Regulation generation: the suppressive functions of human regulatory T cells

The yeast-human coevolution: Fungal transition from passengers, colonizers, and invaders

Fungi are the cause of more than a billion infections in humans every year, although their interactions with the host are still neglected compared to bacteria. Major systemic fungal infections are very unusual in the healthy population, due to the long history of coevolution with the human host. Humans are routinely exposed to environmental fungi and can host a commensal mycobiota, which is increasingly considered as a key player in health and disease. Here, we review the current knowledge on host-fungi coevolution and the factors that regulate their interaction. On one hand, fungi have learned to survive and inhabit the host organisms as a natural ecosystem, on the other hand, the host immune system finely tunes the response toward fungi. In turn, recognition of fungi as commensals or pathogens regulates the host immune balance in health and disease. In the human gut ecosystem, yeasts provide a fingerprint of the transient microbiota. Their status as passengers or colonizers is related to the integrity of the gut barrier and the risk of multiple disorders. Thus, the study of this less known component of the microbiota could unravel the rules of the transition from passengers to colonizers and invaders, as well as their dependence on the innate component of the host's immune response. This article is categorized under: Infectious Diseases > Environmental Factors Immune System Diseases > Environmental Factors Infectious Diseases > Molecular and Cellular Physiology.

Exercise preconditioning attenuates cerebral ischemia-induced neuronal apoptosis, Th17/Treg imbalance, and inflammation in rats by inhibiting the JAK2/STAT3 pathway

BACKGROUND

Exercise preconditioning (EP) is essential for preventing ischemic stroke. Recent studies have shown that EP exerts neuroprotective effects in the cerebral ischemia-reperfusion injury model. Nonetheless, there have been few reports on the relationship between EP and the Th17/Treg balance. Moreover, it is unclear whether the JAK2/STAT3 pathway is responsible for the neuroprotective effect of EP. Therefore, we aimed to explore the impact of EP, other than the anti-inflammatory and antiapoptotic functions, on the Th17/Treg balance via the JAK2/STAT3 pathway in a middle cerebral artery occlusion (MCAO)-induced model.

RESULTS

Fifty rats were randomly allocated into five groups, including the sham group (n = 10), EP+sham group (n = 10), MCAO group (n = 10), EP+MCAO group (n = 10), and EP+MCAO+JAK2/STAT3 pathway agonist (coumermycin A1, CA1) group (n = 10). The results indicated that EP alleviated neurological deficits, reduced infarct volume, and ameliorated neuronal apoptosis induced by MCAO. Additionally, the MCAO-induced Th17/Treg imbalance could be rectified by EP. The decreased levels of IL-10 and Foxp3 and increased IL-17 and RORα in the MCAO group were reversed by EP treatment. Regarding inflammation, EP reduced the concentrations of IL-6 and IL-17 and elevated those of IL-10 and TGF-β. The neuroprotective effects of EP were accompanied by decreased phosphorylation of JAK2 and STAT3. Furthermore, CA1 pretreatment diminished all the beneficial effects of EP partially.

CONCLUSION

Our findings suggest that EP contributes to attenuating neuronal apoptosis, Th17/Treg imbalance, and inflammation induced by MCAO via inhibiting the JAK2/STAT3 pathway, indicating its therapeutic potential in ischemic stroke.

Acupuncture regulates the Th17/Treg balance and improves cognitive deficits in a rat model of vascular dementia

Objective

The present study was developed to explore the impact of acupuncture on the Th17/Treg balance in the brain and the periphery and associated changes in cognitive deficits in a rat model of vascular dementia (VD).

Methods

Male Wistar rats (8 weeks old) were randomly assigned to sham-operated (Gs, n = 10), and operation (n = 30) groups. A VD model was established for all rats in the operation group via the permanent bilateral occlusion of the common carotid artery. Behavioral screening of these rats was conducted via a hidden platform trial at 2 months post-operation. These operation group rats were then further subdivided into impaired (Gi) and acupuncture (Ga) groups (n = 10/group). Acupuncture was performed over a 21-day period for rats in the Ga group. A Morris water maze (MWM) test was used to assess cognitive function for rats in all groups. Flow cytometry and fluorescent staining were used to detect Th17 and Treg cells in samples from these animals based on IL-17/FoxP3 or CD4+FoxP3+/CD4+RORγt+ staining profiles.

Results

Relative to the Gs group, escape latency values for rats in the Gi group were significantly increased. Following treatment, rats in the Ga group exhibited significant reductions in escape latency values as compared to rats in the Gi group (P < 0.05). The relative Treg proportion in the peripheral blood and spleen additionally trended upwards in these Ga rats as compared to those in the Gi group (P > 0.05), whereas the frequency of Th17 cells in the peripheral blood and spleen of Ga group rats trended downward relative to the Gi group (P > 0.05). Significantly fewer CD4+RORγt+ and RORγt+ cells were detected in the Ga group relative to the Gi group, whereas CD4+FoxP3+ and FoxP3+ cell counts were increased (P < 0.01).

Conclusion

In summary, VD model rats exhibited dysregulated Th17/Treg homeostasis. Acupuncture treatment was sufficient to reduce the frequency and numbers of Th17 cells in these animals while increasing Treg cell levels, thereby alleviating cognitive deficits with respect to both spatial learning and memory impairment. Consequently, the therapeutic benefits of such acupuncture treatment may be attributable to the regulation of the Th17/Treg balance and associated improvements in cognitive function.

Regulatory T Cells: Regulation of Identity and Function

T regulatory cells suppress a variety of immune responses to self-antigens and play a role in peripheral tolerance maintenance by limiting autoimmune disorders, and other pathological immune responses such as limiting immune reactivity to oncoprotein encoded antigens. Forkhead box P3 (FOXP3) expression is required for Treg stability and affects functional activity. Mutations in the master regulator FOXP3 and related components have been linked to autoimmune diseases in humans, such as IPEX, and a scurfy-like phenotype in mice. Several lines of evidence indicate that Treg use a variety of immunosuppressive mechanisms to limit an immune response by targeting effector cells, including secretion of immunoregulatory cytokines, granzyme/perforin-mediated cell cytolysis, metabolic perturbation, directing the maturation and function of antigen-presenting cells (APC) and secretion of extracellular vesicles for the development of immunological tolerance. In this review, several regulatory mechanisms have been highlighted and discussed.

A Novel CAR Expressing NK Cell Targeting CD25 With the Prospect of Overcoming Immune Escape Mechanism in Cancers

For many years, high-affinity subunit of IL-2 receptor (CD25) has been considered as a promising therapeutic target for different pathologic conditions like allograft rejection, autoimmunity, and cancers. Although CD25 is transiently expressed by newly-activated T cells, it is the hallmark of regulatory T (Treg) cells which are the most important immunosuppressive elements in tumor microenvironment. Thus, Tregs can be considered as a potential target for chimeric antigen receptor (CAR)-based therapeutic approaches. On the other hand, due to some profound adverse effects pertaining to the use of CAR T cells, CAR NK cells have caught researchers’ attention as a safer choice. Based on these, the aim of this study was to design and develop a CAR NK cell against CD25 as the most prominent biomarker of Tregs with the prospect of overcoming immune escape mechanism in solid and liquid cancers. In the current study, an anti-CD25 CAR was designed and evaluated by comprehensive in silico analyses. Then, using lentiviral transduction system, NK-92 cell line was engineered to express this anti-CD25 CAR construct. In vitro functional analyses of anti-CD25 CAR for its reactivity against CD25 antigen as well as for cytotoxicity and cytokine production assays against CD25 bearing Jurkat cell line were done. In silico analyses demonstrated that the anti-CD25 CAR transcript and scFv protein structures were stable and had proper interaction with the target. Also, in vitro analyses showed that the anti-CD25 CAR-engineered NK-92 cells were able to specifically detect and lyse target cells with an appropriate cytokine production and cytotoxic activity. To conclude, the results showed that this novel CAR NK cell is functional and warrant further investigations.

Salidroside regulates imbalance of Th17/Treg and promotes ischemic tolerance by targeting STAT-3 in cerebral ischemia-reperfusion injury

INTRODUCTION

The balance between Th17 and Treg cells controls the immune response and is an important regulator of helper T cells acting on autoimmune diseases. Focal cerebral ischemia-reperfusion injury can induce imbalance of Th17/Treg cells in the brain and the peripheral immune system of rats. The aim of this study was to investigate the effect of salidroside (Sal) on the ratio of Th17 and Treg cells in an adult rat model of middle cerebral artery occlusion (MCAO).

MATERIAL AND METHODS

Forty rats were divided into 4 groups: normal group, sham group, surgery group, and Sal group. After treatment, the neurological deficits in rats were evaluated. Peripheral blood mononuclear cells were isolated and the count of Th17 and Treg cells was detected by flow cytometry. The infarct size and expression of RORγt and Foxp3 were detected in rat brain tissue. Rat spleen cells were isolated, CD4⁺ T cells were purified by immunomagnetic beads. Treg cells were induced by adding cytokine TGF-β. Th17 cells were induced by adding cytokine IL-6. The expression of STAT-3 was inhibited by SiRNA, and the effect of Sal on the differentiation of Th17/Treg cells was analyzed. The expression levels of IL-6, TNF-α, MCP-1, STAT-3 and NF-κ-B2 proteins were examined.

RESULTS

The results show that MCAO can induce an imbalance of Th17 and Treg cells in peripheral blood of rats. Sal treatment can significantly reduce the neurological deficit and infarct size of MCAO rats, reverse the oxidative stress of rat brain tissue, and inhibit the apoptosis of brain cells in MCAO rats. In the brain tissue of MCAO rats, Sal could significantly inhibit the expression of IL-6, TNF-α, MCP-1, STAT-3 and NF-κ-B2. Down-regulation of STAT-3 significantly reversed the therapeutic effects of Sal treatment.

CONCLUSIONS

Our results indicate that Sal can increase the tolerance of rat brain tissue to ischemia, inhibit cell apoptosis and reduce oxidative stress by targeting STAT-3.

The deubiquitinase CYLD controls protective immunity against helminth infection by regulation of Treg cell plasticity

BACKGROUND

Type 2 immunity can be modulated by regulatory T (Treg) cell activity. It has been suggested that the deubiquitinase cylindromatosis (CYLD) plays a role in the development or function of Treg cells, implying that it could be important for normal protective immunity, where type 2 responses are prevalent.

OBJECTIVE

We sought to investigate the role of CYLD in Treg cell function and T_H2 cell immune responses under steady-state conditions and during helminth infection.

METHODS

Foxp3-restricted CYLD conditional knockout (KO) mice were examined in mouse models of allergen-induced airway inflammation and Nippostrongylus brasiliensis infection. We performed multiplex magnetic bead assays, flow cytometry, and quantitative PCR to understand how a lack of CYLD affected cytokine production, homing, and suppression in Treg cells. Target genes regulated by CYLD were identified and validated by microarray analysis, coimmunoprecipitation, short hairpin RNA knockdown, and transfection assays.

RESULTS

Treg cell-specific CYLD KO mice showed severe spontaneous pulmonary inflammation with increased migration of Treg cells into the lung. CYLD-deficient Treg cells furthermore produced high levels of IL-4 and failed to suppress allergen-induced lung inflammation. Supporting this, the conditional KO mice displayed enhanced protection against N brasiliensis infection by contributing to type 2 immunity. Treg cell conversion into IL-4-producing cells was due to augmented mitogen-activated protein kinase and nuclear factor κB signaling. Moreover, Scinderin, a member of the actin-binding gelsolin family, was highly upregulated in CYLD-deficient Treg cells, and controlled IL-4 production through forming complexes with mitogen-activated protein kinase kinase/extracellular receptor kinase. Correspondingly, both excessive IL-4 production in vivo and the protective role of CYLD-deficient Treg cells against N brasiliensis were reversed by Scinderin ablation.

CONCLUSIONS

Our findings indicate that CYLD controls type 2 immune responses by regulating Treg cell conversion into T_H2 cell-like effector cells, which potentiates parasite resistance.

Shikonin Controls the Differentiation of CD4+CD25+ Regulatory T Cells by Inhibiting AKT/mTOR Pathway

CD4⁺CD25⁺ regulatory T (Treg) cells maintain the function of immune tolerance and the balance of immune cells. Defects in the number and function of Treg cells can induce the development and progression of inflammatory disease. Shikonin, the main active ingredient of Lithospermum, has anti-inflammatory and anti-tumor effects. Shikonin is also an effective drug for the treatment of psoriasis, which is a chronic inflammatory skin disease. However, the underlying mechanism is not yet clear. To evaluate the role of shikonin on the induction of Treg cells, we tested the number and function of Treg cells in vivo and in vitro. Shikonin can effectively promote the differentiation of iTreg cells by inhibiting the AKT/mTOR pathway in vitro. Moreover, in vivo, intragastrically administered shikonin effectively improved lesions in mice with imiquimod-induced psoriasis and increased the number of iTreg cells in the spleen and their secretion. Shikonin significantly increases the expression of Foxp3mRNA in skin of the psorisic mice. Therefore, we expect that shikonin can prevent the development of inflammation and treat psoriasis by regulating iTreg cells. Novel ideas for the treatment of psoriasis are also proposed.

The role of regulatory T cells and genes involved in their differentiation in pathogenesis of selected inflammatory and neoplastic skin diseases. Part II: The Treg role in skin diseases pathogenesis

Regulatory FOXP3+ T cells (Tregs) constitute 5% to 10% of T cells in the normal human skin. They play an important role in the induction and maintenance of immunological tolerance. The suppressive effects of these cells are exerted by various mechanisms including the direct cytotoxic effect, anti-inflammatory cytokines, metabolic disruption, and modulation of the dendritic cells function. The deficiency of Treg cells number or function are one of the basic elements of the pathogenesis of many skin diseases, such as psoriasis, atopic dermatitis, bacterial and viral infections. They also play a role in the pathogenesis of T cell lymphomas of the skin (cutaneous T cell lymphomas - CTCL), skin tumors and mastocytosis. Here, in the second part of the cycle, we describe dysfunctions of Tregs in selected skin diseases.

Detection and Significance of CD4+CD25+CD127dim Regulatory T Cells in Individuals with Severe Aplastic Anemia

Objective:

To investigate the relationship between CD4+CD25+CD127dim regulatory T cells (Tregs) and immune imbalance in acquired severe aplastic anemia (SAA).

Materials and Methods:

The quantity of CD4+CD25+CD127dim Tregs in 44 SAA patients and 23 normal controls was measured by flow cytometry. Correlations between Tregs and T cell subsets, dendritic cell (DC) subsets, granulocyte counts, and percentage of reticulocytes (RET%) were analyzed.

Results:

The percentage of CD4+CD25+CD127dim Tregs in peripheral blood lymphocytes (PBLs) of untreated patients was lower than in recovery patients and normal controls (0.83±0.44% vs. 2.91±1.24% and 2.18±0.55%, respectively, p<0.05). The percentage of CD4+CD25+CD127dim Tregs in CD4+ T lymphocytes of recovery patients was higher than that of untreated patients and normal controls (9.39±3.51% vs. 7.61±5.3% and 6.83±1.4%, respectively, p<0.05). The percentage of CD4+ T lymphocytes in PBLs of untreated patients was lower than in recovery patients and normal controls (13.55±7.37% vs. 31.82±8.43% and 32.12±5.88%, respectively, p<0.05). T cell subset (CD4+/CD8+ ratio) was 0.41±0.24 in untreated patients, which was lower than in recovery patients (1.2±0.4) and normal controls (1.11±0.23) (p<0.05). DC subset (myeloid DC/plasmacytoid DC ratio, DC1/DC2 ratio) was 3.08±0.72 in untreated patients, which was higher than in recovery patients (1.61±0.49) and normal controls (1.39±0.36) (p<0.05). The percentage of CD4+CD25+CD127dim Tregs in PBLs was positively associated with T cell subset (r=0.955, p<0.01) and negatively associated with DC subset (r=-0.765, p<0.01). There were significant positive correlations between CD4+CD25+CD127dim Tregs/PBL and granulocyte counts and RET% (r=0.739 and r=0.749, respectively, p<0.01).

Conclusion:

The decrease of CD4+CD25+CD127dim Tregs in SAA patients may cause excessive functioning of T lymphocytes and thus lead to hematopoiesis failure in SAA.

CD4(+)HLA-G(+) regulatory T cells: Molecular signature and pathophysiological relevance

The regulation of potentially harmful immune responses by regulatory T (Treg) cells is essential for maintaining peripheral immune tolerance and homeostasis. Especially CD4(+) Treg cells have been regarded as pivotal regulators of autoreactive and inflammatory responses as well as inducers of immune tolerance by using a variety of immune suppressive mechanisms. Besides the well-known classical CD4(+)CD25(+)FoxP3(+) Treg cells, CD4(+) T cells expressing the immune tolerizing molecule human leukocyte antigen G (HLA-G) have been recently described as another potent thymus-derived Treg (tTreg) cell subset. Albeit both tTreg subsets share common molecular characteristics, the mechanisms of their immunosuppressive function differ fundamentally. Dysfunction and numerical abnormalities of classical CD4(+) tTreg cells have been implicated in the pathogenesis of several immune-mediated diseases such as multiple sclerosis (MS). Clearly, a deeper understanding of the various CD4(+) tTreg subsets and also the underlying mechanisms of impaired immune tolerance in these disorders are essential for the development of potential therapeutic strategies. This review focuses on the current knowledge on defining features and functioning of HLA-G(+)CD4(+) tTreg cells as well as their emerging role in various pathologies with special emphasis on the pathogenesis of MS. Furthermore, future research possibilities together with potential therapeutic applications are discussed.

Translating Treg Therapy in Humanized Mice

Regulatory T cells (Treg) control immune cell function as well as non-immunological processes. Their far-reaching regulatory activities suggest their functional manipulation as a means to sustainably and causally intervene with the course of diseases. Preclinical tools and strategies are however needed to further test and develop interventional strategies outside the human body. “Humanized” mouse models consisting of mice engrafted with human immune cells and tissues provide new tools to analyze human Treg ontogeny, immunobiology, and therapy. Here, we summarize the current state of humanized mouse models as a means to study human Treg function at the molecular level and to design strategies to harness these cells for therapeutic purposes.

Human umbilical vein endothelial cells promote the inhibitory activation of CD4(+)CD25(+)Foxp3(+) regulatory T cells via PD-L1

BACKGROUND

Atherosclerosis (AS) is a chronic inflammation characterized by massive infiltration of inflammatory cells in arterial wall plaques. Programmed death ligand-1 (PD-L1), a co-stimulatory molecule, plays a vital role in regulating immune responses. We investigated the role and mechanisms of PD-L1 expressed on oxidized low-density lipoprotein (ox-LDL)-impaired human umbilical vein endothelial cells (HUVECs) in promoting activation and cytokine production of CD4(+)CD25(+) forkhead box P3 (FoxP3) regulatory T cells (Tregs).

METHODS AND RESULTS

Tregs were incubated alone, with HUVECs or HUVECs pre-stimulated with ox-LDL in the presence of anti-CD3 monoclonal antibodies (mAbs) for 48 h. HUVECs were shown to upregulate the immune phenotypic markers of Tregs, such as glucocorticoid-induced TNF receptor (GITR), cytotoxic T lymphocyte antigen-4 (CTLA-4) and programmed cell death-1 protein (PD-1). Moreover, HUVECs modulated cytokine production of Tregs (e.g., interleukin-10 (IL-10) and transforming growth factor-β1 (TGF-β1)). HUVECs treated with anti-PD-L1 mAbs were unable to regulate the surface expression and cytokine production of Tregs. The Transwell culture system suggested that interaction between HUVECs and Tregs via PD-L1 requires cell-to-cell contact.

CONCLUSION

Expression of the negative co-stimulatory molecule PD-L1 on HUVECs may upregulate the inhibitory activation and cytokine production of CD4(+)CD25(+)Foxp3(+) regulatory T cells in AS.

Characteristics of the peripheral T cell immune response of patients at different stages of vascular cognitive impairment

AIM

To investigate the characteristics of the peripheral T cell immune response of patients at different stages of vascular cognitive impairment (VCI).

METHODS

61 Arterial atherosclerotic cerebral infarct induced VCI patients, including 28 vascular dementia (VaD) cases, 33 no dementia (VCI-ND) cases, and 25 atherosclerotic cerebral infarct patients with normal cognitive function (CI-NC) as controls were enrolled. Peripheral CD8(+)T, CD4(+)CD25(+) Treg, CD4(+)IL-17(+) Th17 cells proportion, and IL-1β, IL-2, IL-6, IFN-γ levels, and neuropsychological function were assessed.

RESULTS

There was no difference in average age, gender ratio, years of education, and risk factors of infarct among the three groups. Peripheral CD4(+)CD25(+) Treg in VCI-ND and VaD groups were significantly lower than that in controls, and CD8(+) T cells were markedly elevated in VaD group. The IL-17(+) Th17 cell proportion did not differ significantly among three groups. IL-6 and IFN-γ expression levels in VaD group were higher than those in other two groups. The VDAS-Cog executive function subscale score was negatively correlated with CD4(+)CD25(+) Treg proportion in VCI patients, and positively correlated with IL-6 levels.

CONCLUSION

VCI patients demonstrated a decrease in peripheral CD4(+) Treg proportion and increased IL-6 expression, and both parameters were correlated with the decline of executive functions.

Interferon-Beta Therapy of Multiple Sclerosis Patients Improves the Responsiveness of T Cells for Immune Suppression by Regulatory T Cells

Multiple sclerosis (MS) is an inflammatory autoimmune disease characterized by imbalanced immune regulatory networks, and MS patient-derived T effector cells are inefficiently suppressed through regulatory T cells (Treg), a phenomenon known as Treg resistance. In the current study we investigated T cell function in MS patients before and after interferon-beta therapy. We compared cytokine profile, responsiveness for Treg-mediated suppression ex vivo and evaluated reactivity of T cells in vivo using a humanized mouse model. We found that CD4⁺ and CD8⁺ T cells of therapy-naive MS patients were resistant to Treg-mediated suppression. Treg resistance is associated with an augmented IL-6 production, enhanced IL-6 receptor expression, and increased PKB/c-Akt phosphorylation. These parameters as well as responsiveness of T cells to Treg-mediated suppression were restored after interferon-beta therapy of MS patients. Following transfer into immunodeficient mice, MS T cells induced a lethal graft versus host disease (GvHD) and in contrast to T cells of healthy volunteers, this aggressive T cell response could not be controlled by Treg, but was abolished by anti-IL-6 receptor antibodies. However, magnitude and lethality of GvHD induced by MS T cells was significantly decreased after interferon-beta therapy and the reaction was prevented by Treg activation in vivo. Our data reveals that interferon-beta therapy improves the immunoregulation of autoaggressive T effector cells in MS patients by changing the IL-6 signal transduction pathway, thus restoring their sensitivity to Treg-mediated suppression.

The immunopathogenesis of psoriasis

Psoriasis vulgaris is a chronic inflammatory skin disease that results from the complex interplay between keratinocytes, dendritic cells, and T cells. Keratinocytes trigger innate and adaptive immune responses. Dermal myeloid dendritic cells regulate T cell activation and production of cytokines and chemokines that amplify inflammation. Most of the psoriatic T cells discretely produce interferon-γ, interleukin (IL)-17, and IL-22. The initiation phase of psoriasis involves Toll-like receptors, antimicrobial peptide LL37, and plasmacytoid dendritic cells. Keratinocytes are the main cutaneous cell type expressing IL-17 receptors and hence the immune circuit is amplified by keratinocytes upregulating mRNAs for a range of inflammatory products.

Distribution of Peripheral Lymphocyte Populations in Primary Sjögren's Syndrome Patients

Purpose of this study was to evaluate the lymphocyte populations' distribution changes in peripheral blood of patients with primary Sjögren's syndrome (pSS). Lymphocyte populations' distribution changes in peripheral blood of pSS patients were investigated in 52 patients with pSS and in 28 healthy controls by flow cytometry. We found decreased absolute count of CD3⁺ T cell population in pSS patients. Analysis of CD4⁺ T cell population showed significant proportion and absolute count differences in pSS patient's blood with SSA/SSB antibodies (Abs) in comparison to controls. No significant differences were observed analyzing CD4⁺ and CD8⁺ Treg subpopulation. Proportion and absolute counts of Th17 cells were significantly lower in pSS patient's blood. Absolute counts of CD8⁺ T cells were significantly lower in pSS patients in comparison to controls and also impaired proportion and absolute counts of CD8⁺ subpopulations according to CD27⁺ and CD57⁺ were observed. Absolute counts of NKT and NK cells were decreased in pSS with Abs. B cells proportion was increased only in blood of pSS with Abs. Lymphocyte distribution impairment can be due to genetically determined lymphopenia or lymphocyte migration from periphery to inflammatory sites or/and increased susceptibility to apoptosis.

Attenuation of peripheral regulatory T-cell suppression of skin-homing CD8⁺T cells in atopic dermatitis

PURPOSE

Cutaneous lymphocyte-associated antigen (CLA)-expressing CD8⁺T cells have been known to play an important role in the pathogenesis of atopic dermatitis (AD). However, the mechanisms underlying the loss of self-tolerance remain unclear. Regulatory T cells (Tregs) play a key role in the development of homeostasis in the immune system. We, therefore, hypothesized that a reduced ability of Tregs to inhibit autologous CD8⁺CLA⁺T cells might be underlying mechanism in AD.

MATERIALS AND METHODS

CD8⁺CLA⁺T cells and Tregs were obtained from the peripheral blood of AD patients and control volunteers. The frequencies of CD8⁺CLA⁺T cells were evaluated. The proliferative responses of CD8⁺CLA⁺T cells were assessed by flow cytometry, and the levels of transforming growth factor-β1 (TGF-β1) and interleukin-10 (IL-10) in culture supernatants were detected by enzyme-linked immunosorbent assay.

RESULTS

Our results revealed higher frequency and increased expression of perforin and granzyme-B in peripheral CD8⁺CLA⁺T cells in AD, and lower inhibitory ability of Tregs on proliferation of CD8⁺CLA⁺T cells in AD. Meanwhile, the levels of TGF-β1 produced by Tregs were significantly lower in AD, and anti-TGF-β1 abolished such suppression.

CONCLUSION

The attenuated inhibitory ability of Tregs on hyper-activated autologous CD8⁺CLA⁺T cells, mediated by TGF-β1, plays an important role in the pathogenesis of AD.

Adaptive immunity to fungi

Life-threatening fungal infections have risen sharply in recent years, owing to the advances and intensity of medical care that may blunt immunity in patients. This emerging crisis has created the growing need to clarify immune defense mechanisms against fungi with the ultimate goal of therapeutic intervention. We describe recent insights in understanding the mammalian immune defenses that are deployed against pathogenic fungi. We focus on adaptive immunity to the major medically important fungi and emphasize three elements that coordinate the response: (1) dendritic cells and subsets that are mobilized against fungi in various anatomical compartments; (2) fungal molecular patterns and their corresponding receptors that signal responses and shape the differentiation of T-cell subsets and B cells; and, ultimately (3) the effector and regulatory mechanisms that eliminate these invaders while constraining collateral damage to vital tissue. These insights create a foundation for the development of new, immune-based strategies for prevention or enhanced clearance of systemic fungal diseases.

CD4(+) NKG2D(+) T cells induce NKG2D down-regulation in natural killer cells in CD86-RAE-1ε transgenic mice

The binding of NKG2D to its ligands strengthens the cross-talk between natural killer (NK) cells and dendritic cells, particularly at early stages, before the initiation of the adaptive immune response. We found that retinoic acid early transcript-1ε (RAE-1ε), one of the ligands of NKG2D, was persistently expressed on antigen-presenting cells in a transgenic mouse model (pCD86-RAE-1ε). By contrast, NKG2D expression on NK cells, NKG2D-dependent cytotoxicity and tumour rejection, and dextran sodium sulphate-induced colitis were all down-regulated in this mouse model. The down-regulation of NKG2D on NK cells was reversed by stimulation with poly (I:C). The ectopic expression of RAE-1ε on dendritic cells maintained NKG2D expression levels and stimulated the activity of NK cells ex vivo, but the higher frequency of CD4(+) NKG2D(+) T cells in transgenic mice led to the down-regulation of NKG2D on NK cells in vivo. Hence, high levels of RAE-1ε expression on antigen-presenting cells would be expected to induce the down-regulation of NK cell activation by a regulatory T-cell subset.

Human CD4+ HLA-G+ regulatory T cells are potent suppressors of graft-versus-host disease in vivo

CD4(+) T cells expressing the immunotolerizing molecule HLA-G have been described as a unique human thymus-derived regulatory T (tTreg) cell subset involved in immunoregulation and parenchymal homeostasis during infectious and autoimmune inflammation. We compared properties and molecular characteristics of human CD4(+)HLA-G(+) with those of CD4(+)CD25(+)FoxP3-expressing tTreg cells using in vitro studies of T-cell receptor (TCR) signaling, single-cell electrophysiology, and functional in vivo studies. Both tTreg populations are characterized by alterations in proximal-signaling pathways on TCR stimulation and a hyperpolarization of the plasma membrane when compared to conventional CD4(+) T cells. However, both clearly differ in phenotype and pattern of secreted cytokines, which results in distinct mechanisms of suppression: While CD4(+)HLA-G(+) cells secrete high levels of inhibitory molecules (IL-10, soluble HLA-G, IL-35), CD4(+)CD25(+)FoxP3(+) cells express these molecules at significantly lower levels and seem to exert their function mainly in a contact-dependent manner via cyclic adenosine-monophosphate. Finally we demonstrate that human CD4(+)HLA-G(+) tTreg cells significantly ameliorated graft-versus-host disease in a humanized mouse model as a first proof of their in vivo relevance. Our data further characterize and establish CD4(+)HLA-G(+) cells as a potent human tTreg population that can modulate polyclonal adaptive immune responses in vivo and thus being a promising candidate for potential clinical applications in the future.

Harnessing regulatory T cells for clinical use in transplantation: the end of the beginning

Owing to the adverse effects of immunosuppression and an inability to prevent chronic rejection, there is a pressing need for alternative strategies to control alloimmunity. In three decades, regulatory T cells (Tregs) have evolved from a hypothetical mediator of adoptively transferred tolerance to a well-defined population that can be expanded ex vivo and returned safely to patients in clinical trials. Herein, we review the historical developments that have permitted these advances and the current status of clinical trials examining Tregs as a cellular therapy in transplantation. We conclude by discussing the critical unanswered questions that face this field in the coming years.

A case of psoriasis accompanied by arthritis after delivery

Psoriasis and psoriatic arthritis are chronic inflammatory diseases of the skin and joints, but the relationship between them has not been fully understood. Since the delay of treatment for psoriatic arthritis can result in the severe deformities, it is important to identify the pathological triggers of the arthritis. On the other hand, many reports suggest that the changes of immune balance during pre/postpartum period are associated with the state of autoimmune diseases. Here, we report a female case with psoriasis whose arthritis may be triggered by the delivery. Our report suggests that immune tolerance may diminish in the postpartum period, which may alter the susceptibility to arthritis. Female patients should be followed-up carefully during postpartum period against the development of arthritis.

Immunology of psoriasis

The skin is the front line of defense against insult and injury and contains many epidermal and immune elements that comprise the skin-associated lymphoid tissue (SALT). The reaction of these components to injury allows an effective cutaneous response to restore homeostasis. Psoriasis vulgaris is the best-understood and most accessible human disease that is mediated by T cells and dendritic cells. Inflammatory myeloid dendritic cells release IL-23 and IL-12 to activate IL-17-producing T cells, Th1 cells, and Th22 cells to produce abundant psoriatic cytokines IL-17, IFN-γ, TNF, and IL-22. These cytokines mediate effects on keratinocytes to amplify psoriatic inflammation. Therapeutic studies with anticytokine antibodies have shown the importance of the key cytokines IL-23, TNF, and IL-17 in this process. We discuss the genetic background of psoriasis and its relationship to immune function, specifically genetic mutations, key PSORS loci, single nucleotide polymorphisms, and the skin transcriptome. The association between comorbidities and psoriasis is reviewed by correlating the skin transcriptome and serum proteins. Psoriasis-related cytokine-response pathways are considered in the context of the transcriptome of different mouse models. This approach offers a model for other inflammatory skin and autoimmune diseases.

Up-regulation of microRNA-210 induces immune dysfunction via targeting FOXP3 in CD4(+) T cells of psoriasis vulgaris

Psoriasis vulgaris (PV) is a chronic inflammatory and T cell-mediated autoimmune skin disease. An immune dysfunction that is manifested by abnormally activated T cells and defective regulatory T (Treg) cells may play an important role in the pathogenesis of PV. However, the precise mechanism of the immune dysfunction in PV patients still remains unclear. In this study, we found that miR-210 expression is increased significantly in CD4(+) T cells from patients with PV and confirmed that FOXP3 is a target gene of miR-210. We also found that overexpression of miR-210 inhibits FOXP3 expression and impairs the immunosuppressive functions of Treg cells in CD4(+) T cells from healthy controls. In contrast, inhibition of miR-210 increases FOXP3 expression and reverses the immune dysfunction in CD4(+) T cells from patients with PV. Our data demonstrates that increased miR-210 induces immune dysfunction via by FOXP3 in CD4(+) T cells from patients with PV.

Kinetics of IL-6 production defines T effector cell responsiveness to regulatory T cells in multiple sclerosis

In multiple sclerosis (MS) autoaggressive T effector cells (Teff) are not efficiently controlled by regulatory T cells (Treg) but the underlying mechanisms are incompletely understood. Proinflammatory cytokines are key factors facilitating Teff activity in chronic inflammation. Here we investigated the influence of IL-6 on Treg sensitivity of Teff from therapy-naïve MS patients with or without active disease. Compared to healthy volunteers and independent of disease course CD4⁺ and especially CD8⁺ MS-Teff were insensitive against functional active Treg from healthy controls. This unresponsiveness was caused by accelerated production of IL-6, elevated IL-6 receptor expression and phosphorylation of protein kinase B (PKB)/c-Akt in MS-Teff. In a positive feedback loop, IL-6 itself induced its accelerated synthesis and enhanced phosphorylation of PKB/c-Akt that finally mediated Treg resistance. Furthermore, accelerated IL-6 release especially by CD8⁺ Teff prevented control of surrounding Teff, described here as “bystander resistance”. Blockade of IL-6 receptor signaling or direct inhibition of PKB/c-Akt phosphorylation restored Treg responsiveness of Teff and prevented bystander resistance. In Teff of healthy controls (HC) exogenous IL-6 also changed the kinetics of IL-6 production and induced Treg unresponsiveness. This modulation was only transient in Teff from healthy volunteers, whereas accelerated IL-6 production in MS-Teff maintained also in absence of IL-6. Hence, we showed that the kinetics of IL-6 production instead of elevated IL-6 levels defines the Teff responsiveness in early Treg-T cell communication in MS independent of their disease course and propose IL-6 and associated PKB/c-Akt activation as effective therapeutic targets for modulation of Teff activity in MS.

Mesenchymal stem cells (MSCs) from scleroderma patients (SSc) preserve their immunomodulatory properties although senescent and normally induce T regulatory cells (Tregs) with a functional phenotype: implications for cellular-based therapy

Systemic sclerosis (SSc) is a chronic disease, with early activation of the immune system. The aim of our work was to address how SSc-mesenchymal stem cells (MSCs), although senescent, might preserve specific immunomodulatory abilities during SSc. MSCs were obtained from 10 SSc patients and 10 healthy controls (HC). Senescence was evaluated by assessing cell cycle, β-galactosidase (β-Gal) activity, p21 and p53 expression; doxorubicin was used as acute senescence stimulus to evaluate their ability to react in stressed conditions. Immunomodulatory abilities were studied co-culturing MSCs with peripheral blood mononuclear cells (PBMCs) and CD4(+) cells, in order to establish both their ability to block proliferation in mixed lymphocyte reaction and in regulatory T cells (Tregs) induction. SSc-MSC showed an increase of senescence biomarkers. Eighty per cent of MSCs were in G0-G1 phase, without significant differences between SSc and HC. SSc-MSCs showed an increased positive β-Gal staining and higher p21 transcript level compared to HC cells. After doxorubicin, β-Gal staining increased significantly in SSc-MSCs. On the contrary, doxorubicin abolished p21 activation and elicited p53 induction both in SSc- and HC-MSCs. Interleukin (IL)-6 and transforming growth factor (TGF)-β-related transcripts and their protein levels were significantly higher in SSc-MSCs. The latter maintained their immunosuppressive effect on lymphocyte proliferation and induced a functionally regulatory phenotype on T cells, increasing surface expression of CD69 and restoring the regulatory function which is impaired in SSc. Increased activation of the IL-6 pathway observed in our cells might represent an adaptive mechanism to senescence, but preserving some specific cellular functions, including immunosuppression.

Peripheral Th17/Treg imbalance in patients with atherosclerotic cerebral infarction

OBJECTIVE

CD4(+)CD25(+) regulatory T (Treg) cells and Th17 cells play important roles in peripheral immunity. Oxidized low-density lipoprotein (ox-LDL) is an instrumental factor in atherogenesis. However, the changes of Th17/Treg cells in patients with acute cerebral Infarction (ACI) and impact on Th17/Treg by ox-LDL are not clear. Here, we examined the balance of Th17/Treg in ACI patients and the effect of ox-LDL on this balance.

MATERIALS AND METHODS

The frequencies of Th17 and Treg cells, key transcription factors and relevant cytokines were examined in patients with ACI, Transient ischemic attack (TIA) and controls. The correlations of cytokines, inflammatory biomarkers and ox-LDL in serum to Th17/Treg frequency, and the effects of ox-LDL on Th17/Treg cells in vitro were analyzed.

RESULTS

ACI patients have shown a significant increase of Th17 frequency, RORγt expression and Th17 related cytokines (IL-17 and IL-6 ) levels, and a clear decline of Treg frequency, Foxp3 expression, suppressive function and regulatory cytokines (IL-10 and TGF-β1) levels. Furthermore, TIA patients also have notable variation as compared to control group. Serum ox-LDL and inflammatory biomarkers were positively correlated with the frequency of Th17 cells and negatively correlated with the frequency of Treg cells. Treg and Th17 cells from ACI patients were significantly susceptible to ox-LDL-mediated alterations in vitro.

CONCLUSIONS

Th17/Treg cells were imbalanced in ACI patients, and ox-LDL may contribute to this imbalance and lead to the occurrence of ACI suggesting their pathogenetic role in ACI.

Partial deficiency of sphingosine-1-phosphate lyase confers protection in experimental autoimmune encephalomyelitis

Background

Sphingosine-1-phosphate (S1P) regulates the egress of T cells from lymphoid organs; levels of S1P in the tissues are controlled by S1P lyase (Sgpl1). Hence, Sgpl1 offers a target to block T cell-dependent inflammatory processes. However, the involvement of Sgpl1 in models of disease has not been fully elucidated yet, since Sgpl1 KO mice have a short life-span.

Methodology

We generated inducible Sgpl1 KO mice featuring partial reduction of Sgpl1 activity and analyzed them with respect to sphingolipid levels, T-cell distribution, and response in models of inflammation.

Principal Findings

The partially Sgpl1 deficient mice are viable but feature profound reduction of peripheral T cells, similar to the constitutive KO mice. While thymic T cell development in these mice appears normal, mature T cells are retained in thymus and lymph nodes, leading to reduced T cell numbers in spleen and blood, with a skewing towards increased proportions of memory T cells and T regulatory cells. The therapeutic relevance of Sgpl1 is demonstrated by the fact that the inducible KO mice are protected in experimental autoimmune encephalomyelitis (EAE). T cell immigration into the CNS was found to be profoundly reduced. Since S1P levels in the brain of the animals are unchanged, we conclude that protection in EAE is due to the peripheral effect on T cells, leading to reduced CNS immigration, rather than on local effects in the CNS.

Significance

The data suggest Sgpl1 as a novel therapeutic target for the treatment of multiple sclerosis.

The Role of Inflammatory Cytokines, the RANKL/OPG Axis, and the Immunoskeletal Interface in Physiological Bone Turnover and Osteoporosis

Although it has long been recognized that inflammation, a consequence of immune-driven processes, significantly impacts bone turnover, the degree of centralization of skeletal and immune functions has begun to be dissected only recently. It is now recognized that formation of osteoclasts, the bone resorbing cells of the body, is centered on the key osteoclastogenic cytokine, receptor activator of NF- κ B ligand (RANKL). Although numerous inflammatory cytokines are now recognized to promote osteoclast formation and skeletal degradation, with just a few exceptions, RANKL is now considered to be the final downstream effector cytokine that drives osteoclastogenesis and regulates osteoclastic bone resorption. The biological activity of RANKL is moderated by its physiological decoy receptor, osteoprotegerin (OPG). New discoveries concerning the sources and regulation of RANKL and OPG in physiological bone turnover as well as under pathological (osteoporotic) conditions continue to be made, opening a window to the complex regulatory processes that control skeletal integrity and the depth of integration of the skeleton within the immune response. This paper will examine the interconnection between bone turnover and the immune system and the implications thereof for physiological and pathological bone turnover.

Assessment of sperm antigen specific T regulatory cells in women with recurrent miscarriage

BACKGROUND AND AIMS

The prevalence of recurrent miscarriage (RM) is about 1-3% of women; the pathogenesis of RM is not fully understood yet. This study aims to assess the sperm antigen specific regulatory T cells (Treg) in women with RM.

METHODS

A group of women with RM was recruited into this study. The sperm antigen was extracted from the semen samples of each woman's husband. The sperm antigen specific T cell response was assessed by flow cytometry.

RESULTS

Low frequency of sperm specific Tregs and high frequency of T helper (Th)1 cells were detected in RM women as compared with women without RM. The sperm specific Tregs in RM women expressed less Ubc13. Knockdown of Ubc13 from Tregs converted the Tregs to effector T cells.

CONCLUSIONS

Immune deregulation may play an important role in RM.

Probiotic therapy as a novel approach for allergic disease

The prevalence of allergic disease has increased dramatically in Western countries over the past few decades. The hygiene hypothesis, whereby reduced exposure to microbial stimuli in early life programs the immune system toward a Th2-type allergic response, is suggested to be a major mechanism to explain this phenomenon in developed populations. Such microbial exposures are recognized to be critical regulators of intestinal microbiota development. Furthermore, intestinal microbiota has an important role in signaling to the developing mucosal immune system. Intestinal dysbiosis has been shown to precede the onset of clinical allergy, possibly through altered immune regulation. Existing treatments for allergic diseases such as eczema, asthma, and food allergy are limited and so the focus has been to identify alternative treatment or preventive strategies. Over the past 10 years, a number of clinical studies have investigated the potential of probiotic bacteria to ameliorate the pathological features of allergic disease. This novel approach has stemmed from numerous data reporting the pleiotropic effects of probiotics that include immunomodulation, restoration of intestinal dysbiosis as well as maintaining epithelial barrier integrity. In this mini-review, the emerging role of probiotics in the prevention and/or treatment of allergic disease are discussed with a focus on the evidence from animal and human studies.