that educate our systemic immunity through GALT and non-GALT interactions. The latter maintain health but are also involved in the pathophysiology and in the outcome of several liver diseases, particularly those with metabolic, toxic or immune-mediated etiology. In this context, gut virome has an emerging role in liver diseases and needs to be further investigated, especially due to the link reported between severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) infection and hepatic dysfunctions. Conclusions: Changes in gut microbiota composition and alterations in the immune system response are involved in the pathogenesis of metabolic and immune-mediated liver diseases.

Cell Therapy in Solid Organ Transplantation

Transplantation is the only cure for end-stage organ failure. Current immunosuppressive drugs have two major limitations: 1) non antigen specificity, which increases the risk of cancer and infection diseases, and 2) chronic toxicity. Cell therapy appears to be an innovative and promising strategy to minimize the use of immunosuppression in transplantation and to improve long-term graft survival. Preclinical studies have shown efficacy and safety of using various suppressor cells, such as regulatory T cells, regulatory B cells and tolerogenic dendritic cells. Recent clinical trials using cellbased therapies in solid organ transplantation also hold out the promise of improving efficacy. In this review, we will briefly go over the rejection process, current immunosuppressive drugs, and the potential therapeutic use of regulatory cells in transplantation.

Pregnancy immune tolerance at the maternal-fetal interface

Pregnancy is a natural process that poses an immunological challenge because non-self fetus must be accepted. During the pregnancy period, the fetus as 'allograft' inherits maternal and also paternal antigens. For successful and term pregnancy, the fetus is tolerated and nurtured enjoying immune privileges that minimize the risk of being rejected by maternal immune system. Multiple mechanisms contribute to tolerate the semi-allogeneic fetus. Here, we summarize the recent progresses on how the maternal immune system actively collaborates to maintain the immune balance and maternal-fetal tolerance.

Time Course of Immune Response and Immunomodulation During Normal and Delayed Healing of Musculoskeletal Wounds

Single trauma injuries or isolated fractures are often manageable and generally heal without complications. In contrast, high-energy trauma results in multi/poly-trauma injury patterns presenting imbalanced pro- and anti- inflammatory responses often leading to immune dysfunction. These injuries often exhibit delayed healing, leading to fibrosis of injury sites and delayed healing of fractures depending on the intensity of the compounding traumas. Immune dysfunction is accompanied by a temporal shift in the innate and adaptive immune cells distribution, triggered by the overwhelming release of an arsenal of inflammatory mediators such as complements, cytokines and damage associated molecular patterns (DAMPs) from necrotic cells. Recent studies have implicated this dysregulated inflammation in the poor prognosis of polytraumatic injuries, however, interventions focusing on immunomodulating inflammatory cellular composition and activation, if administered incorrectly, can result in immune suppression and unintended outcomes. Immunomodulation therapy is promising but should be conducted with consideration for the spatial and temporal distribution of the immune cells during impaired healing. This review describes the current state of knowledge in the spatiotemporal distribution patterns of immune cells at various stages during musculoskeletal wound healing, with a focus on recent advances in the field of Osteoimmunology, a study of the interface between the immune and skeletal systems, in long bone fractures. The goals of this review are to (1) discuss wound and fracture healing processes of normal and delayed healing in skeletal muscles and long bones; (2) provide a balanced perspective on temporal distributions of immune cells and skeletal cells during healing; and (3) highlight recent therapeutic interventions used to improve fracture healing. This review is intended to promote an understanding of the importance of inflammation during normal and delayed wound and fracture healing. Knowledge gained will be instrumental in developing novel immunomodulatory approaches for impaired healing.

Immunomodulation Followed by Antigen-Specific Treg Infusion Controls Islet Autoimmunity

Optimal immune-based therapies for type 1 diabetes (T1D) should restore self-tolerance without inducing chronic immunosuppression. CD4⁺Foxp3⁺ regulatory T cells (T_regs) are a key cell population capable of facilitating durable immune tolerance. However, clinical trials with expanded T_regs in T1D and solid-organ transplant recipients are limited by poor T_reg engraftment without host manipulation. We showed that T_reg engraftment and therapeutic benefit in nonautoimmune models required ablative host conditioning. Here, we evaluated T_reg engraftment and therapeutic efficacy in the nonobese diabetic (NOD) mouse model of autoimmune diabetes using nonablative, combinatorial regimens involving the anti-CD3 (αCD3), cyclophosphamide (CyP), and IAC (IL-2/JES6-1) antibody complex. We demonstrate that αCD3 alone induced substantial T-cell depletion, impacting both conventional T cells (T_conv) and T_regs, subsequently followed by more rapid rebound of T_regs Despite robust depletion of host T_conv and host T_regs, donor T_regs failed to engraft even with interleukin-2 (IL-2) support. A single dose of CyP after αCD3 depleted rebounding host T_regs and resulted in a 43-fold increase in donor T_reg engraftment, yet polyclonal donor T_regs failed to reverse diabetes. However, infusion of autoantigen-specific T_regs after αCD3 alone resulted in robust T_reg engraftment within the islets and induced remission in all mice. This novel combinatorial therapy promotes engraftment of autoantigen-specific donor T_regs and controls islet autoimmunity without long-term immunosuppression.

Combined treatment with vitamin D3 and antibody agents suppresses secondary heart transplant rejection in the early postoperative period

BACKGROUND

Accelerated transplant rejection mediated by donor reactive memory T cells is another barrier to the induction of graft tolerance. The aim of this study was to investigate the immunosuppressing effects of vitamin D (1,25(OH)2D3), administered alone or in combination with a costimulatory blockade treatment, on rejection of secondary heart allografts in a mouse model.

METHODS

Circular full-thickness skin grafts from BALB/c mice were cut and grafted onto the lumbar regions of C57BL/6 mice as allo-primed recipients. Four weeks after skin grafting, the vascularized hearts from the BALB/c mice were transplanted heterotopically into the allo-primed recipients using a non-suture cuff technique. The recipients were then randomly divided into four groups and given either intraperitoneal injection of isotype, Ab, 1,25(OH)2D3, or a combination of Ab and 1,25(OH)2D3. Allograft incidence was determined by hematoxylin-eosin staining, and cytokine expression was assessed by the quantitative real-time polymerase chain reaction, enzyme-linked immunosorbent assays, and cytometric bead arrays. Spleen cells from the recipient were used to assess mixed lymphocyte reactions. Memory T cells and regulatory T cells (Tregs) in spleen cells were measured by flow cytometry.

RESULTS

The median allograft survival time was longer with the combined treatment with Ab and 1,25(OH)2D3 than with no treatment or with treatment with Ab or 1,25(OH)2D3 alone. The grafts were protected from infiltration by inflammatory cells and by inhibition of interleukin 2 and interferon gamma expression. Rejection was initially suppressed in the early postoperative period by a reduction in the number of memory T cells and induction of Foxp3⁺ Tregs, but this effect disappeared by day 15 after transplantation upon withdrawal of the treatment.

CONCLUSION

Vitamin D3 administered as an immunosuppressive agent, when combined with monoclonal antibody treatment, may protect heart grafts from memory T cell responses in a secondary heart transplant model.

Approaching treatment for immunological rejection of living-donor liver transplantation in rats

Background

The anti-immunological rejection therapy for small-for-size syndrome (SFSS) after live donor liver transplantation (LDLT) play a central role in keeping graft survival. The hepatocyte number and grafts function has undergone real-time changes with the proliferation and apoptosis of the grafts after reperfusion. Lacking an accurate and effective treatment regiments or indicators to guide the use of immunosuppressive drugs in SFS liver transplantation has made immunotherapy after SFS liver transplantation an urgent problem to be solved. Herein, we established small-for-size (SFS) and normal size liver transplantation model in rats to explore the effective indicators in guiding immunotherapy, to find an effective way for overcoming SFSS.

Methods

Lewis rats (donors) and BN rats (recipients) were used to mimic allograft liver transplantation and treated with tacrolimus. Local graft immune response was analyzed through haematoxylin and eosin and immunohistochemistry. Flow cytometry was used to assess the overall immune status of recipient. The pharmacokinetics mechanism of immunosuppressive drugs was explored through detecting CYP3A2 expression at mRNA level and protein levels.

Results

The results showed the local immune reaction of SFS grafts and systemic immune responses of recipient were significantly increased compared with those in normal size grafts and their recipient at four days after liver transplantation. Regression equation was used to regulate the tacrolimus dose which not only controlled tacrolimus serum concentration effectively but alleviated liver damage and improved survival rate.

Conclusions

This study showed that AST level and tacrolimus serum concentrations are effective indicators in guiding immunotherapy. Regression equation (T_D = − 0.494T_C-0.0035AST + 260.487) based on AST and tacrolimus serum concentration can be used as a reference for adjustment of immunotherapy after SFS liver transplantation, which is applicable in clinical practice.