Suppressor Function Research Articles

Oral tolerance to dietary antigens and Foxp3+ regulatory T cells.

Immune tolerance to foods develops in the intestine upon food ingestion and is essential to prevent IgE-mediated food allergy and gut inflammation. In homeostasis, the intestine is a tolerogenic environment that favors the formation of food-specific Foxp3+ regulatory T cells. A tolerogenic intestinal environment depends on colonization by diverse microbiota and exposure to solid foods at a critical period in early life. These early immune responses lead to the induction of antigen-specific Foxp3+ regulatory T cells in draining mesenteric lymph nodes. These peripherally induced regulatory cells circulate and seed the lamina propria of the gut, exerting suppressive function systemically and locally in the intestine. Successful establishment of a tolerogenic intestinal environment in early life sets the stage for oral tolerance to new antigens in adult life.

Inflammatory factor-mediated miR-155/SOCS1 signaling axis leads to Treg impairment in systemic lupus erythematosus

BackgroundSystemic lupus erythematosus (SLE) is an autoimmune disorder associated with the decrease and functional impairment of regulatory T cells (Tregs). In the current study, we explored the interplay of miR-155 and suppressor of cytokine signaling 1 (SOCS1) in regulating Treg function and stability in SLE. MethodsClinical samples from healthy subjects and SLE patients were collected, and a mouse model of SLE was established to profile the expression pattern of miR-155 and SCOS1 in Tregs. Tregs isolated from mouse spleen were stimulated by inflammatory cytokines to confirm involvement of miR-155/SOCS1 axis in dictating Treg stability and function. We also administrated synthetic miR-155 inhibitor in SLE animal model to evaluate the potential effect on rescuing Treg function and alleviating SLE progression. ResultsTregs from SLE patients and SLE-induced mice exhibited a downregulation of SOCS1 and an upregulation of miR-155. In Tregs stimulated by inflammatory cytokines, Nuclear factor kappa B (NF-κB) signaling activation was required for the change of SOCS1 and miR-155 expression. miR-155 served as a negative regulator to dampen SOCS1 expression in inflammation-stimulated Tregs. The transfection of miR-155 mimic impaired the suppressive function and differentiation of Tregs through targeting SOCS1. In contrast, miR-155 inhibition improved Treg function under inflammatory stimulation and alleviated SLE conditions in the mouse model. ConclusionInflammation-induced miR-155 impairs Treg stability and function in SLE through decreasing SOCS1 expression. Targeting miR-155 might be developed as an intervention to mitigate SLE conditions.

Acidity induces durable enhancement of Treg cell suppressive functions for tumor immune evasion

The microenvironment within solid tumors often becomes acidic due to various factors associated with abnormal metabolism and cellular activities, including increased lactate production as a result of dysregulated tumor glycolysis. Recently, we have identified multiple tumor microenvironment (TME) factors that potentiate regulatory T (Treg) cell function in evading anti-tumor immunosurveillance. Despite the strong correlation between lactate and acidity, the potential roles of acidity in intratumoral Treg cell adaptation and underlying molecular mechanisms have gone largely unstudied. In this study, we demonstrate that acidity significantly enhances immunosuppressive functions of nTreg cells, but not iTreg cells, without altering the expression of either FoxP3 or the cell surface receptors CD25, CTLA4, or GITR in these cells. Surprisingly, the addition of lactate, often considered a major contributor to increased acidity of the TME, completely abolished the acidity-induced enhancement of nTreg suppressive functions. Consistently, metabolic flux analyses showed elevated basal mitochondrial respiratory capacity and ATP-coupled respiration in acidity-treated nTreg cells without altering glycolytic capacity. Genome-wide transcriptome and metabolomics analyses revealed alterations in multiple metabolic pathways, particularly the one-carbon folate metabolism pathway, with reduced SAM, folate, and glutathione, in nTreg cells exposed to low pH conditions. Addition of a one-carbon metabolic contributor, formate, diminished the acidity-induced enhancement in nTreg cell suppressive functions, but neither SAM nor glutathione could reverse the phenotype. Remarkably, in vitro transient treatment of nTreg cells resulted in sustained enhancement of their functions, as evidenced by more vigorous tumor growth observed in mice adoptively receiving acidity-treated nTreg cells. Further analysis of intratumoral infiltrated T cells confirmed a significant reduction in CD8+ T cell frequency and their granzyme B production. In summary, our study elucidates how acidity-mediated metabolic reprogramming leads to sustained Treg-mediated tumor immune evasion.

Lemon zinc finger protein ClSUP induces the accumulation of reactive oxygen species and inhibits citrus yellow vein-clearing virus infection via interactions with ClDOF3.4.

Citrus yellow vein-clearing virus (CYVCV) is an increasing threat to citrus cultivation. Notably, the role of zinc finger proteins (ZFPs) in mediating viral resistance in citrus plants is unclear. In this study, we demonstrate that ZFPs ClSUP and ClDOF3.4 enhance citrus defense responses against CYVCV in Eureka lemon. ClSUP interacted with the coat protein (CP) of CYVCV to reduce CP accumulation and inhibit its silencing suppressor function. Overexpression of CISUP triggered reactive oxygen species (ROS) and salicylic acid (SA) pathways, and enhanced resistance to CYVCV infection. In contrast, ClSUP-silencing resulted in increased CP accumulation and down-regulated ROS and SA-related genes. ClDOF3.4 interacts with ClSUP to facilitate its interactions with CP. Furthermore, ClDOF3.4 synergistically regulated the accumulation of ROS and SA with ClSUP and accelerated the down-regulation of CP accumulation. Transgenic plants co-expressing ClSUP and ClDOF3.4 remarkedly decrease the CYVCV. These findings provide a new reference for understanding the interaction mechanism between the host and CYVCV.

Platelet-activating factor (PAF) promotes immunosuppressive neutrophil differentiation within tumors

Chronic inflammatory milieu in the tumor microenvironment (TME) leads to the recruitment and differentiation of myeloid-derived suppressor cells (MDSCs). Polymorphonuclear (PMN)-MDSCs, which are phenotypically and morphologically defined as a subset of neutrophils, cause major immune suppression in the TME, posing a significant challenge in the development of effective immunotherapies. Despite recent advances in our understanding of PMN-MDSC functions, the mechanism that gives rise to immunosuppressive neutrophils within the TME remains elusive. Both in vivo and in vitro, newly recruited neutrophils into the tumor sites remained activated and highly motile for several days and developed immunosuppressive phenotypes, as indicated by increased arginase 1 (Arg1) and dcTrail-R1 expression and suppressed anticancer CD8 T cell cytotoxicity. The strong suppressive function was successfully recapitulated by incubating naive neutrophils with cancer cell culture supernatant in vitro. Cancer metabolite secretome analyses of the culture supernatant revealed that both murine and human cancers released lipid mediators to induce the differentiation of immunosuppressive neutrophils. Liquid chromatography-mass spectrometry (LC-MS) lipidomic analysis identified platelet-activation factor (PAF; 1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine) as a common tumor-derived lipid mediator that induces neutrophil differentiation. Lysophosphatidylcholine acyltransferase 2 (LPCAT2), the PAF biosynthetic enzyme, is up-regulated in human pancreatic ductal adenocarcinoma (PDAC) and shows an unfavorable correlation with patient survival across multiple cancer types. Our study identifies PAF as a lipid-driven mechanism of MDSC differentiation in the TME, providing a potential target for cancer immunotherapy.

LINC01503 promotes the cell proliferation, migration and invasion of triple-negative breast cancer as a ceRNA to elevate SPNS2 expression by sponging miR-335–5p

ObjectiveTriple-negative breast cancer (TNBC) is a common cancer with high aggressiveness and high mortality in women. Recently, a plenty of studies have indicated that long non-coding RNAs (lncRNAs) exert the crucial function in human cancers, TNBC is included. The carcinogenicity of lncRNA long intergenic non-protein coding RNA 1503 (LINC01503) has been confirmed in several cancers, nevertheless, its function in TNBC still unclear. Therefore, our study aimed to reveal the underlying mechanism of LINC01503 in TNBC. MethodsIn our study, RT-qPCR was performed to detect the expression of LINC01503 in TNBC cells. The proliferative, invasive, migratory and apoptotic abilities of TNBC cells were detected by functional assay such as CCK-8, clone formation, EdU staining, transwell, and flow cytometry. RIP, RNA pull down, and luciferase assay revealed interactions between LINC01503, miR-335–5p, and sphingolipid transporter protein 2 (SPNS2). Finally, rescue experiments were performed to validate the previous results. ResultsLINC01503 expression was singularly high in TNBC cells. LINC01503 knockdown could restrain cell proliferation, invasion and migration, but accelerated cell apoptosis in TNBC. What’s more, miR-335–5p could be sponged by LINC01503 in TNBC. We also found that overexpressed miR-335–5p could inhibit cell proliferation, migration and invasion and facilitates cell apoptosis. Moreover, SPNS2 was the target gene of miR-335–5p and it functioned as an oncogene in TNBC cells. Finally, we found that overexpressed SPNS2 or inhibited miR-335–5p could reverse the suppressive function of silencing LINC01503 on TNBC progression. ConclusionLINC01503 could facilitate cell proliferation, migration and invasion of TNBC by sponging miR-335–5p to elevate SPNS2 expression.

LPG 18:0 is a general biomarker of asthma and inhibits the differentiation and function of regulatory T cells.

The diagnosis, severity assessment, and development of therapeutic strategies for asthma are crucial aspects of disease management. Since biomarkers are reliable tools in disease management, we aimed to identify and explore asthma-associated biomarkers and investigate their mechanisms. Lipidomics was used to profile serum glycerophospholipids in asthmatic patients and controls. The absolute concentration of lysophosphatidylglycerol (LPG) 18:0 was quantified in various asthma subtypes. Mouse asthma models were used to confirm its potential as a biomarker and investigate its mechanisms in vivo. The effects of LPG 18:0 on CD4+ T cell differentiation, proliferation, and apoptosis were assessed in vitro by flow cytometry, while mitochondrial dysfunction was evaluated through mitochondrial membrane potential, reactive oxygen species, and ATP production measurements. The intracellular mechanism of LPG 18:0 in Tregs was investigated using small molecule inhibitors. The serum glycerophospholipid profile varied between asthmatic patients and control group, with LPG 18:0 levels being notably higher in asthmatic patients, correlating with asthma severity and control level. In vivo and in vitro studies revealed that LPG18:0 impaired naïve CD4+ T cell differentiation into Tregs and compromised their suppressive function. Further investigation demonstrated that LPG18:0 treatment reduced the FOXP3 protein level via SIRT1-mediated deacetylation during Treg differentiation. This study identifies that serum levels of LPG 18:0 are generally elevated in asthmatics and serve as a biomarker for asthma. LPG 18:0 impairs Treg function via the NAD+/SIRT1/FOXP3 pathway. Our research reveals the potential of LPG18:0 as a biomarker for asthma, elucidating its role in asthma diagnosis and treatment.

Mutations in the WG and GW motifs of the three RNA silencing suppressors of grapevine fanleaf virus alter their systemic suppression ability and affect virus infectivity.

Viral suppressors of RNA silencing (VSRs) encoded by grapevine fanleaf virus (GFLV), one of the most economically consequential viruses of grapevine (Vitis spp.), were recently identified. GFLV VSRs include the RNA1-encoded protein 1A and the putative helicase protein 1BHel, as well as their fused form (1ABHel). Key characteristics underlying the suppression function of the GFLV VSRs are unknown. In this study, we explored the role of the conserved tryptophan-glycine (WG) motif in protein 1A and glycine-tryptophan (GW) motif in protein 1BHel in their systemic RNA silencing suppression ability by co-infiltrating Nicotiana benthamiana 16c line plants with a GFP silencing construct and a wildtype or a mutant GFLV VSR. We analyzed and compared wildtype and mutant GFLV VSRs for their (i) efficiency at suppressing RNA silencing, (ii) ability to limit siRNA accumulation, (iii) modulation of the expression of six host genes involved in RNA silencing, (iv) impact on virus infectivity in planta, and (v) variations in predicted protein structures using molecular and biochemical assays, as well as bioinformatics tools such as AlphaFold2. Mutating W to alanine (A) in WG of proteins 1A and 1ABHel abolished their ability to induce systemic RNA silencing suppression, limit siRNA accumulation, and downregulate NbAGO2 expression by 1ABHel. This mutation in the GFLV genome resulted in a non-infectious virus. Mutating W to A in GW of proteins 1BHel and 1ABHel reduced their ability to suppress systemic RNA silencing and abolished the downregulation of NbDCL2, NbDCL4,, and NbRDR6 expression by 1BHel. This mutation in the GFLV genome delayed infection at the local level and inhibited systemic infection in planta. Double mutations of W to A in WG and GW of protein 1ABHel abolished its ability to induce RNA silencing suppression, limit siRNA accumulation, and downregulate NbDCL2 and NbRDR6 expression. Finally, in silico protein structure prediction indicated that a W to A substitution potentially modifies the structure and physicochemical properties of the three GFLV VSRs. Together, this study provided insights into the specific roles of WG/GW not only in GFLV VSR functions but also in GFLV biology.

Vps34 sustains Treg cell survival and function via regulating intracellular redox homeostasis.

The survival and suppressive function of regulatory T (Treg) cells rely on various intracellular metabolic and physiological processes. Our study demonstrates that Vps34 plays a critical role in maintaining Treg cell homeostasis and function by regulating cellular metabolic activities. Disruption of Vps34 in Treg cells leads to spontaneous fatal systemic autoimmune disorder and multi-tissue inflammatory damage, accompanied by a reduction in the number of Treg cells, particularly eTreg cells with highly immunosuppressive activity. Mechanistically, the poor survival of Vps34-deficient Treg cells is attributed to impaired endocytosis, intracellular vesicular trafficking and autophagosome formation, which further results in enhanced mitochondrial respiration and excessive ROS production. Removal of excessive ROS can effectively rescue the death of Vps34-deficient Treg cells. Functionally, acute deletion of Vps34 within established Treg cells enhances anti-tumor immunity in a malignant melanoma model by boosting T-cell-mediated anti-tumor activity. Overall, our results underscore the pivotal role played by Vps34 in orchestrating Treg cell homeostasis and function towards establishing immune homeostasis and tolerance.

Neurotrophic factor Neuritin modulates T cell electrical and metabolic state for the balance of tolerance and immunity.

The adaptive T cell response is accompanied by continuous rewiring of the T cell's electric and metabolic state. Ion channels and nutrient transporters integrate bioelectric and biochemical signals from the environment, setting cellular electric and metabolic states. Divergent electric and metabolic states contribute to T cell immunity or tolerance. Here, we report that neuritin (Nrn1) contributes to tolerance development by modulating regulatory and effector T cell function. Nrn1 expression in regulatory T cells promotes its expansion and suppression function, while expression in the T effector cell dampens its inflammatory response. Nrn1 deficiency causes dysregulation of ion channel and nutrient transporter expression in Treg and effector T cells, resulting in divergent metabolic outcomes and impacting autoimmune disease progression and recovery. These findings identify a novel immune function of the neurotrophic factor Nrn1 in regulating the T cell metabolic state in a cell context-dependent manner and modulating the outcome of an immune response.

Transcription factor Ikzf1 associates with Foxp3 to repress gene expression in Treg cells and limit autoimmunity and anti-tumor immunity

The master transcription factor of regulatory T (Treg) cells, forkhead box protein P3 (Foxp3), controls Treg cell function by targeting certain genes for activation or repression, but the specific mechanisms by which it mediates this activation or repression under different conditions remain unclear. We found that Ikzf1 associates with Foxp3 via its exon 5 (IkE5) and that IkE5-deficient Treg cells highly expressed genes that would otherwise be repressed by Foxp3 upon Tcell receptor stimulation, including Ifng. Treg-specific IkE5-deletion caused interferon-γ (IFN-γ) overproduction, which destabilized Foxp3 expression and impaired Treg suppressive function, leading to systemic autoimmune disease and strong anti-tumor immunity. Pomalidomide, which degrades IKZF1 and IKZF3, induced IFN-γ overproduction in human Treg cells. Mechanistically, the Foxp3-Ikzf1-Ikzf3 complex competed with epigenetic co-activators, such as p300, for binding to target gene loci via chromatin remodeling. Therefore, the Ikzf1 association with Foxp3 is essential for the gene-repressive function of Foxp3 and could be exploited to treat autoimmune disease and cancer.

Stress pathway outputs are encoded by pH-dependent clustering of kinase components

Signal processing by intracellular kinases controls near all biological processes but how signal pathway functions evolve with changed cellular context is poorly understood. Functional specificity of c-Jun N-terminal Kinases (JNK) are partly encoded by signal strength. Here we reveal that intracellular pH (pHi) is a significant component of the JNK network and defines signal response to specific stimuli. We show pHi regulates JNK activity in response to cell stress, with the relationship between pHi and JNK activity dependent on specific stimuli and upstream kinases activated. Using the optogenetic clustering tag CRY2, we show that an increase in pHi promotes the light-induced phase transition of ASK1 to augment JNK activation. While increased pHi similarly promoted CRY2-tagged JNK2 to form light-induced condensates, this attenuated JNK activity. Mathematical modelling of feedback signalling incorporating pHi and differential contributions by ASK1 and JNK2 condensates was sufficient to delineate signal responses to specific stimuli. Taking pHi and ASK1/JNK2 signal contributions into consideration may delineate oncogenic versus tumour suppressive JNK functions and cancer cell drug responses.

Curcumin Inhibits the Development of Pancreatic Cancer by Targeting the circ_0079440/miR-522-3p/EIF4A1 Pathway.

Pancreatic cancer (PC) is a common gastrointestinal cancer with high invasiveness and high mortality. Curcumin is a natural polyphenol with anti-tumor activity against different cancers, including PC. Curcumin has been verified to mediate the expression of circular RNAs (circRNAs) to inhibit tumor development. This study aimed to explore the function and regulatory mechanism of curcumin on circ_0079440 in PC. PC cells were treated with different concentrations of curcumin (0, 5, 10 or 15 μM) for 24 h. Gene expression in PC cells and tissues was detected using RT-qPCR. Cell malignant phenotypes were determined by functional assays. The levels of EMT-related proteins were tested using western blot. RNA interaction was determined using RNA pulldown assay, luciferase reporter assay and RIP assay. The results showed that curcumin suppressed cell proliferative, migratory, and invasive capabilities, and weakened epithelial-mesenchymal transition (EMT) in a concentration-dependent way. Circ_0079440 was expressed at a high level in PC and its level was reduced via curcumin administration in PC cells. Rescue assays showed that circ_0079440 overexpression reversed the suppressive effects of curcumin on PC cell malignant phenotypes. Furthermore, in the xenograft mouse models, curcumin treatment inhibited tumor growth and metastasis, and circ_0079440 upregulation reversed the function of curcumin. Additionally, circ_0079440 was revealed to bind to miR-522-3p to upregulate eukaryotic initiation factor 4A1 (EIF4A1) expression in PC cells. EIF4A1 expression was also downregulated by curcumin, and EIF4A1 overexpression abolished the suppressive functions of curcumin. Moreover, EIF4A overexpression or miR-522-3p inhibition counteracted the anti-tumor effects of circ_0079440 depletion on PC development. To sum up, curcumin suppresses PC development by targeting the circ_0079440/miR-522-3p/EIF4A1 pathway, which might provide novel therapeutic targets for treatment of PC.

Mechanisms of age-related Treg dysfunction in an arthritic environment

Rheumatoid arthritis (RA) is an autoimmune disease characterized by a polyarticular synovitis. In recent years, elderly onset rheumatoid arthritis (EORA) has been increasing. Treg cells in RA have been reported to be dysfunctional, but the relationship between aging and their functional changes is unclear. Here, we found that Treg cells from EORA patients had increased percentages, but decreased activity compared to those from younger onset RA (YORA) patients. In experiments using arthritis model mice, decreased suppressive function and oxygen consumption rate (OCR) were observed in Treg cells only from old arthritic mice. Furthermore, type I interferon (IFN) signaling was upregulated in Treg cells from old GIA mice, and IFN-β decreased the suppressive function of Treg cells. Our findings demonstrate that increased type I IFN signaling in old Treg cells is induced only in the arthritic environment and relates to decreased suppressive function of Treg cells, gets involved in EORA.

Treating activated regulatory T cells with pramipexole protects human dopaminergic neurons from 6-OHDA-induced degeneration.

Parkinson's disease (PD) is a chronic neurodegenerative disorder characterized by the loss of dopaminergic neurons in the substantia nigra, which promotes a sustained inflammatory environment in the central nervous system. Regulatory T cells (Tregs) play an important role in the control of inflammation and might play a neuroprotective role. Indeed, a decrease in Treg number and function has been reported in PD. In this context, pramipexole, a dopaminergic receptor agonist used to treat PD symptoms, has been shown to increase peripheral levels of Treg cells and improve their suppressive function. The aim of this work was to determine the effect of pramipexole on immunoregulatory Treg cells and its possible neuroprotective effect on human dopaminergic neurons differentiated from human embryonic stem cells. Treg cells were sorted from white blood cells of healthy human donors. Assays were performed with CD3/CD28-activated and non-activated Treg cells treated with pramipexole at concentrations of 2 or 200 ng/mL. These regulatory cells were co-cultured with invitro-differentiated human dopaminergic neurons in a cytotoxicity assay with 6-hydroxydopamine (6-OHDA). The role of interleukin-10 (IL-10) was investigated by co-culturing activated IL-10-producing Treg cells with neurons. To further investigate the effect of treatment on Tregs, gene expression in pramipexole-treated, CD3/CD28-activated Treg cells was determined by Fluidigm analysis. Pramipexole-treated CD3/CD28-activated Treg cells showed significant protective effects on dopaminergic neurons when challenged with 6-OHDA. Pramipexole-treated activated Treg cells showed neuroprotective capacity through mechanisms involving IL-10 release and the activation of genes associated with regulation and neuroprotection. Anti-CD3/CD28-activated Treg cells protect dopaminergic neurons against 6-OHDA-induced damage. In addition, activated, IL-10-producing, pramipexole-treated Tregs also induced a neuroprotective effect, and the supernatants of these co-cultures promoted axonal growth. Pramipexole-treated, activated Tregs altered their gene expression in a concentration-dependent manner, and enhanced TGFβ-related dopamine receptor regulation and immune-related pathways. These findings open new perspectives for the development of immunomodulatory therapies for the treatment of PD.

Impact of protein and small molecule interactions on kinase conformations.

Protein kinases act as central molecular switches in the control of cellular functions. Alterations in the regulation and function of protein kinases may provoke diseases including cancer. In this study we investigate the conformational states of such disease-associated kinases using the high sensitivity of the kinase conformation (KinCon) reporter system. We first track BRAF kinase activity conformational changes upon melanoma drug binding. Second, we also use the KinCon reporter technology to examine the impact of regulatory protein interactions on LKB1 kinase tumor suppressor functions. Third, we explore the conformational dynamics of RIP kinases in response to TNF pathway activation and small molecule interactions. Finally, we show that CDK4/6 interactions with regulatory proteins alter conformations which remain unaffected in the presence of clinically applied inhibitors. Apart from its predictive value, the KinCon technology helps to identify cellular factors that impact drug efficacies. The understanding of the structural dynamics of full-length protein kinases when interacting with small molecule inhibitors or regulatory proteins is crucial for designing more effective therapeutic strategies.

Impact of protein and small molecule interactions on kinase conformations

Protein kinases act as central molecular switches in the control of cellular functions. Alterations in the regulation and function of protein kinases may provoke diseases including cancer. In this study we investigate the conformational states of such disease-associated kinases using the high sensitivity of the kinase conformation (KinCon) reporter system. We first track BRAF kinase activity conformational changes upon melanoma drug binding. Second, we also use the KinCon reporter technology to examine the impact of regulatory protein interactions on LKB1 kinase tumor suppressor functions. Third, we explore the conformational dynamics of RIP kinases in response to TNF pathway activation and small molecule interactions. Finally, we show that CDK4/6 interactions with regulatory proteins alter conformations which remain unaffected in the presence of clinically applied inhibitors. Apart from its predictive value, the KinCon technology helps to identify cellular factors that impact drug efficacies. The understanding of the structural dynamics of full-length protein kinases when interacting with small molecule inhibitors or regulatory proteins is crucial for designing more effective therapeutic strategies.

A novel cascaded H-bridge photovoltaic inverter with flexible arc suppression function

This paper presents a novel approach that simultaneously enables photovoltaic (PV) inversion and flexible arc suppression during single-phase grounding faults. Inverters compensate for ground currents through an arc-elimination function, while outputting a PV direct current (DC) power supply. This method effectively reduces the residual grounding current. To reduce the dependence of the arc-suppression performance on accurate compensation current-injection models, an adaptive fuzzy neural network imitating a sliding mode controller was designed. An online adaptive adjustment law for network parameters was developed, based on the Lyapunov stability theorem, to improve the robustness of the inverter to fault and connection locations. Furthermore, a new arc-suppression control exit strategy is proposed to allow a zero- sequence voltage amplitude to quickly and smoothly track a target value by controlling the nonlinear decrease in current and reducing the regulation time. Simulation results showed that the proposed method can effectively achieve fast arc suppression and reduce the fault impact current in single-phase grounding faults. Compared to other methods, the proposed method can generate a lower residual grounding current and maintain good arc-suppression performance under different transition resistances and fault locations.

Characterization of novel CD8+ regulatory T cells and their modulatory effects in murine model of inflammatory bowel disease

Dysregulation of mucosal immune system has been proposed to be critical in the pathogenesis of inflammatory bowel diseases (IBDs). Regulatory T cells (Tregs) play an important role in regulating immune responses. Tregs are involved in maintaining intestinal homeostasis and exerting suppressive function in colitis. Our previous studies showed that a novel forkhead box protein P3 (Foxp3) negative Tregs (Treg-of-B cells), induced by culturing naïve CD4+ T cells with B cells, could protect against colitis and downregulate T helper (Th) 1 and Th17 cell cytokines in T cell-mediated colitis. In the present study, we aimed to induce Treg-of-B cells in the CD8+ T-cell population and investigate their characteristics and immunomodulatory functions. Our results showed that CD8+ Treg-of-B cells expressed Treg-associated markers, including lymphocyte-activation gene-3 (LAG3), inducible co-stimulator (ICOS), programmed death-1 (PD-1), cytotoxic T-lymphocyte-associated protein-4 (CTLA-4), tumor necrosis factor receptor superfamily member-4 (TNFRSF4, OX40), and tumor necrosis factor receptor superfamily member-18 (TNFRSF18, GITR), but did not express Foxp3. CD8+ Treg-of-B cells produced higher concentration of inhibitory cytokine interleukin (IL)-10, and expressed higher levels of cytotoxic factor granzyme B and perforin after stimulation, compared to those of CD8+CD25- T cells. Moreover, CD8+ Treg-of-B cells suppressed T cell proliferation in vitro and alleviated colonic inflammation in chronic dextran sulfate sodium (DSS)-induced colitis. In conclusion, our study identified a novel subpopulation of CD8+ Tregs with suppressive effects through cell contact. These CD8+ Treg-of-B cells might have therapeutic potential for IBDs.

Human gut microbiota-reactive DP8α Tregs prevent acute graft-versus-host disease in a CD73-dependent manner.

Graft-versus-host disease (GvHD) is a life-threatening complication frequently occurring following allogeneic hematopoietic stem cell transplantation (allo-HSCT). Since gut microbiota and regulatory T cells (Tregs) are believed to play roles in GvHD prevention, we investigated whether DP8α Tregs, which we have previously described to harbor a T cell receptor specificity for the gut commensal Faecalibacterium prausnitzii, could protect against GvHD, thereby linking the microbiota and its effect on GvHD. We observed a decrease in CD73+ DP8α Treg frequency in allo-HSCT patients 1 month after transplantation, which was associated with acute GvHD (aGvHD) development at 1 month after transplantation, as compared with aGvHD-free patients, without being correlated to hematological disease relapse. Importantly, CD73 activity was shown to be critical for DP8α Treg suppressive function. Moreover, the frequency of host-reactive DP8α Tregs was also lower in aGvHD patients, as compared with aGvHD-free patients, which could embody a protective mechanism responsible for the maintenance of this cell subset in GvHD-free patients. We also showed that human DP8α Tregs protected mice against xenogeneic GvHD through limiting deleterious inflammation and preserving gut integrity. Altogether, these results demonstrated that human DP8α Tregs mediate aGvHD prevention in a CD73-dependent manner, likely through host reactivity, advocating for the use of these cells for the development of innovative therapeutic strategies to preclude aGvHD-related inflammation.