Regulatory T Cells in Immunologic Self-Tolerance and Autoimmune Disease

Enhancing pancreatic cancer immunotherapy: Leveraging localized delivery strategies through the use of implantable devices and scaffolds

Pancreatic cancer (PC) remains the predominant type of upper gastrointestinal tract cancer, associated with heightened morbidity and a survival rate below 12%. While immunotherapy has brought about transformative changes in the standards of care for most solid tumors, its application in PC is hindered by the ''cold tumor'' microenvironment, marked by the presence of immunosuppressive cells. Modest response rates in PC are attributed, in part to, the fibrotic stroma that obstructs the delivery of systemic immunotherapy. Furthermore, the occurrence of immune-related adverse events (iRAEs) often necessitates the use of sub-therapeutic doses or treatment discontinuation. In the pursuit of innovative approaches to enhance the effectiveness of immunotherapy for PC, implantable drug delivery devices and scaffolds emerge as promising strategies. These technologies offer the potential for sustained drug delivery directly to the tumor site, overcoming stromal barriers, immunosuppression, T cell exclusion, immunotherapy resistance, optimizing drug dosage, and mitigating systemic toxicity. This review offers a comprehensive exploration of pancreatic ductal adenocarcinoma (PDAC), the most common and aggressive form of PC, accompanied by a critical analysis of the challenges the microenvironment presents to the development of successful combinational immunotherapy approaches. Despite efforts, these approaches have thus far fallen short in enhancing treatment outcomes for PDAC. The review will subsequently delve into the imperative need for refining delivery strategies, providing an examination of past and ongoing studies in the field of localized immunotherapy for PDAC. Addressing these issues will lay the groundwork for the development of effective new therapies, thereby enhancing treatment response, patient survival, and overall quality of life for individuals diagnosed with PDAC.

Immune interplay from circulation to local lesion in pemphigus pathogenesis

Pemphigus, a potentially lethal autoimmune skin disease, is mediated by desmoglein-specific antibodies, manifesting cutaneous and mucosal blisters and erosions. The interaction between multiple immune counterparts contributes to the progress of pemphigus. Currently, the emergence of bioinformatic analysis enables investigators to gain a global picture of the pemphigus immune network, based on the exhaustive pedigree annotation of multiple subsets. T helper subsets dominate the landscape as mentioned previously, and innate immune cells have been involved as well. Of particular interests is which phenotype of T cells orchestrates the autoimmune process and chronic inflammation in a certain condition. In this review, the circulatory and peripheral immune cells and cytokine components constituting the immune microenvironment are separately discussed to provide a perspective on pemphigus pathogenesis, with particular reference to insights provided by the bioinformation technique.

Peroxynitrite reduces Treg cell expansion and function by mediating IL-2R nitration and aggravates multiple sclerosis pathogenesis: One sentence summary: Peroxynitrite-mediated Treg IL-2R nitration impacts on multiple sclerosis

T-helper 17 cells and regulatory T cells (Treg) are critical regulators in the pathogenesis of multiple sclerosis (MS) but the factors affecting Treg/Th17 balance remains largely unknown. Redox balance is crucial to maintaining immune homeostasis and reducing the severity of MS but the underlying mechanisms are unclear yet. Herein, we tested the hypothesis that peroxynitrite, a representative molecule of reactive nitrogen species (RNS), could inhibit peripheral Treg cells, disrupt Treg/Th17 balance and aggravate MS pathology by inducing nitration of interleukin-2 receptor (IL-2R) and down-regulating RAS/JNK-AP-1 signalling pathway. Experimental autoimmune encephalomyelitis (EAE) mouse model and serum samples of MS patients were used in the study. We found that the increases of 3-nitrotyrosine and IL-2R nitration in Treg cells were coincided with disease severity in the active EAE mice. Mechanistically, peroxynitrite-induced IL-2R nitration down-regulated RAS/JNK signalling pathway, subsequently impairing peripheral Treg expansion and function, increasing Teff infiltration into the central nerve system (CNS), aggravating demyelination and neurological deficits in the EAE mice. Those changes were abolished by peroxynitrite decomposition catalyst (PDC) treatment. Furthermore, transplantation of the PDC-treated-autologous Treg cells from donor EAE mice significantly decreased Th17 cells in both axillary lymph nodes and lumbar spinal cord, and ameliorated the neuropathology of the recipient EAE mice. Those results suggest that peroxynitrite could disrupt peripheral Treg/Th17 balance, and aggravate neuroinflammation and neurological deficit in active EAE/MS pathogenesis. The underlying mechanisms are related to induce the nitration of IL-2R and inhibit the RAS/JNK-AP-1 signalling pathway in Treg cells. The study highlights that targeting peroxynitrite-mediated peripheral IL-2R nitration in Treg cells could be a novel therapeutic strategy to restore Treg/Th17 balance and ameliorate MS/EAE pathogenesis. The study provides valuable insights into potential role of peripheral redox balance in maintaining CNS immune homeostasis.

Anti-inflammatory role of APRIL by modulating regulatory B cells in antigen-induced arthritis

APRIL (A Proliferation-Inducing Ligand), a member of the TNF superfamily, was initially described for its ability to promote proliferation of tumor cells in vitro. Moreover, this cytokine has been related to the pathogenesis of different chronic inflammatory diseases, such as rheumatoid arthritis. This study aimed to evaluate the ability of APRIL in regulating B cell-mediated immune response in the antigen-induced arthritis (AIA) model in mice. AIA was induced in previously immunized APRIL-transgenic (Tg) mice and their littermates by administration of antigen (mBSA) into the knee joints. Different inflammatory cell populations in spleen and draining lymph nodes were analyzed using flow cytometry and the assay was performed in the acute and chronic phases of the disease, while cytokine levels were assessed by ELISA. In the acute AIA, APRIL-Tg mice developed a less severe condition and a smaller inflammatory infiltrate in articular tissues when compared with their littermates. We also observed that the total cellularity of draining lymph nodes was decreased in APRIL-Tg mice. Flow cytometry analysis revealed an increase of CD19+IgM+CD5+ cell population in draining lymph nodes and an increase of CD19+CD21hiCD23hi (B regulatory) cells in APRIL-Tg mice with arthritis as well as an increase of IL-10 and CXCL13 production in vitro.

New cell sources for CAR-based immunotherapy

Chimeric antigen receptor (CAR) T cell therapy, in which a patient's own T lymphocytes are engineered to recognize and kill cancer cells, has achieved striking success in some hematological malignancies in preclinical and clinical trials, resulting in six FDA-approved CAR-T products currently available in the market. Despite impressive clinical outcomes, concerns about treatment failure associated with low efficacy or high cytotoxicity of CAR-T cells remain. While the main focus has been on improving CAR-T cells, exploring alternative cellular sources for CAR generation has garnered growing interest. In the current review, we comprehensively evaluated other cell sources rather than conventional T cells for CAR generation.

Expansion and characterization of regulatory T cell populations from Korean kidney transplant recipients

The development of immunosuppressants has enabled remarkable progress in kidney transplantation (KT). However, current immunosuppressants cannot induce immune tolerance, and their nonspecific immunosuppressive effects result in many adverse effects. Regulatory T cells (Tregs) play crucial roles in controlling all specific immune responses. This study evaluated the distribution of Tregs and their effects on kidney allograft function in Korean KT recipients. We enrolled 113 KT recipients with stable graft function. The differentiation and expansion of Tregs were examined by flow cytometry to compare the Tregs subpopulations. Among the 113 patients, 73 (64.6%) were males, and the mean follow-up period from KT to Tregs collection was 147.5 + 111.3 months. Patients receiving lower doses of cyclosporine had higher proportions of Tregs than those with higher doses of cyclosporine (36.3 + 21.6 vs 17.0 + 12.7, P = .010, respectively). Patients taking cyclosporine tended to have higher Tregs numbers than those taking tacrolimus (94.7 + 158.1 vs 49.3 + 69.4, P = .095, respectively). However, no significant association was observed between Tregs and allograft dysfunction in the cox proportional hazard model. Tregs counts may be associated with the type and dose of immunosuppressants. However, no significant relationship was found between Tregs and kidney allograft function in stable KT recipients.

Effects of immunosuppressants on T-cell dynamics: Understanding from a generic coarse-grained immune network model

Long-term immunosuppressive therapy is a drug regimen often used to lower aggressive immune responses in various chronic inflammatory diseases. However, such long-term therapy leading to immune suppression may trigger other adverse reactions in the immune system. The rising concern regarding the optimal dose and duration of such treatment has motivated us to understand non-classical immunomodulatory responses induced by various immunosuppressive steroid and secosteroid drugs such as glucocorticoid and vitamin D supplements. The immunomodulatory actions of such immunosuppressants (that govern the adaptive immune response) are often mediated through their characteristic control over CD4+ T-cells involving pro- and antiinflammatory T-cells. Several early studies attempted to decode temporal and dose-dependent behaviors of such pro- and anti-inflammatory T-cells using the chemical dynamics approach. We first summarize these early works. Then, we develop a minimal coarse-grained kinetic network model to capture the commonality in their immunomodulatory functions. This generic model successfully reproduces the characteristic dynamical features, including the clinical latency period in long-term T-cell dynamics. The temporal behavior of T-cells is found to be sensitive to specific rate parameters and doses of immunosuppressants. The steady-state analysis reflects the transition from an early classified weakly regulated (autoimmune-prone) immune state to a strongly regulated state (immunocompromised state), separated by an intervening state of moderate/balanced regulation. An optimal dose and duration are essential in rescuing balanced immune regulation. This review elucidates how developing a simple generic coarse-grained immune network model may provide immense information that helps diagnose inefficacy in adaptive immune function before and after administering immunosuppressants such as glucocorticoid or vitamin D.

Investigation of the impact of SARS-CoV infection on the immunologic status and lung function after 15 years

BACKGROUND

We investigate the long-term effects of SARS-CoV on patients' lung and immune systems 15 years post-infection. SARS-CoV-2 pandemic is ongoing however, another genetically related beta-coronavirus SARS-CoV caused an epidemic in 2003-2004.

METHODS

We enrolled 58 healthcare workers from Peking University People's Hospital who were infected with SARS-CoV in 2003. We evaluated lung damage by mMRC score, pulmonary function tests, and chest CT. Immune function was assessed by their serum levels of globin, complete components, and peripheral T cell subsets. ELISA was used to detect SARS-CoV-specific IgG antibodies in sera.

RESULTS

After 15 years of disease onset, 19 (36.5%), 8 (34.6%), and 19 (36.5%) subjects had impaired DL (CO), RV, and FEF25-75, respectively. 17 (30.4%) subjects had an mMRC score ≥ 2. Fourteen (25.5%) cases had residual CT abnormalities. T regulatory cells were a bit higher in the SARS survivors. IgG antibodies against SARS S-RBD protein and N protein were detected in 11 (18.97%) and 12 (20.69%) subjects, respectively. Subgroup analysis revealed that small airway dysfunction and CT abnormalities were more common in the severe group than in the non-severe group (57.1% vs 22.6%, 54.5% vs 6.1%, respectively, p < 0.05).

CONCLUSIONS

SARS-CoV could cause permanent damage to the lung, which requires early pulmonary rehabilitation. The long-lived immune memory response against coronavirus requires further studies to assess the potential benefit. Trial registration ClinicalTrials.gov, NCT03443102. Registered prospectively on 25 January 2018.

Immune phase transition under steroid treatment

The steroid hormone glucocorticoid (GC) is a well-known immunosuppressant that controls T-cell-mediated adaptive immune response. In this work, we have developed a minimal kinetic network model of T-cell regulation connecting relevant experimental and clinical studies to quantitatively understand the long-term effects of GC on pro-inflammatory T-cell (T_{pro}) and anti-inflammatory T-cell (T_{anti}) dynamics. Due to the antagonistic relation between these two types of T cells, their long-term steady-state population ratio helps us to characterize three classified immune regulations: (i) weak ([T_{pro}]>[T_{anti}]), (ii) strong ([T_{pro}]<[T_{anti}]), and (iii) moderate ([T_{pro}]∼[T_{anti}]), holding the characteristic bistability. In addition to the differences in their long-term steady-state outcome, each immune regulation shows distinct dynamical phases. In the presteady state, a characteristic intermediate stationary phase is observed to develop only in the moderate regulation regime. In the medicinal field, the resting time in this stationary phase is distinguished as a clinical latent period. GC dose-dependent steady-state analysis shows an optimal level of GC to drive a phase transition from the weak or autoimmune prone to the moderate regulation regime. Subsequently, the presteady state clinical latent period tends to diverge near that optimal GC level where [T_{pro}]:[T_{anti}] is highly balanced. The GC-optimized elongated stationary phase explains the rationale behind the requirement of long-term immune diagnostics, especially when long-term GC-based chemotherapeutics and other immunosuppressive drugs are administrated. Moreover, our study reveals GC sensitivity of clinical latent period, which might serve as an early warning signal in diagnosing different immune phases and determining immune phasewise steroid treatment.

Ex Vivo-Induced Bone Marrow-Derived Myeloid Suppressor Cells Prevent Corneal Allograft Rejection in Mice

Purpose

To investigate the effects of ex vivo-induced bone marrow myeloid-derived suppressor cells (BM-MDSCs) on allogeneic immune responses in corneal transplantation.

Methods

Bone marrow cells from C57BL/6J (B6) mice were cultured with IL-6 and GM-CSF for four days. The ex vivo induction of the BM-MDSCs was assessed using flow cytometry, inducible nitric oxide synthase (iNOS) mRNA expression using reverse transcription-quantitative polymerase chain reaction, and nitric oxide (NO) production in allogeneic stimulation. T-cell proliferation and regulatory T-cell (Treg) expansion were investigated on allogeneic stimulation in the presence of ex vivo-induced BM-MDSCs. IFN-γ, IL-2, IL-10, and TGF-β1 protein levels were measured using enzyme-linked immunosorbent assays. After subconjunctival injection of ex vivo-induced BM-MDSCs, the migration of the BM-MDSCs into corneal grafts, allogeneic corneal graft survival, neovascularization, and lymphangiogenesis were assessed using flow cytometry, slit-lamp microscopy, and immunohistochemistry.

Results

The combination of GM-CSF and IL-6 significantly induced BM-MDSCs with increased iNos mRNA expression. The ex vivo-induced BM-MDSCs promoted NO release in allogeneic stimulation in vitro. The ex vivo-induced BM-MDSCs inhibited T-cell proliferation and promoted Treg expansion. Decreased IFN-γ and increased IL-2, IL-10, and TGF-β1 production was observed in coculture of ex vivo-induced BM-MDSCs. Injected ex vivo-induced BM-MDSCs were confirmed to migrate into the grafts. The injected BM-MDSCs also prolonged corneal graft survival and prevented angiogenesis and lymphangiogenesis.

Conclusions

The ex vivo-induced BM-MDSCs have suppressive effects on allogeneic immune responses and prolong corneal allograft survival via the iNOS pathway, indicating that they may be a potential therapeutic tool for corneal transplantation.

Successful Treatment of Steroid-Refractory Checkpoint Inhibitor Myocarditis with Globulin Derived-Therapy: A case report and literature review

Immune checkpoint inhibitor (ICI) monoclonal antibody drugs are an important interface of immunology and cancer biology with the intended goal to create cancer specific treatments with less systemic toxicity. Recognition of immune-related adverse events is critical and these include significant cardiovascular toxicity and myocarditis. Compared with other immune-related events, ICI associated myocarditis is rare but is associated with high mortality. The majority of cases present early in the course of therapy and patients can rapidly progress to fulminant myocarditis. Initially, the mainstay of treatment in patients with ICI-associated myocarditis is immunosuppressive therapy with glucocorticoids. For those who do not respond to steroids, the optimal treatment is unclear. This review summarizes the potential adjunctive treatment options for patients with steroid-refractory myocarditis by illustrating a case of myocarditis that was treated with Thymoglobulin and immunoglobulin.

Changes in Blood Metabolites and Immune Cells in Holstein and Jersey Dairy Cows by Heat Stress

Simple Summary

As global temperatures rise, thermal stress can be a major problem affecting cows. If they are subjected to heat stress, they are likely to exhibit abnormal metabolic reactions and affect their immune system. However, the relationship between metabolism and immunity during thermal stress and these crosstalk mechanisms remain unclear. Therefore, the aim of this study was to understand the changes in blood immune cell response with the physiological metabolism changes of Holstein and Jersey cows through the biochemistry and flow cytometry branches under thermal stress conditions. We found that various blood metabolites were reduced in both Holsteins and Jerseys by heat stress conditions. There were breed-specific variations in the immune cell population in Holstein and Jersey cows under different environmental conditions. The main findings of this study provide information on the metabolism and immunity changes of two types of cow under heat stress, broadening the potential relationship of these changes.

Abstract

Owing to increasing global temperatures, heat stress is a major problem affecting dairy cows, and abnormal metabolic responses during heat stress likely influence dairy cow immunity. However, the mechanism of this crosstalk between metabolism and immunity during heat stress remains unclear. We used two representative dairy cow breeds, Holstein and Jersey, with distinct heat-resistance characteristics. To understand metabolic and immune responses to seasonal changes, normal environmental and high-heat environmental conditions, we assessed blood metabolites and immune cell populations. In biochemistry analysis from sera, we found that variety blood metabolites were decreased in both Holstein and Jersey cows by heat stress. We assessed changes in immune cell populations in peripheral blood mononuclear cells (PBMCs) using flow cytometry. There were breed-specific differences in immune-cell population changes. Heat stress only increased the proportion of B cells (CD4–CD21+) and heat stress tended to decrease the proportion of monocytes (CD11b+CD172a+) in Holstein cows. Our findings expand the understanding of the common and specific changes in metabolism and immune response of two dairy cow breeds under heat stress conditions.

Toward Regulatory Effects of Curcumin on Transforming Growth Factor-Beta Across Different Diseases: A Review

Immune response, proliferation, migration and angiogenesis are juts a few of cellular events that are regulated by transforming growth factor-β (TGF-β) in cells. A number of studies have documented that TGF-β undergoes abnormal expression in different diseases, e.g., diabetes, cancer, fibrosis, asthma, arthritis, among others. This has led to great fascination into this signaling pathway and developing agents with modulatory impact on TGF-β. Curcumin, a natural-based compound, is obtained from rhizome and roots of turmeric plant. It has a number of pharmacological activities including antioxidant, anti-inflammatory, anti-tumor, anti-diabetes and so on. Noteworthy, it has been demonstrated that curcumin affects different molecular signaling pathways such as Wnt/β-catenin, Nrf2, AMPK, mitogen-activated protein kinase and so on. In the present review, we evaluate the potential of curcumin in regulation of TGF-β signaling pathway to corelate it with therapeutic impacts of curcumin. By modulation of TGF-β (both upregulation and down-regulation), curcumin ameliorates fibrosis, neurological disorders, liver disease, diabetes and asthma. Besides, curcumin targets TGF-β signaling pathway which is capable of suppressing proliferation of tumor cells and invading cancer cells.

Ex vivo expansion of regulatory T cells from abdominal aortic aneurysm patients inhibits aneurysm in humanized murine model

OBJECTIVE

Abdominal aortic aneurysm (AAA) is a chronic inflammatory disease. Studies of human aneurysm tissue demonstrate dense inflammatory cell infiltrates with CD4+ T cells predominating. Regulatory T cells (Tregs) play an important role in inhibiting pro-inflammatory T cell proliferation, therefore, limiting collateral tissue destruction. The aim of this study was to investigate whether ex vivo augmentation of human Tregs attenuates aneurysm formation in humanized murine model of AAA.

METHODS

Circulating Treg population in AAA patients and age- and gender-matched controls were determined by real-time polymerase chain reaction and flow cytometry. To create humanized murine model of AAA, irradiated Rag1-deficient (Rag1-/-) mice, without mature T lymphocytes, at 7 weeks of age were given 5 × 106 of human CD4+ T cells intraperitoneally. Then the mice underwent CaCl2 aneurysm induction. Aortic diameters were measured before and at 6 weeks after aneurysm induction. Aortic tissue was collected for histology and protein extraction. Verhoeff-Van Gieson stain was used for staining elastic fiber. CD4+ T cells in the aortic tissue were detected by immunohistochemical staining.

RESULTS

In human peripheral blood mononuclear cells, the proportion of Tregs are decreased in AAA patients compared with matched control patients with significant vascular disease. We first validated the role of Tregs in the CaCl2 model of AAA. To determine the role of human T cells in AAA formation, Rag1-/- mice, resistant to CaCl2-aneurysm induction, were transplanted with human CD4+ T cells. Human CD4+ T cells were able to drive aneurysm formation in Rag1-/- mice. We show that ex vivo augmentation of human Tregs by interleukin-2 resulted in decreased aneurysm progression.

CONCLUSIONS

These data suggest that the ex vivo expansion of human Tregs may be a potential therapeutic strategy for inhibiting progression of AAA.

Influence of single gene variants of FOXP3 on allergic asthma predisposition

BACKGROUND

The role of FoxP3, a master regulator of T regulatory cells, in allergic diseases such as asthma is of immense importance yet the effect of its gene variants on the disease predisposition is not fully understood. We studied the association of FoxP3 polymorphisms (-2383C/T and -3279C/A) in allergic asthma patients and their correlation with serum IL-4, IL-13, Total IgE, and Vitamin D levels.

METHODS

In this study 350 individuals were enrolled, 150 allergic asthma patients and 200 healthy controls. SNP analyses were performed by RFLP. IL-4, IL-13 vitamin D and Total IgE were measured by ELISA.

RESULTS

The AA homozygous mutant of -3279C/A posed a three-fold risk [P < 0.005; OR, 3.52] whereas the -2383C/T variants TT genotype carried a fourfold risk [P = 0.002; OR, 4.04]. Haplotype analysis exhibited predisposition to allergic asthmawith CC/TT [P = 0.01; OR 5.93 (95%CI)], AA/CC [P = 0.01; OR 3.29] and AA/TT haplotypes [P = 0; OR 11.86 (1.31-85.87)]. A negative correlation between IgE and Vitamin D was found [r = -0.30p-value 0.001] but a negative correlation betweenIgE and Vit D was established in the haplotype CC/TT [r = -0.45P = 0.002] and CC/CT [r = -0.52P = 0.04]. In allergic patients, the eosinophils count was high [p = 0.003] and the mean levels of pro-inflammatory cytokines IL-4 and IL-13 were elevated [P < 0.001] as well.

CONCLUSIONS

The study suggests SNP -3279 -AA genotype and, -2383-TT genotype in association with certain haplotypes pose a risk for allergy development. There was no correlation between different genotypes and serum levels of various cytokines.

Engineered biomaterials for cancer immunotherapy

Although cancer immunotherapy is showing tremendous promise and has progressed to the clinic, it has only achieved sporadic efficacy, with only a fraction of patients benefitting from the therapy and with undesirable side effects due to poor selectivity and high doses. Localized delivery of immunomodulators to activate anticancer immunity in situ avoids overactivation of the systemic immune system and reduces side effects. Engineered biomaterials-implantable, injectable, or transdermal-fabricated into drug delivery devices are critical components for the development of localized cancer immunotherapies. In this review, we briefly summarize progress in the application of engineered biomaterials to the localized delivery of cancer immunotherapy.

Increased proportion of functional subpopulations in circulating regulatory T cells in patients with chronic hepatitis B

AIM

This study was designed to investigate the levels of circulating regulatory T cells (Tregs), and their functional subpopulations and related cytokines in chronic hepatitis B patients (CHB) and inactive hepatitis B surface antigen carriers.

METHODS

The peripheral blood of 24 hepatitis B virus inactive carriers, 26 CHB patients, and 34 healthy controls was collected and analyzed by flow cytometry for Tregs and CD4⁺ CXCR5⁺ FoxP3⁺ follicular regulatory T cells. Interleukin (IL)-10, transforming growth factor-β, and IL-21 levels in plasma were determined by enzyme-linked immunosorbent assay. Proportions of functional Treg subpopulations were analyzed by staining of Helios, CD45RA and FoxP3, TIGIT, and CD226, and the correlations between Treg subsets and clinical indicators were explored.

RESULTS

CD4⁺ FoxP3⁺ levels in the peripheral blood of CHB patients were significantly increased, and the inhibitory ability of Tregs in CHB patients for cytokine secretion was stronger, and CD4⁺ CXCR5⁺ FoxP3⁺ follicular Tregs were also significantly higher than inactive carriers and healthy controls. Transforming growth factor-β and IL-10 in the plasma of CHB patients were significantly higher than those of healthy controls, with IL-21 levels not significantly changed. Circulating CD4⁺ CXCR5-FoxP3⁺ Treg cells in CHB patients were positively correlated with hepatitis B surface antigen, hepatitis B e antigen, and hepatitis B virus DNA. The proportions of Helios⁺ FoxP3⁺ , CD45RA^- FoxP3^hi , and CD226^- TIGIT⁺ functional subpopulations in CD4⁺ CXCR5^- FoxP3⁺ Tregs in CHB patients were significantly increased, and they were significantly correlated with clinical indicators.

CONCLUSIONS

Circulating Tregs in CHB patients not only have elevated levels, but their follicular Treg subpopulations are also increased, and Tregs tend to have stronger immunosuppressive functions.

Rebalancing Immune Homeostasis to Treat Autoimmune Diseases

During homeostasis, interactions between tolerogenic dendritic cells (DCs), self-reactive T cells, and T regulatory cells (Tregs) contribute to maintaining mammalian immune tolerance. In response to infection, immunogenic DCs promote the generation of proinflammatory effector T cell subsets. When complex homeostatic mechanisms maintaining the balance between regulatory and effector functions become impaired, autoimmune diseases can develop. We discuss some of the newest advances on the mechanisms of physiopathologic homeostasis that can be employed to develop strategies to restore a dysregulated immune equilibrium. Some of these designs are based on selectively activating regulators of immunity and inflammation instead of broadly suppressing these processes. Promising approaches include the use of nanoparticles (NPs) to restore Treg control over self-reactive cells, aiming to achieve long-term disease remission, and potentially to prevent autoimmunity in susceptible individuals.

Autoantibodies in lung transplantation

Chronic lung allograft dysfunction (CLAD) comprises both bronchiolitis obliterans syndrome and restrictive allograft syndrome as subtypes. After lung transplantation, CLAD remains a major limitation for long-term survival, and lung transplant recipients therefore have poorer outcomes compared with recipients of other solid organ transplants. Although the number of lung transplants continues to increase globally, the field demands detailed understanding of immunoregulatory mechanisms and more effective individualized therapies to combat CLAD. Emerging evidence suggests that CLAD is multifactorial and involves a complex, delicate interplay of multiple factors, including perioperative donor characteristics, inflammation induced immediately following transplant, post-transplant infection and interplay between allo- and autoimmunity directed to donor antigens. Recently, identification of stress-induced exosome release from the transplanted organ has emerged as an underlying mechanism in the development of chronic rejection and promises to prompt novel strategies for future therapeutic interventions. In this review, we will discuss recent studies and ongoing research into the mechanisms for the development of CLAD, with emphasis on immune responses to lung-associated self-antigens-that is, autoimmunity.

Mesoporous Silica as a Versatile Platform for Cancer Immunotherapy

Immunotherapy has been recognized for decades as a promising therapeutic method for cancer treatment. To enhance host immune responses against cancer, antigen-presenting cells (APCs; e.g., dendritic cells) or T cells are educated using immunomodulatory agents including tumor-associated antigens and adjuvants, and manipulated to induce a cascading adaptive immune response targeting tumor cells. Mesoporous silica materials are promising candidates to improve cancer immunotherapy based on their attractive properties that include high porosity, high biocompatibility, facile surface modification, and self-adjuvanticity. Here, the recent progress on mesoporous-silica-based immunotherapies based on two material forms is summarized: 1) mesoporous silica nanoparticles (MSNs), which can be internalized into APCs, and 2) micrometer-sized mesoporous silica rods (MSRs) that can form a 3D space to recruit APCs. Subcutaneously injected MSN-based cancer vaccines can be taken up by peripheral APCs or by APCs in lymphoid organs to educate the immune system against cancer cells. MSR cancer vaccines can recruit immune cells into the MSR scaffold to induce cancer-specific immunity. Both vaccine systems successfully stimulate the adaptive immune response to eradicate cancer in vivo. Thus, mesoporous silica has potential value as a material platform for the treatment of cancer or infectious diseases.

Experimental Autoimmune Encephalomyelitis (EAE) as Animal Models of Multiple Sclerosis (MS)

Multiple sclerosis (MS) is a multifocal demyelinating disease of the central nervous system (CNS) leading to the progressive destruction of the myelin sheath surrounding axons. It can present with variable clinical and pathological manifestations, which might reflect the involvement of distinct pathogenic processes. Although the mechanisms leading to the development of the disease are not fully understood, numerous evidences indicate that MS is an autoimmune disease, the initiation and progression of which are dependent on an autoimmune response against myelin antigens. In addition, genetic susceptibility and environmental triggers likely contribute to the initiation of the disease. At this time, there is no cure for MS, but several disease-modifying therapies (DMTs) are available to control and slow down disease progression. A good number of these DMTs were identified and tested using animal models of MS referred to as experimental autoimmune encephalomyelitis (EAE). In this review, we will recapitulate the characteristics of EAE models and discuss how they help shed light on MS pathogenesis and help test new treatments for MS patients.

From autoinflammation to autoimmunity: old and recent findings

Autoimmune diseases and autoinflammatory diseases have a number of similar etiopathogenetic and clinical characteristics, including genetic predisposition and recurrent systemic inflammatory flares. The first phase of ADs involves innate immunity: by means of TLRs, autoantigen presentation, B and T cell recruitment and autoantibody synthesis. The second phase involves adaptive immunity, a self-sustaining process in which immune complexes containing nucleic acids and autoantibodies activate self-directed inflammation. The link between autoimmunity and autoinflammation is IL-1ß, which is crucial in connecting the innate immune response due to NLR activation and the adaptive immune responses of T and B cells. In conclusion, although ADs are still considered adaptive immunity-mediated disorders, there is increasing evidence that innate immunity and inflammasomes are also involved. The aim of this review is to highlight the link between the innate and adaptive immune mechanisms involved in autoimmune diseases.

Autoimmune Lymphoproliferative Syndrome-FAS Patients Have an Abnormal Regulatory T Cell (Treg) Phenotype but Display Normal Natural Treg-Suppressive Function on T Cell Proliferation

Objective

Autoimmune lymphoproliferative syndrome (ALPS) with FAS mutation (ALPS-FAS) is a nonmalignant, noninfectious, lymphoproliferative disease with autoimmunity. Given the central role of natural regulatory T cells (nTregs) in the control of lymphoproliferation and autoimmunity, we assessed nTreg-suppressive function in 16 patients with ALPS-FAS.

Results

The proportion of CD25^highCD127^low Tregs was lower in ALPS-FAS patients than in healthy controls. This subset was correlated with a reduced CD25 expression in CD3⁺CD4⁺ T cells from ALPS patients and thus an abnormally low proportion of CD25^highFOXP3⁺ Helios⁺ T cells. The ALPS patients also displayed a high proportion of naïve Treg (FOXP3^lowCD45RA⁺) and an unusual subpopulation (CD4⁺CD127^lowCD15s⁺CD45RA⁺). Despite this abnormal phenotype, the CD25^highCD127^low Tregs’ suppressive function was unaffected. Furthermore, conventional T cells from FAS-mutated patients showed normal levels of sensitivity to Treg suppression.

Conclusion

An abnormal Treg phenotype is observed in circulating lymphocytes of ALPS patients. However, these Tregs displayed a normal suppressive function on T effector proliferation in vitro. This is suggesting that lymphoproliferation observed in ALPS patients does not result from Tregs functional defect or T effector cells insensitivity to Tregs suppression.

Mechanisms of allergen immunotherapy for inhaled allergens and predictive biomarkers

Allergen immunotherapy is effective in patients with IgE-dependent allergic rhinitis and asthma. When immunotherapy is given continuously for 3 years, there is persistent clinical benefit for several years after its discontinuation. This disease-modifying effect is both antigen-specific and antigen-driven. Clinical improvement is accompanied by decreases in numbers of effector cells in target organs, including mast cells, basophils, eosinophils, and type 2 innate lymphoid cells. Immunotherapy results in the production of blocking IgG/IgG₄ antibodies that can inhibit IgE-dependent activation mediated through both high-affinity IgE receptors (FcεRI) on mast cells and basophils and low-affinity IgE receptors (FcεRII) on B cells. Suppression of T_H2 immunity can occur as a consequence of either deletion or anergy of antigen-specific T cells; induction of antigen-specific regulatory T cells; or immune deviation in favor of T_H1 responses. It is not clear whether the altered long-term memory resides within the T-cell or the B-cell compartment. Recent data highlight the role of IL-10-producing regulatory B cells and "protective" antibodies that likely contribute to long-term tolerance. Understanding mechanisms underlying induction and persistence of tolerance should identify predictive biomarkers of clinical response and discover novel and more effective strategies for immunotherapy.

Altered expression of antigen-specific memory and regulatory T-cell subsets differentiate latent and active tuberculosis

Although one-third of the world population is infected with Mycobacterium tuberculosis, only 5-10% of the infected individuals will develop active tuberculosis (TB) disease and the rest will remain infected with no symptoms, known as latent TB infection (LTBI). Identifying biomarkers that differentiate latent and active TB disease enables effective TB control, as early detection, treatment of active TB and preventive treatment of individuals with LTBI are crucial steps involved in TB control. Here, we have evaluated the frequency of antigen-specific memory and regulatory T (Treg) cells in 15 healthy household contacts (HHC) and 15 pulmonary TB patients (PTB) to identify biomarkers for differential diagnosis of LTBI and active TB. Among all the antigens tested in the present study, early secretory antigenic target-6 (ESAT-6) -specific CD4⁺ and CD8⁺ central memory (Tcm) cells showed 93% positivity in HHC and 20% positivity in PTB. The novel test antigens Rv0753c and Rv0009 both displayed 80% and 20% positivity in HHC and PTB, respectively. In contrast to Tcm cells, effector memory T (Tem) cells showed a higher response in PTB than HHC; both ESAT-6 and Rv0009 showed similar positivity of 80% in PTB and 33% in HHC. PTB patients have a higher proportion of circulating antigen-reactive Treg cells (CD4⁺  CD25⁺  FoxP3⁺ ) than LTBI. Rv2204c-specific Treg cells showed maximum positivity of 73% in PTB and 20% in HHC. Collectively, our data conclude that ESAT-6-specific Tcm cells and Rv2204c-specific Treg cells might be useful biomarkers to discriminate LTBI from active TB.

Chinese medicine Ginseng and Astragalus granules ameliorate autoimmune diabetes by upregulating both CD4+FoxP3+ and CD8+CD122+PD1+ regulatory T cells

Type 1 diabetes mellitus (T1DM) is an autoimmune disease mainly mediated by effector T cells that are activated by autoantigen, thereby resulting in the destruction of pancreatic islets and deficiency of insulin. Cyclosporine is widely used as an immunosuppressant that suppresses autoimmunity in clinic. However, continuous treatments with conventional immunosuppressive drugs may cause severe side effects. Therefore it is important to seek alternative medicine. Chinese medicine Ginseng and Astragalus granule (GAG) was used to successfully treat type 2 diabetes mellitus in clinic in China. Here we found that GAG ameliorated T1DM in autoimmune NOD mice by increasing the level of insulin and reducing the level of blood glucose. Treatments with both GAG and CsA further decreased the blood glucose level. Moreover, GAG increased both CD4+FoxP3+ and CD8+CD122+PD-1+ Treg numbers in both spleens and lymph nodes of NOD mice. In particular, GAG could reverse a decline in CD4+FoxP3+ Tregs resulted from CsA treatments. The percentage of effector/memory CD8+ T cells (CD44^highCD62L^low) was significantly reduced by GAG, especially in the presence of low-doses of CsA. Histopathology also showed that GAG attenuated cellular infiltration and lowered CD3+ T cell numbers around and in islets. Thus, we demonstrated that GAG ameliorated autoimmune T1DM by upregulating both CD4+FoxP3+ and CD8+CD122+PD-1+ Tregs while GAG synergized with CsA to further suppress autoimmunity and T1DM by reversing the decline in CD4+FoxP3+ Tregs resulted from CsA treatments. This study may have important clinical implications for the treatment of T1DM using traditional Chinese medicine.

Phenotypic characterization of regulatory T cells from antiretroviral-naive HIV-1-infected people

Regulatory T (Treg) cells play a key role in dampening excessive immune activation. However, antiretroviral therapy (ART) -naive HIV-1 infection maintains the immune system in a sustained state of activation that could alter both Treg cell surface markers and functions. As Treg cell surface markers are directly linked to their functions the overall objective of this study was to determine how ART-naive HIV infection affects the phenotypic properties of Treg cells. Our data showed that in ART-naive HIV-1 infection, Treg cells are dominated by effector (CD45RA⁺  CD27^-  CCR7^- CD62L^- ) and effector memory (CD45RA^-  CD27^-  CCR7^-  CD62L^- ) cells. In contrast Treg cells from HIV-negative individuals were mainly naive (CD45RA⁺  CD27⁺  CCR7⁺  CD62L⁺ ) and central memory (CD45RA^- CD27⁺  CCR7⁺  CD62L⁺ ) cells. Whereas effector and effector memory Treg cells showed enhanced expression of CD39 (P < 0·05), CD73 (P < 0·001), HLA-DR and CD38 (P < 0·001); naive and central memory Treg cells showed a significant reduction in the expression of these markers. Overall Treg cell frequencies within total CD4⁺ T cells correlated positively with plasmatic HIV-1 viral load. As increased viral load is associated with augmented CD4⁺ T-cell destruction; this could suggest a resistance of peripheral Treg cells to HIV-1 destruction. Hence the modulation of Treg cell phenotype and frequencies could be considered in designing immunotherapeutic strategies targeting immune system restoration during HIV-1 infection.

Ulinastatin ameliorates tissue damage of severe acute pancreatitis through modulating regulatory T cells

BACKGROUND

Ulinastatin or urinary trypsin inhibitor (UTI) has been shown to ameliorate the inflammatory response induced by experimental severe acute pancreatitis (SAP) and hence reduce the mortality, however the mechanism of its action remains incompletely understood. We have investigated the effect of ulinastatin on regulatory T-cells (Tregs) in an established rat model of SAP.

METHODS

We established a rat SAP model by injecting 5% Na-taurocholate into the pancreatic duct and treated the SAP rats with ulinastatin with different dose level (5000, 10000, 30000 U/kg) through intraperitoneal injection at 0, 6 and 12 h.

RESULTS

We showed that the tissue damage of pancreas and the mortality of the SAP rats were significantly reduced by ulinastatin. We also showed that in the SAP rats the frequencies of CD4+ T cells and Tregs, as well as the expressions of TGF-β1, CTLA-4, and Foxp3 were decreased in the SAP animals while IL-1β, IL-10 and TNF-α were significantly increased. Treatment with ulinastatin up-regulated the proportion of Tregs in CD4+ T cells and the expression of IL-10, Foxp3 and CTLA-4 in the SAP rats in a dose dependence fashion, while down-regulating the levels of L-1β and TNF-α, myeloperoxidase (MPO) activity.

CONCLUSIONS

Our findings suggest that ulinastatin alleviates inflammatory response and tissue damage in SAP rats by increasing the proportion of Tregs. Our study provides a new mechanism for the beneficial effect of ulinastatin in SAP rat model.

Skewing toward Treg and Th2 responses is a characteristic feature of sustained remission in ANCA-positive granulomatosis with polyangiitis

The objective of our study was to evaluate the T-helper (Th) and regulatory T (Treg) cell profile in ANCA-positive granulomatosis with polyangiitis (GPA) and its relation to disease activity. In a prospective study, we studied two groups of GPA patients: (i) disease flare (active-GPA, BVAS>6, n = 19), (ii) sustained remission (≥ 1-year prior enrollment, inactive-GPA, BVAS = 0, n = 18). 24 age-sex matched healthy subjects served as controls. Active-GPA patients were followed for 6 months and reevaluated during remission (early remission; n = 13). We analyzed subsets of Th-cells (flow cytometry), production of signature cytokines by in vitro stimulated lymphocytes, and broad spectrum of serum cytokines (Luminex). In all GPA patients we observed expansion of effector Th17 cells, and increased production of IL-17A by in vitro stimulated T cells, as compared to controls. Disease flare was characterized by marked reduction in Treg cells, whereas in sustained remission we showed expansion of both Treg and Th2 subset. Finally, analyzing the cytokine profile, we identified CCL23 and LIGHT, as potential biomarkers of active disease. We conclude that in GPA, expansion of Treg and Th2 lymphocytes in parallel to increased Th17 response is a characteristic feature of sustained remission. In contrast, Treg cells are markedly decreased in disease flare.

Impaired Function of Peripherally Induced Regulatory T Cells in Hosts at High Risk of Graft Rejection

Regulatory T cells (Tregs) are crucial for allograft survival. Tregs can be divided into thymus-derived natural Tregs (tTregs) and peripherally-derived induced Tregs (pTregs). Here, we determine whether the suppressive function of Treg subsets is hampered in hosts who are at high risk for rejecting their graft. To induce graft beds that promote high risk of transplant rejection, intrastromal corneal sutures were placed two weeks prior to the transplant procedure in mice. We demonstrate that in high-risk recipients the frequencies and function of pTregs (but not tTregs) are suppressed. Reduced function of pTregs correlated with decreased expression of CTLA-4, interleukin-10, and transforming growth factor-β. Adoptive transfer of pTregs from mice at low risk of subsequent graft rejection is able to rescue graft survival in recipients that are at high risk of rejecting their grafts. Our data suggest that impaired function of pTregs, but not tTregs, mediates the loss of immune tolerance and promotes allograft rejection.

Simian Immunodeficiency Virus-Producing Cells in Follicles Are Partially Suppressed by CD8+ Cells In Vivo

Human immunodeficiency virus (HIV)- and simian immunodeficiency virus (SIV)-specific CD8+ T cells are typically largely excluded from lymphoid B cell follicles, where HIV- and SIV-producing cells are most highly concentrated, indicating that B cell follicles are somewhat of an immunoprivileged site. To gain insights into virus-specific follicular CD8+ T cells, we determined the location and phenotype of follicular SIV-specific CD8+ T cells in situ, the local relationship of these cells to Foxp3+ cells, and the effects of CD8 depletion on levels of follicular SIV-producing cells in chronically SIV-infected rhesus macaques. We found that follicular SIV-specific CD8+ T cells were able to migrate throughout follicular areas, including germinal centers. Many expressed PD-1, indicating that they may have been exhausted. A small subset was in direct contact with and likely inhibited by Foxp3+ cells, and a few were themselves Foxp3+ In addition, subsets of follicular SIV-specific CD8+ T cells expressed low to medium levels of perforin, and subsets were activated and proliferating. Importantly, after CD8 depletion, the number of SIV-producing cells increased in B cell follicles and extrafollicular areas, suggesting that follicular and extrafollicular CD8+ T cells have a suppressive effect on SIV replication. Taken together, these results suggest that during chronic SIV infection, despite high levels of exhaustion and likely inhibition by Foxp3+ cells, a subset of follicular SIV-specific CD8+ T cells are functional and suppress viral replication in vivo These findings support HIV cure strategies that augment functional follicular virus-specific CD8+ T cells to enhance viral control.

IMPORTANCE

HIV- and SIV-specific CD8+ T cells are typically largely excluded from lymphoid B cell follicles, where virus-producing cells are most highly concentrated, suggesting that B cell follicles are somewhat of an immunoprivileged site where virus-specific CD8+ T cells are not able to clear all follicular HIV- and SIV-producing cells. To gain insights into follicular CD8+ T cell function, we characterized follicular virus-specific CD8+ T cells in situ by using an SIV-infected rhesus macaque model of HIV. We found that subsets of follicular SIV-specific CD8+ T cells are able to migrate throughout the follicle, are likely inhibited by Foxp3+ cells, and are likely exhausted but that, nonetheless, subsets are likely functional, as they express markers consistent with effector function and show signs of suppressing viral replication in vivo These findings support HIV cure strategies that increase the frequency of functional follicular virus-specific CD8+ T cells.

Oxidative Stress and Treg and Th17 Dysfunction in Systemic Lupus Erythematosus

Systemic lupus erythematosus (SLE) is an autoimmune disease that involves multiple organ systems. The pathogenic mechanisms that cause SLE remain unclear; however, it is well recognized that the immune balance is disturbed and that this imbalance contributes to the autoimmune symptoms of SLE. Oxidative stress represents an imbalance between the production and manifestation of reactive oxygen species and the ability of the biological system to readily detoxify the reactive intermediates or to repair the resulting damage. In humans, oxidative stress is involved in many diseases, including atherosclerosis, myocardial infarction, and autoimmune diseases. Numerous studies have confirmed that oxidative stress plays an important role in the pathogenesis of SLE. This review mainly focuses on the recent research advances with respect to oxidative stress and regulatory T (Treg)/helper T 17 (Th17) cell dysfunction in the pathogenesis of SLE.

Vogt-Koyanagi-Harada disease: Novel insights into pathophysiology, diagnosis and treatment

Vogt-Koyanagi-Harada (VKH) disease is one of the major vision-threatening diseases in certain populations, such as Asians, native Americans, Hispanics and Middle Easterners. It is characterized by bilateral uveitis that is frequently associated with neurological (meningeal), auditory, and integumentary manifestations. Although the etiology and pathogenesis of VKH disease need to be further elucidated, it is widely accepted that the clinical manifestations are caused by an autoimmune response directed against melanin associated antigens in the target organs, i.e. the eye, inner ear, meninges and skin. In the past decades, accumulating evidence has shown that genetic factors, including VKH disease specific risk factors (HLA-DR4) and general risk factors for immune mediated diseases (IL-23R), dysfunction of immune responses, including the innate and adaptive immune system and environmental triggering factors are all involved in the development of VKH disease. Clinically, the criteria of diagnosis for VKH disease have been further improved by the employment of novel imaging techniques for the eye. For the treatment, early and adequate corticosteroids are still the mainstream regime for the disease. However, immunosuppressive and biological agents have shown benefit for the treatment of VKH disease, especially for those patients not responding to corticosteroids. This review is focused on our current knowledge of VKH disease, especially for the diagnosis, pathogenesis (genetic factors and immune mechanisms), ancillary tests and treatment. A better understanding of the role of microbiome composition, genetic basis and ongoing immune processes along with the development of novel biomarkers and objective quantitative assays to monitor intraocular inflammation are needed to improve current management of VKH patients.

Relationship between regulatory T cells subsets and lipid profile in dyslipidemic patients: a longitudinal study during atorvastatin treatment

Background

The CD4+ T-lymphocytes and their subtype CD4 + CD25^highFoxP3+ regulatory T cells are receiving growing interest as major regulators of atherogenesis. We sought to investigate 1) whether the CD4 + cell subsets were expressed differently in dyslipidemic patients (Pts) and healthy subjects (HS) and 2) whether atorvastatin treatment could be associated in-vivo and in-vitro with cell changes in expression and functional response.

Methods

CD4+ subsets frequency (CD4 + CD25^highFoxP3+, CD4 + CD25-FoxP3+) and mRNA expression for FoxP3, IL-10 and TGF-β were evaluated in 30 consecutive Pts at baseline and after a 3-month atorvastatin therapy, and in 17 HS.

Results

The % of CD4 + cells did not differ between HS and Pts. The % of CD4 + CD25^highFoxP3+ was higher in Pts than HS and did not change during treatment. The CD4 + CD25-FoxP3+ cells were similar between the two groups and were lower in Pts at visit 2. Cytokine expression and FoxP3 did not differ in HS and Pts and no substantial change was observed during treatment. At visit 1, CD4 + CD25^highFoxP3+ cells were significantly correlated with both total-cholesterol (r = 0.570, P = 0.0002), LDL-cholesterol (r = 0.715, P = 0.0001), Apolipoprotein B (r = 0.590, P = 0.0001). In-vitro atorvastatin (up to 5 μM) failed to induce any significant modulation of cell functions.

Conclusion

CD4 + CD25^highFoxP3+ regulatory cells seem to be over-stimulated in the early pre-clinical phase of atherosclerosis and a relationship exists between their frequency and circulating lipids. A potential immuno-modulation by statin treatment is not achieved through a normalization in peripheral CD4 + cell subsets.

Paeoniflorin regulates the function of human peripheral blood mononuclear cells stimulated by rhIL-1β by up-regulating Treg expression

The aim of the present study was to investigate the effect of paeoniflorin (Pae) on recombinant human interleukin-1β (rhIL-1β)-stimulated human peripheral blood mononuclear cells (PBMCs) in vitro. PBMCs were collected by Ficoll density gradient centrifugation and were co-cultured with rhIL-1β for different time periods. The proliferation response was determined by a cell counting kit-8 (CCK-8) assay. The production of IL-17 and IL-10 was measured by enzyme-linked immunosorbent assay (ELISA). The percentage of CD4(+)CD25(+)Foxp3(+) regulatory T cells (Treg) was detected by flow cytometry analysis. These results indicated that rhIL-1β stimulation induced the proliferation of PBMCs in a concentration- and time-dependent manner; it also increased the level of IL-17 and decreased the level of IL-10 in a concentration-dependent manner. The flow cytometry analysis demonstrated that the stimulation of rhIL-1β significantly downregulated the percentage of CD4(+)CD25(+)Foxp3(+) Treg in CD4(+) T cells. However, administration of Pae significantly suppressed the proliferation response of rhIL-1β-induced PBMCs and regulated the secretion function of IL-17 and IL-10. Additional experiments demonstrated that Pae treatment significantly reduced rhIL-1β-induced decreases in PBMCs CD4(+)CD25(+)Foxp3(+) subpopulation numbers. These results suggest that the anti-inflammatory action of Pae is attributable to its regulation of IL-17/IL-10 secretion and Treg expression.

Regulatory T cells: Mechanisms of suppression and impairment in autoimmune liver disease

There are three classic liver diseases with probable autoimmune etiology: primary biliary cirrhosis, primary sclerosing cholangitis, and autoimmune hepatitis. The occurrence of these autoimmune conditions is determined by the breakdown of immune-regulatory mechanisms that in health are responsible for maintaining immunological tolerance against self-antigens. Among the multiple T cell subsets with suppressive function, the regulatory T cells (Tregs), defined by the expression of CD4, the IL-2 receptor α chain (CD25), and the transcription factor FOXP3, have emerged as having a central role in maintaining immune-tolerance to autoantigens. Tregs are equipped with an array of mechanisms of suppression, including the modulation of antigen presenting cell maturation and function, the killing of target cells, the disruption of metabolic pathways, and the production of anti-inflammatory cytokines. In all the three autoimmune liver diseases mentioned above, there is evidence pointing for either a reduced frequency and/or function of Tregs. Here, we review the definition, phenotypic characteristics, and mechanisms of suppression employed by Tregs and then we discuss the evidence available pointing to their impairment in patients with autoimmune liver disease.

Rituximab-induced interleukin-15 reduction associated with clinical improvement in rheumatoid arthritis

Rituximab therapy alters all aspects of B-cell participation in the disturbed immune response of rheumatoid arthritis patients. To determine the impact of B-cell depletion on other immune compartments, we analysed levels of soluble and surface interleukin-15 (IL-15) along with the frequency of IL-15-related subsets after rituximab treatment. We then studied the correlation of observed changes with clinical activity. Heparinized blood samples from 33 rheumatoid arthritis patients were collected on days 0, 30, 90 and 180 after each of three rituximab cycles. Serum cytokine levels were determined by ELISA. Interleukin-15 trans-presentation was analysed by cytometry. Flow cytometry with monoclonal antibodies was performed to analyse circulating cell subsets. Interleukin-15 was detected in the serum of 25 patients before initiating the treatment. Rituximab then progressively reduced serum IL-15 (138 ± 21 pg/ml at baseline, 48 ± 18 pg/ml after third cycle, P = 0·03) along with IL-17 (1197 ± 203 pg/ml at baseline, 623 ± 213 pg/ml after third cycle, P = 0·03) and tended to increase the frequency of circulating regulatory T cells (3·1 ± 1 cells/μl at baseline, 7·7 ± 2 cells/μl after third cycle). Rituximab also significantly decreased IL-15 trans-presentation on surface monocytes of patients negative for IL-15 serum (mean fluorescence intensity: 4·82 ± 1·30 at baseline, 1·42 ± 0·69 after third cycle P = 0·05). Reduction of serum IL-15 was associated with decrease in CD8(+)  CD45RO(+) /RA(+) ratio (1·17 ± 0·21 at baseline, 0·36 ± 0·06 at third cycle, P = 0·02). DAS28, erythrocyte sedimentation rate and C-reactive protein correlated significantly with CD8(+)  CD45RO(+) /RA(+) ratio (R = 0·323, R = 0·357, R = 0·369 respectively, P < 0·001). Our results suggest that sustained clinical improvement after rituximab treatment is associated with IL-15/memory T-cell-related mechanisms beyond circulating B cells.

Id1 expression promotes T regulatory cell differentiation by facilitating TCR costimulation

T regulatory (Treg) cells play crucial roles in the regulation of cellular immunity. The development of Treg cells depends on signals from TCRs and IL-2Rs and is influenced by a variety of transcription factors. The basic helix-loop-helix proteins are known to influence TCR signaling thresholds. Whether this property impacts Treg differentiation is not understood. In this study, we interrogated the role of basic helix-loop-helix proteins in the production of Treg cells using the CD4 promoter-driven Id1 transgene. We found that Treg cells continued to accumulate as Id1 transgenic mice aged, resulting in a significant increase in Treg cell counts in the thymus as well as in the periphery compared with wild-type controls. Data from mixed bone marrow assays suggest that Id1 acts intrinsically on developing Treg cells. We made a connection between Id1 expression and CD28 costimulatory signaling because Id1 transgene expression facilitated the formation of Treg precursors in CD28(-/-) mice and the in vitro differentiation of Treg cells on thymic dendritic cells despite the blockade of costimulation by anti-CD80/CD86. Id1 expression also allowed in vitro Treg differentiation without anti-CD28 costimulation, which was at least in part due to enhanced production of IL-2. Notably, with full strength of costimulatory signals, however, Id1 expression caused modest but significant suppression of Treg induction. Finally, we demonstrate that Id1 transgenic mice were less susceptible to the induction of experimental autoimmune encephalomyelitis, thus illustrating the impact of Id1-mediated augmentation of Treg cell levels on cellular immunity.

CD4(+) CD25(high) forkhead box protein 3(+) regulatory T lymphocytes suppress interferon-γ and CD107 expression in CD4(+) and CD8(+) T cells from tuberculous pleural effusions

Tuberculous pleural effusion is characterized by a T helper type 1 (Th1) profile, but an excessive Th1 response may also cause tissue damage that might be controlled by regulatory mechanisms. In the current study we investigated the role of regulatory T cells (Treg ) in the modulation of Th1 responses in patients with tuberculous (TB) pleurisy. Using flow cytometry we evaluated the proportion of Treg (CD4(+) CD25(high) forkhead box protein 3(+) ), interferon (IFN)-γ and interleukin (IL)-10 expression and CD107 degranulation in peripheral blood (PB) and pleural fluid (PF) from patients with TB pleurisy. We demonstrated that the proportion of CD4(+) CD25(+) , CD4(+) CD25(high) FoxP3(+) and CD8(+) CD25(+) cells were increased in PF compared to PB samples. Mycobacterium tuberculosis stimulation increased the proportion of CD4(+) CD25(low/neg) IL-10(+) in PB and CD4(+) CD25(low/neg) IFN-γ(+) in PF; meanwhile, CD25(high) mainly expressed IL-10 in both compartments. A high proportion of CD4(+) CD107(+) and CD8(+) CD107(+) cells was observed in PF. Treg depletion enhanced the in-vitro M. tuberculosis-induced IFN-γ and CD4(+) and CD8(+) degranulation responses and decreased CD4(+) IL-10(+) cells in PF. Our results demonstrated that in TB pleurisy Treg cells effectively inhibit not only IFN-γ expression but also the ability of CD4(+) and CD8(+) cells to degranulate in response to M. tuberculosis.

Critical stoichiometric ratio of CD4(+) CD25(+) FoxP3(+) regulatory T cells and CD4(+) CD25(-) responder T cells influence immunosuppression in patients with B-cell acute lymphoblastic leukaemia

Regulatory T (Treg) cells act to suppress activation of the immune system and thereby maintain immunological homeostasis and tolerance to self-antigens. The frequency and suppressing activity of Treg cells in general are high in different malignancies. We wanted to identify the role and regulation of CD4(+)  CD25(+)  FoxP3(+) Treg cells in B-cell acute lymphoblastic leukaemia (B-ALL). We have included patients at diagnosis (n = 54), patients in clinical remission (n = 32) and normal healthy individuals (n = 35). These diagnosed patients demonstrated a lower number of CD4(+)  CD25(+) cells co-expressing a higher level of FoxP3, interleukin-10, transforming growth factor-β and CD152/CTLA-4 than the normal population. Treg cells from patients showed a higher suppressive capability on CD4(+)  CD25(-) responder T (Tresp) cells than normal. The frequency and immunosuppressive potential of CD4(+)  CD25(+)  FoxP3(+) Treg cells became high with the progression of malignancy in B-ALL. Relative distribution of Tresp and Treg cells was only ~5 : 1 in B-ALL but ~35 : 1 in normal healthy individuals, further confirming the elevated immunosuppression in patients. A co-culture study at these definite ex vivo ratios, indicated that Treg cells from B-ALL patients exhibited higher immunosuppression than Treg cells from normal healthy individuals. After chemotherapy using the MCP841 protocol, the frequency of CD4(+)  CD25(+) cells was gradually enhanced with the reduction of FoxP3, interleukin-10 positivity corresponded with disease presentation, indicating reduced immunosuppression. Taken together, our study indicated that the CD4(+)  CD25(+)  FoxP3(+) Treg cells played an important role in immunosuppression, resulting in a positive disease-correlation in these patients. To the best of our knowledge, this is the first detailed report on the frequency, regulation and functionality of Treg cells in B-ALL.

Allergen immunotherapy and tolerance

Successful allergen-specific immunotherapy (AIT) is associated with a marked decrease in symptoms on allergen exposure, a reduced requirement for 'rescue' anti-allergic drugs and improvement in patients' quality of life. These benefits persist for at least several years following discontinuation of immunotherapy - the hallmark of clinical and immunological tolerance. AIT has been shown to modulate both innate and adaptive immunological responses. Early suppression of innate effector cells of allergic inflammation (mast cells, basophils), regulation of pro-allergic T helper 2 type (Th 2) responses and IgE+ B cell responses have been shown to occur both in the tissue and in the peripheral blood during AIT. The allergen-tolerant state is associated with local and systemic induction of distinct populations of allergen-specific T regulatory cells including IL-10+ Tregs (Tr1 cells), TGF-β+ Tregs and FoxP3+ memory T regs. B cells are switched in favour of producing IgG (particularly IgG4) antibodies and associated blocking activity for IgE-dependent events, including basophil activation and IgE-facilitated allergen binding to B cells. An induction of IL-10+ B regulatory cells and alterations in dendritic cell subsets have also recently been described. These events are followed by the induction of T regulatory cells, suppression of allergen-specific T cell proliferation and immune deviation from Th2 in favour of Th1 responses. Alternative mechanisms of tolerance include apoptosis/deletion of antigen-specific memory Th2 cells and/or a failure of co-stimulation leading to T cell anergy.

Allospecific CD8 T suppressor cells induced by multiple MLC stimulation or priming in the presence of ILT3.Fc have similar gene expression profiles

Alloantigen specific CD8 T suppressor cells can be generated in vitro either by multiple stimulations of CD3 T cells with allogeneic APC or by single stimulation in primary MLC containing recombinant ILT3.Fc protein. The aim of the present study was to determine whether multiple MLC stimulation induced in CD8(+) CD28(-) T suppressor cells molecular changes that are similar to those observed in CD8 T suppressor cells from primary MLC containing ILT3.Fc protein. Our study demonstrates that the characteristic signatures of CD8 T suppressor cells, generated by either of these methods are the same consisting of up-regulation of the BCL6 transcriptional repressor and down-regulation of inflammatory microRNAs, miR-21, miR-30b, miR-146a, and miR-155 expression. In conclusion microRNAs which are increased under inflammatory conditions in activated CD4 and CD8 T cells with helper or cytotoxic function show low levels of expression in CD8 T cells which have acquired antigen-specific suppressor activity.

APL-1, an altered peptide ligand derived from human heat-shock protein 60, selectively induces apoptosis in activated CD4+ CD25+ T cells from peripheral blood of rheumatoid arthritis patients

Rheumatoid arthritis (RA) is a chronic T-cell mediated autoimmune disease that affects primarily the joints. The induction of immune tolerance through antigen-specific therapies for the blockade of pathogenic CD4+ T cells constitutes a current focus of research. In this focus it is attempted to simultaneously activate multiple regulatory mechanisms, such as: apoptosis and regulatory T cells (Tregs). APL-1 is an altered peptide ligand derived from a novel CD4+ T-cell epitope of human heat-shock protein of 60kDa, an autoantigen involved in the pathogenesis of RA. Previously, we have reported that APL-1 induces CD4+ CD25(high)Foxp3+ Tregs in several systems. Here, we investigated the ability of APL-1 in inducing apoptosis in PBMCs from RA patients, who were classified as active or inactive according to their DAS28 score. APL-1 decreased the viability of PBMCs from active but not from inactive patients. DNA fragmentation assays and typical morphological features clearly demonstrated that APL-1 induced apoptosis in these cells. Activated CD4+ CD25+ T cells but not resting CD4+ CD25- T cells were identified as targets of APL-1. Furthermore, CD4+ T-cell responses to APL-1 were found to be dependent on antigen presentation via the HLA-DR molecule. Thus, APL-1 is a regulatory CD4+ T cell epitope which might modulate inflammatory immune responses in PBMCs from RA patients by inducing CD4+ CD25(high)Foxp3+ Tregs and apoptosis in activated CD4+ T cells. These results support further investigation of this candidate drug for the treatment of RA.

Rapamycin induces ILT3(high)ILT4(high) dendritic cells promoting a new immunoregulatory pathway

ILT3(high)ILT4(high) dendritic cells (DCs) may cause anergy in CD4(+)CD45RO(+)CD25(+) T cells transforming them into regulatory T cells (Tregs). Here, we tested whether chronic exposure to rapamycin may modulate this immunoregulatory pathway in renal transplant recipients. Forty renal transplant patients with biopsy-proven chronic allograft nephropathy and receiving calcineurin inhibitors were randomly assigned to either calcineurin inhibitor dose reduction or withdrawal with rapamycin introduction. At conversion and 2 years thereafter, we measured the rapamycin effects on circulating DCs (BDCA1/BDCA2 and ILT3/ILT4 expression), CD4(+)/CD25(high)/Foxp3(+) Tregs, CD8(+)/CD28(-) T cells, and the Th1/Th2 balance in graft biopsies. In rapamycin-treated patients, peripheral BDCA2(+) cells were significantly increased along with ILT3/ILT4(+) DCs. The number of circulating CD4(+)/CD25(high)/Foxp3(+)/CTLA4(+) Tregs, CD8(+)CD28(-) T cells, and HLA-G serum levels were higher in the rapamycin-treated group. The number of ILT3/ILT4(+)BDCA2(+) DC was directly and significantly correlated with circulating Tregs and CD8(+)CD28(-) T cells. ILT3/ILT4 expression was increased in kidney biopsies at the end of the study period along with a significant bias toward a Th2 response within the graft only in the rapamycin-treated patients. Thus, rapamycin induces the upregulation of ILT3 and ILT4 on the DC surface, and this effect is associated with an increase in the number of Tregs and expansion of the CD8(+)CD28(-) T cell population. This suggests that mTOR inhibition may promote a novel immunoregulatory pathway.