Manipulating regulatory T cells: a promising strategy to treat autoimmunity

The immunopathogenesis of sarcoidosis

Sarcoidosis is a granulomatous multiorgan disease, thought to result from exposure to yet unidentified antigens in genetically susceptible individuals. The exaggerated inflammatory response that leads to granuloma formation is highly complex and involves the innate and adaptive immune system. Consecutive immunological studies using advanced technology have increased our understanding of aberrantly activated immune cells, mediators and pathways that influence the formation, maintenance and resolution of granulomas. Over the years, it has become increasingly clear that disease immunopathogenesis can only be understood if the clinical heterogeneity of sarcoidosis is taken into consideration, along with the distribution of immune cells in peripheral blood and involved organs. Most studies offer an immunological snapshot during disease course, while the cellular composition of both the circulation and tissue microenvironment may change over time. Despite these challenges, novel insights on the role of the immune system are continuously published, thus bringing the field forward. This review highlights current knowledge on the innate and adaptive immune responses involved in sarcoidosis pathogenesis, as well as the pathways involved in non-resolving disease and fibrosis development. Additionally, we describe proposed immunological mechanisms responsible for drug-induced sarcoid like reactions. Although many aspects of disease immunopathogenesis remain to be unraveled, the identification of crucial immune reactions in sarcoidosis may help identify new treatment targets. We therefore also discuss potential therapies and future strategies based on the latest immunological findings.

CPT-11 mitigates autoimmune diseases by suppressing effector T cells without affecting long-term anti-tumor immunity

The incidence of autoimmune diseases has significantly increased over the past 20 years. Excessive host immunoreactions and disordered immunoregulation are at the core of the pathogenesis of autoimmune diseases. The traditional anti-tumor chemotherapy drug CPT-11 is associated with leukopenia. Considering that CPT-11 induces leukopenia, we believe that it is a promising drug for the control of autoimmune diseases. Here, we show that CPT-11 suppresses T cell proliferation and pro-inflammatory cytokine production in healthy C57BL/6 mice and in complete Freund's adjuvant-challenged mice. We found that CPT-11 effectively inhibited T cell proliferation and Th1 and Th17 cell differentiation by inhibiting glycolysis in T cells. We also assessed CPT-11 efficacy in treating autoimmune diseases in models of experimental autoimmune encephalomyelitis and psoriasis. Finally, we proved that treatment of autoimmune diseases with CPT-11 did not suppress long-term immune surveillance for cancer. Taken together, these results show that CPT-11 is a promising immunosuppressive drug for autoimmune disease treatment.

Therapeutic Strategies for Immune Transformation in Parkinson’s Disease

Dysregulation of innate and adaptive immunity can lead to alpha-synuclein (α-syn) misfolding, aggregation, and post-translational modifications in Parkinson’s disease (PD). This process is driven by neuroinflammation and oxidative stress, which can contribute to the release of neurotoxic oligomers that facilitate dopaminergic neurodegeneration. Strategies that promote vaccines and antibodies target the clearance of misfolded, modified α-syn, while gene therapy approaches propose to deliver intracellular single chain nanobodies to mitigate α-syn misfolding, or to deliver neurotrophic factors that support neuronal viability in an otherwise neurotoxic environment. Additionally, transformative immune responses provide potential targets for PD therapeutics. Anti-inflammatory drugs represent one strategy that principally affects innate immunity. Considerable research efforts have focused on transforming the balance of pro-inflammatory effector T cells (Teffs) to favor regulatory T cell (Treg) activity, which aims to attenuate neuroinflammation and support reparative and neurotrophic homeostasis. This approach serves to control innate microglial neurotoxic activities and may facilitate clearance of α-syn aggregates accordingly. More recently, changes in the intestinal microbiome have been shown to alter the gut-immune-brain axis leading to suppressed leakage of bacterial products that can promote peripheral inflammation and α-syn misfolding. Together, each of the approaches serves to interdict chronic inflammation associated with disordered immunity and neurodegeneration. Herein, we examine research strategies aimed at improving clinical outcomes in PD.

Isolation of HLA-DR-naturally presented peptides identifies T-cell epitopes for rheumatoid arthritis

OBJECTIVE

Rheumatoid arthritis (RA) immunopathogenesis revolves around the presentation of poorly characterised self-peptides by human leucocyte antigen (HLA)-class II molecules on the surface of antigen-presenting cells to autoreactive CD4 +T cells. Here, we analysed the HLA-DR-associated peptidome of synovial tissue (ST) and of dendritic cells (DCs) pulsed with synovial fluid (SF) or ST, to identify potential T-cell epitopes for RA.

METHODS

HLA-DR/peptide complexes were isolated from RA ST samples (n=3) and monocyte-derived DCs, generated from healthy donors carrying RA-associated shared epitope positive HLA-DR molecules and pulsed with RA SF (n=7) or ST (n=2). Peptide sequencing was performed by high-resolution mass spectrometry. The immunostimulatory capacity of selected peptides was evaluated on peripheral blood mononuclear cells from patients with RA (n=29) and healthy subjects (n=12) by flow cytometry.

RESULTS

We identified between 103 and 888 HLA-DR-naturally presented peptides per sample. We selected 37 native and six citrullinated (cit)-peptides for stimulation assays. Six of these peptides increased the expression of CD40L on CD4 +T cells patients with RA, and specifically triggered IFN-γ expression on RA CD4 +T cells compared with healthy subjects. Finally, the frequency of IFN-γ-producing CD4 +T cells specific for a myeloperoxidase-derived peptide showed a positive correlation with disease activity.

CONCLUSIONS

We significantly expanded the peptide repertoire presented by HLA-DR molecules in a physiologically relevant context, identifying six new epitopes recognised by CD4 +T cells from patients with RA. This information is important for a better understanding of the disease immunopathology, as well as for designing tolerising antigen-specific immunotherapies.

Cell-based therapies for rheumatoid arthritis: opportunities and challenges

Rheumatoid arthritis (RA) is the most common immune-mediated inflammatory disease characterized by chronic synovitis that hardly resolves spontaneously. The current treatment of RA consists of nonsteroidal anti-inflammatory drugs (NSAIDs), glucocorticoids, conventional disease-modifying antirheumatic drugs (cDMARDs), biologic and targeted synthetic DMARDs. Although the treat-to-target strategy has been intensively applied in the past decade, clinical unmet needs still exist since a substantial proportion of patients are refractory or even develop severe adverse effects to current therapies. In recent years, with the deeper understanding of immunopathogenesis of the disease, cell-based therapies have exhibited effective and promising interventions to RA. Several cell-based therapies, such as mesenchymal stem cells (MSC), adoptive transfer of regulatory T cells (Treg), and chimeric antigen receptor (CAR)-T cell therapy as well as their beneficial effects have been documented and verified so far. In this review, we summarize the current evidence and discuss the prospect as well as challenges for these three types of cellular therapies in RA.

Role of Cytokines in Thymic Regulatory T Cell Generation: Overview and Updates

CD4⁺CD25⁺Foxp3⁺ Regulatory (Treg) T cells are mainly generated within the thymus. However, the mechanism of thymic Treg cell (tTreg cell) generation remains to be fully revealed. Although the functions of TCR/CD28 co-stimulation have been widely accepted, the functions of cytokines in the generation of tTreg cells remain highly controversial. In this review, we summarize the existing studies on cytokine regulation of tTreg cell generation. By integrating the key findings of cytokines in tTreg cell generation, we have concluded that four members of γc family cytokines (IL-2, IL-4, IL-7 and IL-15), transforming growth factor β (TGF-β), and three members of TNF superfamily cytokines (GITRL, OX40L and TNF-α) play vitally important roles in regulating tTreg cell generation. We also point out all disputed points and highlight critical scientific questions that need to be addressed in the future.

Mannose Treatment: A Promising Novel Strategy to Suppress Inflammation

High glucose and fructose intake have been proven to display pro-inflammatory roles during the progression of inflammatory diseases. However, mannose has been shown to be a special type of hexose that has immune regulatory functions. In this review, we trace the discovery process of the regulatory functions of mannose and summarize some past and recent studies showing the therapeutic functions of mannose in inflammatory diseases. We conclude that treatment with mannose can suppress inflammation by inducing regulatory T cells, suppressing effector T cells and inflammatory macrophages, and increasing anti-inflammatory gut microbiome. By summarizing all the important findings, we highlight that mannose treatment is a safe and promising novel strategy to suppress inflammatory diseases, including autoimmune disease and allergic disease.

The Liver and the Hepatic Immune Response in Trypanosoma cruzi Infection, a Historical and Updated View

Chagas disease was described more than a century ago and, despite great efforts to understand the underlying mechanisms that lead to cardiac and digestive manifestations in chronic patients, much remains to be clarified. The disease is found beyond Latin America, including Japan, the USA, France, Spain, and Australia, and is caused by the protozoan Trypanosoma cruzi. Dr. Carlos Chagas described Chagas disease in 1909 in Brazil, and hepatomegaly was among the clinical signs observed. Currently, hepatomegaly is cited in most papers published which either study acutely infected patients or experimental models, and we know that the parasite can infect multiple cell types in the liver, especially Kupffer cells and dendritic cells. Moreover, liver damage is more pronounced in cases of oral infection, which is mainly found in the Amazon region. However, the importance of liver involvement, including the hepatic immune response, in disease progression does not receive much attention. In this review, we present the very first paper published approaching the liver's participation in the infection, as well as subsequent papers published in the last century, up to and including our recently published results. We propose that, after infection, activated peripheral T lymphocytes reach the liver and induce a shift to a pro-inflammatory ambient environment. Thus, there is an immunological integration and cooperation between peripheral and hepatic immunity, contributing to disease control.

Induction of antigen-specific Treg cells in treating autoimmune uveitis via bystander suppressive pathways without compromising anti-tumor immunity

BACKGROUND

Induction of autoantigen-specific Treg cells that suppress tissue-specific autoimmunity without compromising beneficial immune responses is the holy-grail for immunotherapy to autoimmune diseases.

METHODS

In a model of experimental autoimmune uveitis (EAU) that mimics human uveitis, ocular inflammation was induced by immunization with retinal antigen interphotoreceptor retinoid-binding protein (IRBP). Mice were given intraperitoneal injection of αCD4 antibody (Ab) after the onset of disease, followed by administration of IRBP. EAU was evaluated clinically and functionally. Splenocytes, CD4⁺CD25^- and CD4⁺CD25⁺ T cells were sorted and cultured with IRBP or αCD3 Ab. T cell proliferation and cytokine production were assessed.

FINDINGS

The experimental approach resulted in remission of ocular inflammation and rescue of visual function in mice with established EAU. Mechanistically, the therapeutic effect was mediated by induction of antigen-specific Treg cells that inhibited IRBP-driven Th17 response in TGF-β and IL-10 dependent fashion. Importantly, the Ab-mediated immune tolerance could be achieved in EAU mice by administration of retinal autoantigens, arrestin but not limited to IRBP only, in an antigen-nonspecific bystander manner. Further, these EAU-suppressed tolerized mice did not compromise their anti-tumor T immunity in melanoma model.

INTERPRETATION

We successfully addressed a specific immunotherapy of EAU by in vivo induction of autoantigen-specific Treg cells without compromising host overall T cell immunity, which should have potential implication for patients with autoimmune uveitis.

FUNDING

This study was supported by the Natural Science Foundation of Guangdong Province and the Fundamental Research Fund of the State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center.

Exploring the role of immunotherapeutic drugs in autoimmune diseases: A comprehensive review

Autoimmune diseases are group of disorders where an immune response is mounted against the self. The prevalence and burden of this well established and recognised entity is on the rise. Irrespective of being a systemic or organ specific autoimmune disorder, the common underlying mechanism of action, is the imbalance in immune system resulting in loss of tolerance to self-antigens. The oral cavity is no alien to these disorders or to their influences. Pemphigus group of lesions, systemic lupus erythematosus, psoriasis and even Sjogren's syndrome are some of the established autoimmune disorders with prominent oral manifestations. Though these diseases are well documented and enumerated, however addressing them is where the dilemma lies. Science, research and discoveries are a crucial part of medical discipline which help in looking beyond the horizon. With the introduction of selective targeted immunotherapies for autoimmune diseases as a treatment modality either in solitary or in combination with the conventional immunosuppressive treatments, are emerging as a promising elixir for patients enduring them. However, being unique, exploration of these biologics from its inception, to its mechanism of action, recognition of its application and evaluation of its safety norms are equally vital. Therefore, this review aims to provide a comprehensive particular on the novel biologics, the immunotherapies in autoimmune disorders targeting the different cells, their receptors or cytokines of the immune system.

A deep dive into UV-based phototherapy: Mechanisms of action and emerging molecular targets in inflammation and cancer

UV-based phototherapy (including psoralen plus UVA (PUVA), UVB and UVA1) has a long, successful history in the management of numerous cutaneous disorders. Photoresponsive diseases are etiologically diverse, but most involve disturbances in local (and occasionally systemic) inflammatory cells and/or abnormalities in keratinocytes that trigger inflammation. UV-based phototherapy works by regulating the inflammatory component and inducing apoptosis of pathogenic cells. This results in a fascinating and complex network of simultaneous events-immediate transcriptional changes in keratinocytes, immune cells, and pigment cells; the emergence of apoptotic bodies; and the trafficking of antigen-presenting cells in skin-that quickly transform the microenvironment of UV-exposed skin. Molecular elements in this system of UV recognition and response include chromophores, metabolic byproducts, innate immune receptors, neurotransmitters and mediators such as chemokines and cytokines, antimicrobial peptides, and platelet activating factor (PAF) and PAF-like molecules that simultaneously shape the immunomodulatory effects of UV and their interplay with the microbiota of the skin and beyond. Phototherapy's key effects-proapoptotic, immunomodulatory, antipruritic, antifibrotic, propigmentary, and pro-prebiotic-promote clinical improvement in various skin diseases such as psoriasis, atopic dermatitis (AD), graft-versus-host disease (GvHD), vitiligo, scleroderma, and cutaneous T-cell lymphoma (CTCL) as well as prevention of polymorphic light eruption (PLE). As understanding of phototherapy improves, new therapies (UV- and non-UV-based) are being developed that will modify regulatory T-cells (Treg), interact with (resident) memory T-cells and /or utilize agonists and antagonists as well as antibodies targeting soluble molecules such as cytokines and chemokines, transcription factors, and a variety of membrane-associated receptors.

Regulatory T Cell Plasticity and Stability and Autoimmune Diseases

CD4⁺CD25⁺ regulatory T cells (Tregs) are a class of CD4⁺ T cells with immunosuppressive functions that play a critical role in maintaining immune homeostasis. However, in certain disease settings, Tregs demonstrate plastic differentiation, and the stability of these Tregs, which is characterized by the stable expression or protective epigenetic modifications of the transcription factor Foxp3, becomes abnormal. Plastic Tregs have some features of helper T (Th) cells, such as the secretion of Th-related cytokines and the expression of specific transcription factors in Th cells, but also still retain the expression of Foxp3, a feature of Tregs. Although such Th-like Tregs can secrete pro-inflammatory cytokines, they still possess a strong ability to inhibit specific Th cell responses. Therefore, the plastic differentiation of Tregs not only increases the complexity of the immune circumstances under pathological conditions, especially autoimmune diseases, but also shows an association with changes in the stability of Tregs. The plastic differentiation and stability change of Tregs play vital roles in the progression of diseases. This review focuses on the phenotypic characteristics, functions, and formation conditions of several plastic Tregs and also summarizes the changes of Treg stability and their effects on inhibitory function. Additionally, the effects of Treg plasticity and stability on disease prognosis for several autoimmune diseases were also investigated in order to better understand the relationship between Tregs and autoimmune diseases.

Regulatory T-cell expansion in oral and maxillofacial Langerhans cell histiocytosis

OBJECTIVE

Langerhans cell histiocytosis (LCH) is a rare myeloid-origin neoplasm characterized by the expansion and dissemination of CD1 a+/CD207+ dendritic cells (LCH cells), but the rarity of its occurrence has long impeded progress in understanding its pathology. We focus on the potentially important role that regulatory T cells (T-reg) play in the oral and maxillofacial LCH tumor microenvironment (TME).

STUDY DESIGN

Nine cases of oral and maxillofacial LCH, diagnosed from 2009 to 2019, were collected retrospectively from the affiliated hospitals of Southern Medical University. Immunohistochemistry was conducted characterizing T cells and T-reg phenotype. Data were evaluated by 1-sample Wilcoxon's test.

RESULTS

Significantly increased frequency and abnormal distributions of T-reg were identified in all the LCH lesion sections. Proliferating T-reg account for a mean average of 11.5% of the total T-cell subsets, with significant difference (Wilcoxon's test; P < .05).

CONCLUSIONS

T-reg expansion in the localized inflammatory TME leads to a failure of immune regulation by suppressing antitumor response, which can be a latent and significant factor contributing to LCH progression. However, T-reg may also acquire the capability for aiding in initiating T-cell responses under the "cytokine storm" at the beginning of LCH onset. T-reg might contribute to the augmentation of tissue repair by transforming growth factor-β (TGF-β), explaining the self-limiting character of LCH.

MCL-1 is essential for survival but dispensable for metabolic fitness of FOXP3+ regulatory T cells

FOXP3⁺ regulatory T (Treg) cells are essential for maintaining immunological tolerance. Given their importance in immune-related diseases, cancer and obesity, there is increasing interest in targeting the Treg cell compartment therapeutically. New pharmacological inhibitors that specifically target the prosurvival protein MCL-1 may provide this opportunity, as Treg cells are particularly reliant upon this protein. However, there are two distinct isoforms of MCL-1; one located at the outer mitochondrial membrane (OMM) that is required to antagonize apoptosis, and another at the inner mitochondrial membrane (IMM) that is reported to maintain IMM structure and metabolism via ATP production during oxidative phosphorylation. We set out to elucidate the relative importance of these distinct biological functions of MCL-1 in Treg cells to assess whether MCL-1 inhibition might impact upon the metabolism of cells able to resist apoptosis. Conditional deletion of Mcl1 in FOXP3⁺ Treg cells resulted in a lethal multiorgan autoimmunity due to the depletion of the Treg cell compartment. This striking phenotype was completely rescued by concomitant deletion of the apoptotic effector proteins BAK and BAX, indicating that apoptosis plays a pivotal role in the homeostasis of Treg cells. Notably, MCL-1-deficient Treg cells rescued from apoptosis displayed normal metabolic capacity. Moreover, pharmacological inhibition of MCL-1 in Treg cells resistant to apoptosis did not perturb their metabolic function. We conclude that Treg cells require MCL-1 only to antagonize apoptosis and not for metabolism. Therefore, MCL-1 inhibition could be used to manipulate Treg cell survival for clinical benefit without affecting the metabolic fitness of cells resisting apoptosis.

Adoptive Treg Cell Therapy in a Patient With Systemic Lupus Erythematosus

OBJECTIVE

Adoptive Treg cell therapy has great potential to treat autoimmune disease. Currently, very little is known about how these cells impact inflamed tissues. This study was undertaken to elucidate how autologous Treg cell therapy influences tissue inflammation in human autoimmune disease.

METHODS

We describe a systemic lupus erythematosus (SLE) patient with active skin disease who received adoptive Treg therapy. We comprehensively quantified Treg cells and immune activation in peripheral blood and skin, with data obtained at multiple time points posttreatment.

RESULTS

Deuterium tracking of infused Treg cells revealed the transient presence of cells in peripheral blood, accompanied by increased percentages of highly activated Treg cells in diseased skin. Flow cytometric analysis and whole transcriptome RNA sequencing revealed that Treg cell accumulation in skin was associated with a marked attenuation of the interferon-γ pathway and a reciprocal augmentation of the interleukin-17 (IL-17) pathway. This phenomenon was more pronounced in skin relative to peripheral blood. To validate these findings, we investigated Treg cell adoptive transfer of skin inflammation in a murine model and found that it also resulted in a pronounced skewing away from Th1 immunity and toward IL-17 production.

CONCLUSION

We report the first case of a patient with SLE treated with autologous adoptive Treg cell therapy. Taken together, our results suggest that this treatment leads to increased activated Treg cells in inflamed skin, with a dynamic shift from Th1 to Th17 responses.

A Novel Liposome Formulation Carrying Both an Insulin Peptide and a Ligand for Invariant Natural Killer T Cells Induces Accumulation of Regulatory T Cells to Islets in Nonobese Diabetic Mice

Type 1 diabetes (T1D) is an autoimmune disease caused by the destruction of pancreatic β cells by autoantigen-reactive diabetogenic cells. Antigen-specific therapies using islet autoantigens for restoring immune tolerance have emerged as promising approaches for the treatment of T1D but have been unsuccessful in humans. Herein, we report that RGI-3100-iB, a novel liposomal formulation carrying both α-galactosylceramide (α-GalCer), which is a representative ligand for invariant natural killer T (iNKT) cells, and insulin B chain 9-23 peptide, which is an epitope for CD4⁺ T cells, could induce the accumulation of regulatory T cells (Tregs) in islets in a peptide-dependent manner, followed by the remarkable prevention of diabetes onset in nonobese diabetic (NOD) mice. While multiple administrations of a monotherapy using either α-GalCer or insulin B peptide in a liposomal formulation was confirmed to delay/prevent T1D in NOD mice, RGI-3100-iB synergistically enhanced the prevention effect of each monotherapy and alleviated insulitis in NOD mice. Immunopathological analysis showed that Foxp3⁺ Tregs accumulated in the islets in RGI-3100-iB-treated mice. Cotransfer of diabetogenic T cells and splenocytes of NOD mice treated with RGI-3100-iB, but not liposomal α-GalCer encapsulating an unrelated peptide, to NOD-SCID mice resulted in the prevention of diabetes and elevation of Foxp3 mRNA expression in the islets. These data indicate that the migration of insulin B-peptide-specific Tregs to islet of NOD mice that are involved in the suppression of pathogenic T cells related to diabetes onset and progression could be enhanced by the administration of liposomes containing α-GalCer and insulin B peptide.

Preventing murine transfusion-related acute lung injury by expansion of CD4+ CD25+ FoxP3+ Tregs using IL-2/anti-IL-2 complexes

BACKGROUND

Transfusion-related acute lung injury (TRALI) is one of the most serious adverse events following transfusion, and there is no specific treatment in clinical practice. However, regulatory T cells (Tregs) have been suggested to play a potential role in the treatment of TRALI. This study investigated whether interleukin (IL)-2 or IL-2/anti-IL-2 complexes (IL-2c), which are mediators of Treg expansion, can modulate the severity of antibody-mediated TRALI in vivo.

STUDY DESIGN AND METHODS

This study utilized a mouse model of the "two-hit" mechanism: BALB/c mice were primed with lipopolysaccharide (LPS) as the first hit, and then TRALI was induced by injecting major histocompatibility complex Class I antibodies. Mice injected with LPS only or LPS combined with isotype control antibodies served as controls. For the Treg-depleted groups, mice were infused with anti-mouse IL-2Rα first and then subjected to the same treatments as the TRALI group. Regarding IL-2- and IL-2c-treated mice, recombinant murine IL-2 or IL-2c was intraperitoneally administered to mice for 5 consecutive days before induction of the TRALI model. Samples were collected 2 hours after TRALI induction.

RESULTS

Prophylactic administration of IL-2 or IL-2c to mice prevented the onset of edema, pulmonary protein levels, and proinflammatory factors that inhibited polymorphonuclear neutrophil aggregation in the lungs. Furthermore, the percentage of CD4⁺ CD25⁺ FoxP3⁺ Tregs was expanded in vivo using IL-2 and IL-2c compared to TRALI mice, as was confirmed through analysis of the spleen, blood, and lung.

CONCLUSION

This study validates that the protective mechanisms against TRALI involve CD4⁺ CD25⁺ FoxP3⁺ Tregs, which can be expanded in vivo by IL-2 and IL-2c. This results in increased IL-10 levels and decreased IL-17A, thereby prophylactically preventing antibody-mediated murine TRALI.

Autologous Hematopoietic Stem Cell Transplantation for Autoimmune Diseases: From Mechanistic Insights to Biomarkers

Phase I/II clinical trials of autologous hematopoietic stem cell transplantation (AHSCT) have led to increased safety and efficacy of this therapy for severe and refractory autoimmune diseases (AD). Recent phase III randomized studies have demonstrated that AHSCT induces long-term disease remission in most patients without any further immunosuppression, with superior efficacy when compared to conventional treatments. Immune monitoring studies have revealed the regeneration of a self-tolerant T and B cell repertoire, enhancement of immune regulatory mechanisms, and changes toward an anti-inflammatory milieu in patients that are responsive to AHSCT. However, some patients reactivate the disease after transplantation due to reasons not yet completely understood. This scenario emphasizes that additional specific immunological interventions are still required to improve or sustain therapeutic efficacy of AHSCT in patients with AD. Here, we critically review the current knowledge about the operating immune mechanisms or established mechanistic biomarkers of AHSCT for AD. In addition, we suggest recommendations for future immune monitoring studies and biobanking to allow discovery and development of biomarkers. In our view, AHSCT for AD has entered a new era and researchers of this field should work to identify robust predictive, prognostic, treatment-response biomarkers and to establish new guidelines for immune monitoring studies and combined therapeutic interventions to further improve the AHSCT protocols and their therapeutic efficacy.

Overexpression of programmed cell death-1 and human leucocyte antigen-DR on circulatory regulatory T cells in out-of-hospital cardiac arrest patients in the early period after return of spontaneous circulation

AIM

Whether regulatory T cells (Tregs) are involved in immune disorders of out-of-hospital cardiac arrest (OHCA) patients after return of spontaneous circulation (ROSC) is still unknown. We aimed to observe the expression of circulatory Tregs in OHCA patients and investigate programmed cell death-1 (PD-1) and human leucocyte antigen-DR (HLA-DR) on Tregs to evaluate the induction and activity of Tregs.

METHODS

Sixty-seven consecutive OHCA patients who recovered from spontaneous circulation over 12 h were enrolled. Clinical and 28-day outcome data were collected. Peripheral blood samples collected on days 1 and 3 after ROSC were analysed to evaluate PD-1 and HLA-DR expression on Tregs. Fifty healthy individuals were enrolled as healthy controls.

RESULTS

Compared with those in healthy individuals, circulatory Treg counts significantly decreased without changes of Treg/cluster-of-differentiation (CD)4+ lymphocyte ratios on day 1 after ROSC, and the percentage of PD-1+ Tregs and HLA-DR+ Tregs significantly rose. On day 3, Treg/CD4+ lymphocyte ratios rose with persistently low Treg counts, and the expression of PD-1 and HLA-DR on Tregs was not different from that on day 1. On day 1, both circulatory Treg counts and Treg/CD4+ lymphocyte ratios in non-survivors were lower than those in survivors, and Treg/CD4+ lymphocyte ratios increased in non-survivors on day 3. No significant difference of PD-1 and HLA-DR expression on Tregs was found between survivors and non-survivors on day 1.

CONCLUSIONS

After ROSC, despite decreased circulatory Treg counts, a relative increase of Treg percentage and enhanced activity of Tregs are involved in early immune regulation of OHCA patients.

Immunoregulatory Effects of Myeloid-Derived Suppressor Cell Exosomes in Mouse Model of Autoimmune Alopecia Areata

The treatment of autoimmune diseases still poses a major challenge, frequently relying on non-specific immunosuppressive drugs. Current efforts aim at reestablishing self tolerance using immune cells with suppressive activity like the regulatory T cells (Treg) or the myeloid-derived suppressor cells (MDSC). We have demonstrated therapeutic efficacy of MDSC in mouse Alopecia Areata (AA). In the same AA model, we now asked whether MDSC exosomes (MDSC-Exo) can replace MDSC. MDSC-Exo from bone marrow cells (BMC) cultures of healthy donors could substantially facilitate treatment. With knowledge on MDSC-Exo being limited, their suitability needs to be verified in advance. Protein marker profiles suggest comparability of BMC- to ex vivo collected inflammatory MDSC/MDSC-Exo in mice with a chronic contact dermatitis, which is a therapeutic option in AA. Proteome analyses substantiated a large overlap of function-relevant molecules in MDSC and MDSC-Exo. Furthermore, MDSC-Exo are taken up by T cells, macrophages, NK, and most avidly by Treg and MDSC-Exo uptake exceeds binding of MDSC themselves. In AA mice, MDSC-Exo preferentially target skin-draining lymph nodes and cells in the vicinity of remnant hair follicles. MDSC-Exo uptake is accompanied by a strong increase in Treg, reduced T helper proliferation, mitigated cytotoxic activity, and a slight increase in lymphocyte apoptosis. Repeated MDSC-Exo application in florid AA prevented progression and sufficed for partial hair regrowth. Deep sequencing of lymphocyte mRNA from these mice revealed a significant increase in immunoregulatory mRNA, including FoxP3 and arginase 1. Downregulated mRNA was preferentially engaged in prohibiting T cell hyperreactivity. Taken together, proteome analysis provided important insights into potential MDSC-Exo activities, these Exo preferentially homing into AA-affected organs. Most importantly, changes in leukocyte mRNA seen after treatment of AA mice with MDSC-Exo sustainably supports the strong impact on the adaptive and the non-adaptive immune system, with Treg expansion being a dominant feature. Thus, MDSC-Exo could potentially serve as therapeutic agents in treating AA and other autoimmune diseases.

Janus-Faced Myeloid-Derived Suppressor Cell Exosomes for the Good and the Bad in Cancer and Autoimmune Disease

Myeloid-derived suppressor cells (MDSCs) are a heterogeneous population of immature myeloid cells originally described to hamper immune responses in chronic infections. Meanwhile, they are known to be a major obstacle in cancer immunotherapy. On the other hand, MDSC can interfere with allogeneic transplant rejection and may dampen autoreactive T cell activity. Whether MDSC-Exosomes (Exo) can cope with the dangerous and potentially therapeutic activities of MDSC is not yet fully explored. After introducing MDSC and Exo, it will be discussed, whether a blockade of MDSC-Exo could foster the efficacy of immunotherapy in cancer and mitigate tumor progression supporting activities of MDSC. It also will be outlined, whether application of native or tailored MDSC-Exo might prohibit autoimmune disease progression. These considerations are based on the steadily increasing knowledge on Exo composition, their capacity to distribute throughout the organism combined with selectivity of targeting, and the ease to tailor Exo and includes open questions that answers will facilitate optimizing protocols for a MDSC-Exo blockade in cancer as well as for strengthening their therapeutic efficacy in autoimmune disease.

Engineered Tolerance: Tailoring Development, Function, and Antigen-Specificity of Regulatory T Cells

Regulatory T cells (Tregs) are potent suppressors of immune responses and are currently being clinically tested for their potential to stop or control undesired immune responses in autoimmunity, hematopoietic stem cell transplantation, and solid organ transplantation. Current clinical approaches aim to boost Tregs in vivo either by using Treg-promoting small molecules/proteins and/or by adoptive transfer of expanded Tregs. However, the applicability of Treg-based immunotherapies continues to be hindered by technical limitations related to cell isolation and expansion of a pure, well-characterized, and targeted Treg product. Efforts to overcome these limitations and improve Treg-directed therapies are now under intense investigation in animal models and pre-clinical studies. Here, we review cell and protein engineering-based approaches that aim to target different aspects of Treg biology including modulation of IL-2 signaling or FOXP3 expression, and targeted antigen-specificity using transgenic T cell receptors or chimeric antigen receptors. With the world-wide interest in engineered T cell therapy, these exciting new approaches have the potential to be rapidly implemented and developed into therapies that can effectively fine-tune immune tolerance.

Immunoregulatory effects of 4-(4-chlorophenyl)-1-(5-amino-3-methylisoxazole-4-carbonyl)-thiosemicarbazide (06K) in non-immunized and SRBC-immunized mice

OBJECTIVES

Immunoregulatory properties of 06K derivative (4-(4-chlorophenyl)-1-(5-amino-3-methylisoxazole-4-carbonyl)-thiosemicarbazide) in mouse in vivo models were investigated.

METHODS

Several in vivo models were used: humoral and cellular immune response, carrageenan inflammatory reaction and determination of lymphocyte subsets in non-immunized mice.

KEY FINDINGS

The compound administered before or after immunization with sheep erythrocytes (sheep red blood cell (SRBC)) elevated the number of plaque-forming cells (PFC), and this effect was stronger at lower doses. Although total haemagglutinin titres to SRBC decreased upon postimmunization treatment, IgG titre increased. In the model of delayed-type hypersensitivity (DTH) to ovalbumin (OVA), the compound, applied intraperitoneally before an eliciting dose of an antigen but not before immunization, inhibited the magnitude of a cutaneous reaction. Further, 06K significantly diminished carrageenan-induced foot pad inflammation when administered 1 h before carrageenan. The compound, administered intraperitoneally to naïve mice, elicited changes in weight, cell number in lymphoid organs and content of lymphocyte subsets, depending on the dose and number of applications. Phenotypic changes included increased turnover of thymocytes, changes in B-cell distribution in spleens and lymph nodes, increased percentage of CD8⁺ cells and regulatory CD4⁺ CD25⁺ Foxp3⁺ T cells.

CONCLUSIONS

Immunoregulatory properties of 06K involve mobilization of lymphopoiesis and generation of regulatory T cells.

Therapeutic anti-CD3 monoclonal antibodies: from bench to bedside

The induction of tolerance is a major goal of immunotherapy. Investigations over the last 20 years have shown that anti-CD3 monoclonal antibodies (mAbs) effectively treat autoimmune disease in animal models and have also shown promise in clinical trials. Tolerance induction by anti-CD3 mAbs is related to the induction of Tregs that control pathogenic autoimmune responses. Here, we review preclinical and clinical studies in which intravenous or mucosal administration of anti-CD3 mAbs has been employed and provide an outlook on future developments to enhance the efficacy of this promising therapeutic approach.

Changes in Immunogenicity during the Development of Urinary Bladder Cancer: A Preliminary Study

In the present study, we evaluated tumor-infiltrating lymphocytes (TILs) and blood regulatory T lymphocyte (Tregs, CD4+/CD25+/FoxP3+) expression in bladder cancer patients. The number of CD4+, CD8+, CD25+, FoxP3+ and CD20+ TILs was analyzed in association with clinico-pathomorphological features. In more advanced metastasizing tumors, showing non-classic differentiation (ND) and a more aggressive tissue invasion type (TIT), the number of TILs decreased. A low number of CD4+ TILs was associated with poor prognosis. Similarly, Treg frequency before surgery and after surgical treatment was significantly lower in more advanced tumors. The changes in TILs, as well as of local and systemic Tregs, were accompanied by changes in the histological phenotype of urothelial carcinoma regarding pT stage, NDs, TIT, and clinical outcomes. The number of TILs and the frequency of blood Tregs (indicators of antitumor response) may be essential for choosing an immunotherapy that is adjusted to the immune status according to the phase of tumor growth. Moreover, a significant reduction in the number of CD4+ and CD8+ TILs with the development of NDs in more advanced tumors may be associated with lower tumor immunogenicity, resulting in immune tolerance towards tumor tissue. These observations and the tendency of urothelial bladder carcinoma to undergo NDs in a heterogeneous manner during tumor progression suggest complex interactions between bladder cancer immunogenicity and stages of tumor progression.