IL-2 and IL-15 dependent thymic development of Foxp3-expressing regulatory T lymphocytes

Differentiation and regulation of CD4+ T cell subsets in Parkinson's disease

Parkinson's disease (PD) is the second most common neurodegenerative disease, and its hallmark pathological features are the loss of dopaminergic (DA) neurons in the midbrain substantia nigra pars compacta (SNpc) and the accumulation of alpha-synuclein (α-syn). It has been shown that the integrity of the blood-brain barrier (BBB) is damaged in PD patients, and a large number of infiltrating T cells and inflammatory cytokines have been detected in the cerebrospinal fluid (CSF) and brain parenchyma of PD patients and PD animal models, including significant change in the number and proportion of different CD4+ T cell subsets. This suggests that the neuroinflammatory response caused by CD4+ T cells is an important risk factor for the development of PD. Here, we systematically review the differentiation of CD4+ T cell subsets, and focus on describing the functions and mechanisms of different CD4+ T cell subsets and their secreted cytokines in PD. We also summarize the current immunotherapy targeting CD4+ T cells with a view to providing assistance in the diagnosis and treatment of PD.

Lymphotoxin limits Foxp3+ regulatory T cell development from Foxp3lo precursors via IL-4 signaling

Regulatory T cells (Treg) are critical players of immune tolerance that develop in the thymus via two distinct developmental pathways involving CD25+Foxp3- and CD25-Foxp3lo precursors. However, the mechanisms regulating the recently identified Foxp3lo precursor pathway remain unclear. Here, we find that the membrane-bound lymphotoxin α1β2 (LTα1β2) heterocomplex is upregulated during Treg development upon TCR/CD28 and IL-2 stimulation. We show that Lta expression limits the maturational development of Treg from Foxp3lo precursors by regulating their proliferation, survival, and metabolic profile. Transgenic reporter mice and transcriptomic analyses further reveal that medullary thymic epithelial cells (mTEC) constitute an unexpected source of IL-4. We demonstrate that LTα1β2-lymphotoxin β receptor-mediated interactions with mTEC limit Treg development by down-regulating IL-4 expression in mTEC. Collectively, our findings identify the lymphotoxin axis as the first inhibitory checkpoint of thymic Treg development that fine-tunes the Foxp3lo Treg precursor pathway by limiting IL-4 availability.

Role of Treg cell subsets in cardiovascular disease pathogenesis and potential therapeutic targets

In the genesis and progression of cardiovascular diseases involving both innate and adaptive immune responses, inflammation plays a pivotal and dual role. Studies in experimental animals indicate that certain immune responses are protective, while others exacerbate the disease. T-helper (Th) 1 cell immune responses are recognized as key drivers of inflammatory progression in cardiovascular diseases. Consequently, the CD4+CD25+FOXP3+ regulatory T cells (Tregs) are gaining increasing attention for their roles in inflammation and immune regulation. Given the critical role of Tregs in maintaining immune-inflammatory balance and homeostasis, abnormalities in their generation or function might lead to aberrant immune responses, thereby initiating pathological changes. Numerous preclinical studies and clinical trials have unveiled the central role of Tregs in cardiovascular diseases, such as atherosclerosis. Here, we review the roles and mechanisms of Treg subsets in cardiovascular conditions like atherosclerosis, hypertension, myocardial infarction and remodeling, myocarditis, dilated cardiomyopathy, and heart failure. While the precise molecular mechanisms of Tregs in cardiac protection remain elusive, therapeutic strategies targeting Tregs present a promising new direction for the prevention and treatment of cardiovascular diseases.

Regulatory T Cells in Ovarian Carcinogenesis and Future Therapeutic Opportunities

Regulatory T cells (Tregs) have been shown to play a role in the development of solid tumors. A better understanding of the biology of Tregs, immune suppression by Tregs, and how cancer developed with the activity of Tregs has facilitated the development of strategies used to improve immune-based therapy. In ovarian cancer, Tregs have been shown to promote cancer development and resistance at different cancer stages. Understanding the various Treg-mediated immune escape mechanisms provides opportunities to establish specific, efficient, long-lasting anti-tumor immunity. Here, we review the evidence of Treg involvement in various stages of ovarian cancer. We further provide an overview of the current and prospective therapeutic approaches that arise from the modulation of Treg-related tumor immunity at those specific stages. Finally, we propose combination strategies of Treg-related therapies with other anti-tumor therapies to improve clinical efficacy and overcome tumor resistance in ovarian cancer.

IL-2 and IL-15 drive intrathymic development of distinct periphery-seeding CD4+Foxp3+ regulatory T lymphocytes

Development of Foxp3-expressing regulatory T-lymphocytes (Treg) in the thymus is controlled by signals delivered in T-cell precursors via the TCR, co-stimulatory receptors, and cytokine receptors. In absence of IL-2, IL-15 or their receptors, fewer Treg apparently develop in the thymus. However, it was recently shown that a substantial part of thymic Treg are cells that had recirculated from the periphery back to the thymus, troubling interpretation of these results. We therefore reassessed the involvement of IL-2 and IL-15 in the development of Treg, taking into account Treg-recirculation. At the age of three weeks, when in wt and IL-15-deficient (but not in IL-2-deficient) mice substantial amounts of recirculating Treg are present in the thymus, we found similarly reduced proportions of newly developed Treg in absence of IL-2 or IL-15, and in absence of both cytokines even less Treg developed. In neonates, when practically no recirculating Treg were found in the thymus, the absence of IL-2 led to substantially more reduced Treg-development than deficiency in IL-15. IL-2 but not IL-15 modulated the CD25, GITR, OX40, and CD73-phenotypes of the thymus-egress-competent and periphery-seeding Treg-population. Interestingly, IL-2 and IL-15 also modulated the TCR-repertoire expressed by developing Treg. Upon transfer into Treg-less Foxp3^sf mice, newly developed Treg from IL-2- (and to a much lesser extent IL-15-) deficient mice suppressed immunopathology less efficiently than wt Treg. Taken together, our results firmly establish important non-redundant quantitative and qualitative roles for IL-2 and, to a lesser extent, IL-15 in intrathymic Treg-development.

Boosting regulatory T cell function for the treatment of autoimmune diseases – That’s only half the battle!

Regulatory T cells (Treg) represent a subset of specialized T cells that are essential for the regulation of immune responses and maintenance of peripheral tolerance. Once activated, Treg exert powerful immunosuppressive properties, for example by inhibiting T cell-mediated immune responses against self-antigens, thereby protecting our body from autoimmunity. Autoimmune diseases such as multiple sclerosis, rheumatoid arthritis or systemic lupus erythematosus, exhibit an immunological imbalance mainly characterized by a reduced frequency and impaired function of Treg. In addition, there has been increasing evidence that – besides Treg dysfunction – immunoregulatory mechanisms fail to control autoreactive T cells due to a reduced responsiveness of T effector cells (Teff) for the suppressive properties of Treg, a process termed Treg resistance. In order to efficiently treat autoimmune diseases and thus fully induce immunological tolerance, a combined therapy aimed at both enhancing Treg function and restoring Teff responsiveness could most likely be beneficial. This review provides an overview of immunomodulating drugs that are currently used to treat various autoimmune diseases in the clinic and have been shown to increase Treg frequency as well as Teff sensitivity to Treg-mediated suppression. Furthermore, we discuss strategies on how to boost Treg activity and function, and their potential use in the treatment of autoimmunity. Finally, we present a humanized mouse model for the preclinical testing of Treg-activating substances in vivo.

Your Regulatory T Cells Are What You Eat: How Diet and Gut Microbiota Affect Regulatory T Cell Development

Modern industrial practices have transformed the human diet over the last century, increasing the consumption of processed foods. Dietary imbalance of macro- and micro-nutrients and excessive caloric intake represent significant risk factors for various inflammatory disorders. Increased ingestion of food additives, residual contaminants from agricultural practices, food processing, and packaging can also contribute deleteriously to disease development. One common hallmark of inflammatory disorders, such as autoimmunity and allergies, is the defect in anti-inflammatory regulatory T cell (Treg) development and/or function. Treg represent a highly heterogeneous population of immunosuppressive immune cells contributing to peripheral tolerance. Tregs either develop in the thymus from autoreactive thymocytes, or in the periphery, from naïve CD4⁺ T cells, in response to environmental antigens and cues. Accumulating evidence demonstrates that various dietary factors can directly regulate Treg development. These dietary factors can also indirectly modulate Treg differentiation by altering the gut microbiota composition and thus the production of bacterial metabolites. This review provides an overview of Treg ontogeny, both thymic and peripherally differentiated, and highlights how diet and gut microbiota can regulate Treg development and function.

Activation of the STAT5 Signaling Pathway by Yiqi Jiedu Formula Induces Regulatory T Cell-Mediated Alleviation of Corneal Immunopathological Damage in Mice With Recurrent Herpes Simplex Keratitis

This study aimed to investigate the effect of Yiqi Jiedu (YQJD) formula on the repair of corneal lesions in mice with recurrent herpes simplex virus keratitis (HSK). Sixty female BALB/c mice were randomly divided into three groups: a normal control group (Naive), a recurrence model group (Re), and a YQJD group. After inducing recurrence by ultraviolet irradiation, the ocular surfaces of different groups of mice were observed using a slit lamp and photographed, and ocular surface scores were calculated. The abundance of CD4⁺CD25⁺Foxp3⁺ regulatory T (Treg) cells was determined by flow cytometry in peripheral blood and spleen cells. The CD4⁺Foxp3⁺ Tregs were assessed by immunofluorescence in the cornea. The levels of the cytokines IL-10 and TGF-β in serum and splenocyte culture supernatants were detected by enzyme-linked immunosorbent assay. Furthermore, the activation status of the STAT5 signaling pathway was examined by protein blotting, and the effect of YQJD on Treg cells through inhibition of the STAT5 pathway was observed in vitro. YQJD alleviated corneal inflammation by enhancing the STAT5 signaling pathway, thereby promoting the differentiation of CD4⁺CD25⁺Foxp3⁺ Treg cells, increasing the levels of anti-inflammatory cytokines such as IL-10 and TGF-β, and maintaining immune tolerance. YQJD increased the proportion of CD4⁺Foxp3⁺ Treg cells; also, in the cornea, YQJD inhibited the aggregation of macrophages and CD4⁺ cells and reduced the proportion of Th17 cells and other pro-inflammatory cells. Moreover, YQJD promoted the secretion of IL-4 to protect the cornea, leading to the mitigation of corneal immunopathological damage. YQJD reduced corneal lesions in recurrent HSK mice by stimulating Treg cells, inducing immune tolerance, and inhibiting corneal immunopathological responses via modulation of the STAT5 signaling pathway.

Long-Term Suppression of Circulating Proinflammatory Cytokines in Multiple Sclerosis Patients Following Autologous Haematopoietic Stem Cell Transplantation

Autologous haematopoietic stem cell transplantation (AHSCT) is a therapeutic option for haematological malignancies, such as non-Hodgkin’s lymphoma (NHL), and more recently, for autoimmune diseases, such as treatment-refractory multiple sclerosis (MS). The immunological mechanisms underlying remission in MS patients following AHSCT likely involve an anti-inflammatory shift in the milieu of circulating cytokines. We hypothesised that immunological tolerance in MS patients post-AHSCT is reflected by an increase in anti-inflammatory cytokines and a suppression of proinflammatory cytokines in the patient blood. We investigated this hypothesis using a multiplex-ELISA assay to compare the concentrations of secreted cytokine in the peripheral blood of MS patients and NHL patients undergoing AHSCT. In MS patients, we detected significant reductions in proinflammatory T helper (Th)17 cytokines interleukin (IL)-17, IL-23, IL-1β, and IL-21, and Th1 cytokines interferon (IFN)γ and IL-12p70 in MS patients from day 8 to 24 months post-AHSCT. These changes were not observed in the NHL patients despite similar pre-conditioning treatment for AHSCT. Some proinflammatory cytokines show similar trends in both cohorts, such as IL-8 and tumour necrosis factor (TNF)-α, indicating a probable treatment-related AHSCT response. Anti-inflammatory cytokines (IL-10, IL-4, and IL-2) were only transiently reduced post-AHSCT, with only IL-10 exhibiting a significant surge at day 14 post-AHSCT. MS patients that relapsed post-AHSCT exhibited significantly elevated levels of IL-17 at 12 months post-AHSCT, unlike non-relapse patients which displayed sustained suppression of Th17 cytokines at all post-AHSCT timepoints up to 24 months. These findings suggest that suppression of Th17 cytokines is essential for the induction of long-term remission in MS patients following AHSCT.

TGF-β1-overexpressing mesenchymal stem cells reciprocally regulate Th17/Treg cells by regulating the expression of IFN-γ

Transforming growth factor (TGF)-β1 and mesenchymal stromal cells (MSCs) are two effective immunosuppressive agents for organ transplantation technology. This study aims to explore the molecular mechanism of TGF-β1-overexpressed MSCs on T cell immunosuppression. To achieve that, BM-MSCs were isolated from canine bone marrow, and their osteogenic differentiation and surface markers were detected. The TGF-β1 gene was transferred into lentivirus and modified MSCs (TGF-β1/MSCs) by lentivirus transfection. Furthermore, TGF-β1/MSCs were co-cultured with T cells to investigate their effect on differentiation and immune regulation. Results showed that TGF-β1/MSCs significantly downregulated the proportion of CD4⁺ CD8⁺ T cells in lymphocytes and significantly upregulated the proportion of CD4⁺ CD25⁺ T cells. Moreover, TGF-β1/MSCs significantly upregulated the expression of IL-10 in CD4⁺ T cells and downregulated the expression of IL-17A, IL-21, and IL-22. Meanwhile, interferon-γ (IFN-γ) neutralizing antibody blocked the effects of TGF-β1/MSCs on the differentiation inhibition of Th17. Overall, our results confirm the strong immunosuppressive effect of TGF-β1/MSCs in vitro and demonstrate that IFN-γ mediates the immunosuppressive effect of TGF-β1/MSC.

Modeling the Dynamics of T-Cell Development in the Thymus

The thymus hosts the development of a specific type of adaptive immune cells called T cells. T cells orchestrate the adaptive immune response through recognition of antigen by the highly variable T-cell receptor (TCR). T-cell development is a tightly coordinated process comprising lineage commitment, somatic recombination of Tcr gene loci and selection for functional, but non-self-reactive TCRs, all interspersed with massive proliferation and cell death. Thus, the thymus produces a pool of T cells throughout life capable of responding to virtually any exogenous attack while preserving the body through self-tolerance. The thymus has been of considerable interest to both immunologists and theoretical biologists due to its multi-scale quantitative properties, bridging molecular binding, population dynamics and polyclonal repertoire specificity. Here, we review experimental strategies aimed at revealing quantitative and dynamic properties of T-cell development and how they have been implemented in mathematical modeling strategies that were reported to help understand the flexible dynamics of the highly dividing and dying thymic cell populations. Furthermore, we summarize the current challenges to estimating in vivo cellular dynamics and to reaching a next-generation multi-scale picture of T-cell development.

The Function and Role of the Th17/Treg Cell Balance in Inflammatory Bowel Disease

Inflammatory bowel disease (IBD) is a chronic, inflammatory, and autoimmune disorder. The pathogenesis of IBD is not yet clear. Studies have shown that the imbalance between T helper 17 (Th17) and regulatory T (Treg) cells, which differentiate from CD4⁺ T cells, contributes to IBD. Th17 cells promote tissue inflammation, and Treg cells suppress autoimmunity in IBD. Therefore, Th17/Treg cell balance is crucial. Some regulatory factors affecting the production and maintenance of these cells are also important for the proper regulation of the Th17/Treg balance; these factors include T cell receptor (TCR) signaling, costimulatory signals, cytokine signaling, bile acid metabolites, and the intestinal microbiota. This article focuses on our understanding of the function and role of the balance between Th17/Treg cells in IBD and these regulatory factors and their clinical significance in IBD.

Future prospects for CD8+ regulatory T cells in immune tolerance

CD8⁺ Tregs have been long described and significant progresses have been made about their phenotype, their functional mechanisms, and their suppressive ability compared to conventional CD4⁺ Tregs. They are now at the dawn of their clinical use. In this review, we will summarize their phenotypic characteristics, their mechanisms of action, the similarities, differences and synergies between CD8⁺ and CD4⁺ Tregs, and we will discuss the biology, development and induction of CD8⁺ Tregs, their manufacturing for clinical use, considering open questions/uncertainties and future technically accessible improvements notably through genetic modifications.

Immunoregulatory role of IL-2/STAT5/CD4+CD25+Foxp3 Treg pathway in the pathogenesis of chronic osteomyelitis

Background

This study aimed to investigate immunoregulatory role of IL-2/STAT5/CD4+CD25+Foxp3 Treg pathway in pathogenesis of chronic osteomyelitis (COM).

Methods

Sprague-Dawley (SD) rats were injected with Staphylococcus aureus to establish COM model. 4 weeks later, the lesioned bones were collected and subjected to HE staining for examination of inflammatory infiltration. Enzyme-linked immunosorbent assay (ELISA) was employed to detect IL-2 expression in peripheral blood; flow cytometry was performed to detect CD25+CD4+Foxp3 Treg cells in peripheral blood. The mRNA expression of Foxp3 and CTLA-4 was detected by RT-PCR and the protein expression of STAT5 and p-STAT5 was detected by Western Blotting in CD25+CD4+Foxp3 Treg cells.

Results

In COM group, the periosteal thickening was observed in femur, and there were a large number of inflammatory cells in medullary cavity, accompanied by bone destruction. At 1, 2 and 4 weeks, IL-2 expression significantly increased, the proportion of CD4+CD25+FoxP3 Treg cells in peripheral monocytes markedly increased, the mRNA expression of Foxp3 and CTLA-4 and p-STAT5 protein expression increased dramatically in Treg cells as compared to control group (P<0.001).

Conclusions

IL-2/STAT5/CD4+CD25+Foxp3 Treg pathway may be involved in the pathogenesis of COM, and excessive immunosuppression may lead to persistent infectious inflammation, which may become a key target for future treatment of COM.

PM2.5 affects establishment of immune tolerance in newborn mice by reducing PD-L1 expression

This study was conducted to determine whether exposure to particulate matter 2.5 (PM_2.5) affects the immune tolerance of neonatal mice via the regulation of PD-L1 expression. One-week-old BALB/c mice were exposed to PM_2.5 for 8 days. From day 8 to day 18, the mice were treated with 5 μg house dust mite (HDM) (i. n.) every two days. Adenovirus-carried PD-L1 overexpression vectors were infected into mice via nasal inhalation 6 days after exposure to PM_2.5. Airway hyperresponsiveness (AHR) was examined in mice 19 days after exposure to PM_2.5, and the related parameters of airway inflammation were studied on day 22. Co-exposure to PM_2.5 and HDM reduced PD-L1 expression but greatly increased infiltration of inflammatory cells, which was reversed by PD-L1 overexpression. Co-exposure to PM_2.5 and HDM also elevated serum IL-4, IL-5 and IL-13 levels and reduced TGF-β level. Exposure to PM_2.5 alone slightly increased the numbers of dendritic cells (DCs) but reduced the numbers of antigen-presenting cells expressing PD-L1 and Treg cells. Therefore, early exposure to PM_2.5 reduced PD-L1 expression in the lungs of neonatal mice, which interfered with immune tolerance establishment and subsequently resulted in allergic airway inflammation.

Effects of indoor coal fine particulate matter on the expression levels of inflammatory factors in ovalbumin-induced mice

Objective: Cooking and heating with coal is the main source of household air pollution in acid rain-plagued areas of China and is a leading contributor to disease burden. In this study, we investigated the adverse effects of exposure to indoor fine particulate matter emission from coal combustion on the expression levels of inflammatory factors in ovalbumin (OVA)-induced mice. Methods: Forty BALB/c male mice were randomly divided into four groups (control group, PM2.5 group, OVA group, and OVA + PM2.5 group; n = 10) and treated with ovalbumin (OVA) or PM2.5, alone or together. Interleukin-4 (IL-4), interleukin-7 (IL-7), interleukin-8 (IL-8), interleukin-17 (IL-17), transforming growth factor β1 (TGF-β1), and interferon γ (IFN-γ) protein expression levels were measured in bronchoalveolar lavage fluid (BALF). Additionally, serum immunoglobulin (Ig) IgE and IgG1 levels were measured. The mRNA expression levels of IL-7 and IFN-γ in pulmonary tissue were also analyzed. Bronchoalveolar lavage (BAL), inflammatory cell counts, and histopathological examinations were also performed. Results: Exposure to PM2.5 + OVA induced abnormal pathological changes and inflammatory responses in lungs compared to the control. The levels of IL-4, IL-7, IL-8 and IL-17 in BALF from the OVA + PM2.5 group were higher than those in BALF from the control group, OVA group, and PM2.5 group (P < 0.05). PM2.5 plus OVA significantly raised the serum IgE and IgG1 levels compared with the control group. An increasing IL-7 mRNA trend was found among the treatment groups (P < 0.05). The expression level of IFN-γ mRNA was significantly higher in the control group than in the other 3 groups (P < 0.05). Conclusion: Indoor coal PM2.5 was sufficient by itself to cause inflammatory cellular infiltration of pulmonary tissue, leading to organelle injury and physiological structure change. Additionally, it promoted the occurrence and development of asthma by influencing the expression levels of IL-7 and various relevant inflammatory factors (such as IL-4 and IL-8) and changing the equilibrium between Treg and Th17 cells.

Strain differences in thymic atrophy in rats immunized for EAE correlate with the clinical outcome of immunization

An accumulating body of evidence suggests that development of autoimmune pathologies leads to thymic dysfunction and changes in peripheral T-cell compartment, which, in turn, perpetuate their pathogenesis. To test this hypothesis, thymocyte differentiation/maturation in rats susceptible (Dark Agouti, DA) and relatively resistant (Albino Oxford, AO) to experimental autoimmune encephalomyelitis (EAE) induction was examined. Irrespective of strain, immunization for EAE (i) increased the circulating levels of IL-6, a cytokine causally linked with thymic atrophy, and (ii) led to thymic atrophy reflecting partly enhanced thymocyte apoptosis associated with downregulated thymic IL-7 expression. Additionally, immunization diminished the expression of Thy-1, a negative regulator of TCRαβ-mediated signaling and activation thresholds, on CD4+CD8+ TCRαβ^lo/hi thymocytes undergoing selection and thereby impaired thymocyte selection/survival. This diminished the generation of mature CD4+ and CD8+ single positive TCRαβ^hi thymocytes and, consequently, CD4+ and CD8+ recent thymic emigrants. In immunized rats, thymic differentiation of natural regulatory CD4+Foxp3+CD25+ T cells (nTregs) was particularly affected reflecting a diminished expression of IL-7, IL-2 and IL-15. The decline in the overall thymic T-cell output and nTreg generation was more pronounced in DA than AO rats. Additionally, differently from immunized AO rats, in DA ones the frequency of CD28- cells secreting cytolytic enzymes within peripheral blood CD4+ T lymphocytes increased, as a consequence of thymic atrophy-related replicative stress (mirrored in CD4+ cell memory pool expansion and p16^INK4a accumulation). The higher circulating level of TNF-α in DA compared with AO rats could also contribute to this difference. Consistently, higher frequency of cytolytic CD4+ granzyme B+ cells (associated with greater tissue damage) was found in spinal cord of immunized DA rats compared with their AO counterparts. In conclusion, the study indicated that strain differences in immunization-induced changes in thymopoiesis and peripheral CD4+CD28- T-cell generation could contribute to rat strain-specific clinical outcomes of immunization for EAE.