Reduced CD4+,CD25- T cell sensitivity to the suppressive function of CD4+,CD25high,CD127 -/low regulatory T cells in patients with active systemic lupus erythematosus

Antigen-specific immunotherapies for autoimmune disease

Antigen-specific therapies have a long history in the treatment of allergy but have not been successful in autoimmunity. However, in the past 20 years, advances in the definition of the self-antigens that promote autoimmunity and the growing understanding of the mechanisms that maintain tolerance in health but fail in autoimmunity have led to antigen-specific approaches being considered for the treatment of autoimmune diseases. The core goal of each antigen-specific treatment approach is to remove the immune response that promotes autoimmunity whilst sparing protective responses. Approaches to antigen-specific therapy range from targeted deletion of autoreactive lymphocytes to tolerization of autoreactive T cells and active inhibition of autoimmune responses. Technologies such as vaccines, nanoparticles, cell-based therapies and gene editing are being harnessed to achieve these goals. Remaining challenges include the selection of the best antigen to target, modality and timing of administration of these therapies and the disease in which the therapies are used; overcoming these challenges will be vital to move antigen-specific therapies forward. Once established, antigen-specific therapy has the potential to be applied broadly in the area of autoimmunity.

Defining Human Regulatory T Cells beyond FOXP3: The Need to Combine Phenotype with Function

Regulatory T cells (Tregs) are essential to maintain immune homeostasis by promoting self-tolerance. Reduced Treg numbers or functionality can lead to a loss of tolerance, increasing the risk of developing autoimmune diseases. An overwhelming variety of human Tregs has been described, based on either specific phenotype, tissue compartment, or pathological condition, yet the bulk of the literature only addresses CD25-positive and CD127-negative cells, coined by naturally occurring Tregs (nTregs), most of which express the transcription factor Forkhead box protein 3 (FOXP3). While the discovery of FOXP3 was seminal to understanding the origin and biology of nTregs, there is evidence in humans that not all T cells expressing FOXP3 are regulatory, and that not all Tregs express FOXP3. Namely, the activation of human T cells induces the transient expression of FOXP3, irrespective of whether they are regulatory or inflammatory effectors, while some induced T cells that may be broadly defined as Tregs (e.g., Tr1 cells) typically lack demethylation and do not express FOXP3. Furthermore, it is unknown whether and how many nTregs exist without FOXP3 expression. Several other candidate regulatory molecules, such as GITR, Lag-3, GARP, GPA33, Helios, and Neuropilin, have been identified but subsequently discarded as Treg-specific markers. Multiparametric analyses have uncovered a plethora of Treg phenotypes, and neither single markers nor combinations thereof can define all and only Tregs. To date, only the functional capacity to inhibit immune responses defines a Treg and distinguishes Tregs from inflammatory T cells (Teffs) in humans. This review revisits current knowledge of the Treg universe with respect to their heterogeneity in phenotype and function. We propose that it is unavoidable to characterize human Tregs by their phenotype in combination with their function, since phenotype alone does not unambiguously define Tregs. There is an unmet need to align the expression of specific markers or combinations thereof with a particular suppressive function to coin functional Treg entities and categorize Treg diversity.

Sex-specific differences in ICOS+ T helper cell differentiation in systemic lupus erythematosus patients with low disease activity

Systemic lupus erythematosus (SLE) is a sex biased chronic autoimmune disease affecting predominantly females during reproductive ages. Changes in the ratio of inducible costimulatory molecule (ICOS)+ regulatory (Treg) and non-regulatory responder (Tresp) CD4+ T cells proved to be crucial for the occurrence of high disease activity. Here, we investigated how the differentiation of ICOS+CD45RA+CD31+ recent thymic emigrant (RTE) Tresps into CD45RA-CD31- memory Tresps affects the percentages of ICOS+ Tresps within total CD4+ T cells. Three different pathways (pathway 1 via CD45RA-CD31+ memory Tresps, pathway 2 via direct proliferation and pathway 3 via resting mature naïve CD45RA+CD31- (MN) cells) were examined in healthy controls and SLE remission patients separated by sex. In female SLE remission patients, immunosuppressive therapy inhibited the ICOS+ RTE differentiation via CD45RA-CD31+ memory Tresps and direct proliferation, leaving an age-independently increased differentiation into CD45RA-CD31- memory Tresps by conversion of resting MN Tresps compared with healthy controls. Due to exhaustion of this pathway with age, no age-dependent change in the percentages of ICOS+ Tresps within total CD4+ T cells could be found. In contrast, no age-independently increased differentiation could be detected in men due to sufficient immunosuppression of all three pathways. This allowed an age-dependent differentiation of ICOS+ RTE Tresps into CD45RA-CD31- memory Tresps by conversion of resting MN Tresps, resulting in age-dependently increasing percentages of ICOS+ Tresps within total CD4+ T cells. We hypothesize that the sex-specific differential effect of immunosuppression on the differentiation of ICOS+ Tresps may explain the sex- and age-dependent occurrence of high disease activity.

Helios as a Potential Biomarker in Systemic Lupus Erythematosus and New Therapies Based on Immunosuppressive Cells

The Helios protein (encoded by the IKZF2 gene) is a member of the Ikaros transcription family and it has recently been proposed as a promising biomarker for systemic lupus erythematosus (SLE) disease progression in both mouse models and patients. Helios is beginning to be studied extensively for its influence on the T regulatory (Treg) compartment, both CD4+ Tregs and KIR+/Ly49+ CD8+ Tregs, with alterations to the number and function of these cells correlated to the autoimmune phenomenon. This review analyzes the most recent research on Helios expression in relation to the main immune cell populations and its role in SLE immune homeostasis, specifically focusing on the interaction between T cells and tolerogenic dendritic cells (tolDCs). This information could be potentially useful in the design of new therapies, with a particular focus on transfer therapies using immunosuppressive cells. Finally, we will discuss the possibility of using nanotechnology for magnetic targeting to overcome some of the obstacles related to these therapeutic approaches.

Allogeneic cord blood regulatory T cells decrease dsDNA antibody and improve albuminuria in systemic lupus erythematosus

Background

Lupus nephritis (LN) constitutes the most severe organ manifestations of systemic lupus erythematosus (SLE), where pathogenic T cells have been identified to play an essential role in 'helping' B cells to make autoantibodies and produce inflammatory cytokines that drive kidney injury in SLE. Regulatory T cells (Tregs), responsible for decreasing inflammation, are defective and decreased in SLE and have been associated with disease progression. We hypothesize that treatment with allogeneic, healthy Tregs derived from umbilical cord blood (UCB) may arrest such an inflammatory process and protect against kidney damage.

Methods

UCB-Tregs function was examined by their ability to suppress CellTrace Violet-labeled SLE peripheral blood mononuclear cells (PBMCs) or healthy donor (HD) conventional T cells (Tcons); and by inhibiting secretion of inflammatory cytokines by SLE PBMCs. Humanized SLE model was established where female Rag2-/-γc-/- mice were transplanted with 3 × 106 human SLE-PBMCs by intravenous injection on day 0, followed by single or multiple injection of UCB-Tregs to understand their impact on disease development. Mice PB was assessed weekly by flow cytometry. Phenotypic analysis of isolated cells from mouse PB, lung, spleen, liver and kidney was performed by flow cytometry. Kidney damage was assessed by quantifying urinary albumin and creatinine secretion. Systemic disease was evaluated by anti-dsDNA IgG Ab analysis as well as immunohistochemistry analysis of organs. Systemic inflammation was determined by measuring cytokine levels.

Results

In vitro, UCB-Tregs are able to suppress HD Tcons and pathogenic SLE-PBMCs to a similar extent. UCB-Tregs decrease secretion of several inflammatory cytokines including IFN-γ, IP-10, TNF-α, IL-6, IL-17A, and sCD40L by SLE PBMCs in a time-dependent manner, with a corresponding increase in secretion of suppressor cytokine, IL-10. In vivo, single or multiple doses of UCB-Tregs led to a decrease in CD8+ T effector cells in different organs and a decrease in circulating inflammatory cytokines. Improvement in skin inflammation and loss of hair; and resolution of CD3+, CD8+, CD20+ and Ki67+ SLE-PBMC infiltration was observed in UCB-Treg recipients with a corresponding decrease in plasma anti-double stranded DNA IgG antibody levels and improved albuminuria.

Conclusions

UCB-Tregs can decrease inflammatory burden in SLE, reduce auto-antibody production and resolve end organ damage especially, improve kidney function. Adoptive therapy with UCB-Tregs should be explored for treatment of lupus nephritis in the clinical setting.

Innate and adaptive immune abnormalities underlying autoimmune diseases: the genetic connections

With the exception of an extremely small number of cases caused by single gene mutations, most autoimmune diseases result from the complex interplay between environmental and genetic factors. In a nutshell, etiology of the common autoimmune disorders is unknown in spite of progress elucidating certain effector cells and molecules responsible for pathologies associated with inflammatory and tissue damage. In recent years, population genetics approaches have greatly enriched our knowledge regarding genetic susceptibility of autoimmunity, providing us with a window of opportunities to comprehensively re-examine autoimmunity-associated genes and possible pathways. In this review, we aim to discuss etiology and pathogenesis of common autoimmune disorders from the perspective of human genetics. An overview of the genetic basis of autoimmunity is followed by 3 chapters detailing susceptibility genes involved in innate immunity, adaptive immunity and inflammatory cell death processes respectively. With such attempts, we hope to expand the scope of thinking and bring attention to lesser appreciated molecules and pathways as important contributors of autoimmunity beyond the 'usual suspects' of a limited subset of validated therapeutic targets.

Phosphofructokinase P fine-tunes T regulatory cell metabolism, function, and stability in systemic autoimmunity

Systemic lupus erythematosus (SLE) is an autoimmune disease characterized by defective regulatory T (Treg) cells. Here, we demonstrate that a T cell-specific deletion of calcium/calmodulin-dependent protein kinase 4 (CaMK4) improves disease in B6.lpr lupus-prone mice and expands Treg cells. Mechanistically, CaMK4 phosphorylates the glycolysis rate-limiting enzyme 6-phosphofructokinase, platelet type (PFKP) and promotes aerobic glycolysis, while its end product fructose-1,6-biphosphate suppresses oxidative metabolism. In Treg cells, a CRISPR-Cas9-enabled Pfkp deletion recapitulated the metabolism of Camk4-/- Treg cells and improved their function and stability in vitro and in vivo. In SLE CD4+ T cells, PFKP enzymatic activity correlated with SLE disease activity and pharmacologic inhibition of CaMK4-normalized PFKP activity, leading to enhanced Treg cell function. In conclusion, we provide molecular insights in the defective metabolism and function of Treg cells in SLE and identify PFKP as a target to fine-tune Treg cell metabolism and thereby restore their function.

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.

Restoration of Follicular T Regulatory/Helper Cell Balance by OX40L-JAG1 Cotreatment Suppresses Lupus Nephritis in NZBWF1/j Mice

Class-switched antinuclear autoantibodies produced by T follicular helper (TFH) cell-dependent germinal center (GC) B cell response play an essential pathogenic role in lupus nephritis (LN). The role of T follicular regulatory (TFR) cells, an effector subset of CD4⁺Foxp3⁺ T regulatory cells (Tregs), which are specialized in suppressing TFH-GC response and Ab production, remains elusive in LN. Contrasting reports have shown increased/reduced circulating TFR cells in human lupus that might not accurately reflect their presence in the GCs of relevant lymphoid organs. In this study, we report a progressive reduction in TFR cells and decreased TFR/TFH ratio despite increased Tregs in the renal lymph nodes of NZBWF1/j mice, which correlated with increased GC-B cells and proteinuria onset. Cotreatment with soluble OX40L and Jagged-1 (JAG1) proteins increased Tregs, TFR cells, and TFR/TFH ratio, with a concomitant reduction in TFH cells, GC B cells, and anti-dsDNA IgG Ab levels, and suppressed LN onset. Mechanistic studies showed attenuated TFH functions and diminished GC events such as somatic hypermutation and isotype class-switching in OX40L-JAG1-treated mice. RNA sequencing studies revealed inhibition of hypoxia-inducible factor 1-α (HIF-1a) and STAT3 signaling in T conventional cells from OX40L-JAG1-treated mice, which are critical for the glycolytic flux and differentiation into TFH cell lineage. Therefore, the increased TFR/TFH ratio seen in OX40L-JAG1-treated mice could involve both impaired differentiation of TFH cells from T conventional cells and expansion of TFR cells. We show a key role for GC-TFR/TFH imbalance in LN pathogenesis and how restoring homeostatic balance can suppress LN.

Genetic Variations Controlling Regulatory T Cell Development and Activity in Mouse Models of Lupus-Like Autoimmunity

Immune homeostasis is a constant balancing act between effector T cells and regulatory T cells defined by Foxp3 expression, the transcription factor that drives their differentiation and immunosuppressive activity. Immune homeostasis is altered when Treg cells are not generated or maintained in sufficient numbers. Treg cells rendered unstable by loss of Foxp3 expression, known as ex-Treg cells, gain pro-inflammatory functions. Treg cells may also become dysfunctional and lose their suppressive capabilities. These alterations can cause an imbalance between effector and regulatory subsets, which may ultimately lead to autoimmunity. This review discusses recent studies that identified genetic factors that maintain Treg cell stability as well as preserve their suppressive function. We focus on studies associated with systemic lupus erythematosus and highlight their findings in the context of potential therapeutic gene targeting in Treg cells to reverse the phenotypic changes and functional dysregulation inducing autoimmunity.

Lupus Susceptibility Loci Predispose Mice to Clonal Lymphocytic Responses and Myeloid Expansion

Lupus susceptibility results from the combined effects of numerous genetic loci, but the contribution of these loci to disease pathogenesis has been difficult to study due to the large cellular heterogeneity of the autoimmune immune response. We performed single-cell RNA, BCR, and TCR sequencing of splenocytes from mice with multiple polymorphic lupus susceptibility loci. We not only observed lymphocyte and myeloid expansion, but we also characterized changes in subset frequencies and gene expression, such as decreased CD8 and marginal zone B cells and increased Fcrl5- and Cd5l-expressing macrophages. Clonotypic analyses revealed expansion of B and CD4 clones, and TCR repertoires from lupus-prone mice were distinguishable by algorithmic specificity prediction and unsupervised machine learning classification. Myeloid differential gene expression, metabolism, and altered ligand-receptor interaction were associated with decreased Ag presentation. This dataset provides novel mechanistic insight into the pathophysiology of a spontaneous model of lupus, highlighting potential therapeutic targets for autoantibody-mediated disease.

Cardiovascular disease risk and pathogenesis in systemic lupus erythematosus

Systemic lupus erythematosus (SLE) often features extensive cardiovascular (CV) comorbidity and patients with SLE are at significantly increased risk of CV event occurrence and CV-related mortality. While the specific mechanisms leading to this increased cardiovascular disease (CVD) risk remain to be fully characterized, this heightened risk cannot be fully explained by traditional CV risk factors and is likely driven by immunologic and inflammatory features of SLE. Widespread innate and adaptive immune dysregulation characterize SLE, and factors including excessive type I interferon burden, inappropriate formation and ineffective clearance of neutrophil extracellular traps, and autoantibody formation have been linked to clinical and metabolic features impacting CV risk in SLE and may represent pathogenic drivers of SLE-related CVD. Indeed, functional and phenotypic aberrations in almost every immune cell type are present in SLE and may impact CVD progression. As understanding of the contribution of SLE-specific factors to CVD in SLE improves, improved screening and monitoring of CV risk alongside development of therapeutic treatments aimed at prevention of CVD in SLE patients are required and remain the focus of several ongoing studies and lines of inquiry.

Cardiovascular disease risk and pathogenesis in systemic lupus erythematosus

Systemic lupus erythematosus (SLE) often features extensive cardiovascular (CV) comorbidity and patients with SLE are at significantly increased risk of CV event occurrence and CV-related mortality. While the specific mechanisms leading to this increased cardiovascular disease (CVD) risk remain to be fully characterized, this heightened risk cannot be fully explained by traditional CV risk factors and is likely driven by immunologic and inflammatory features of SLE. Widespread innate and adaptive immune dysregulation characterize SLE, and factors including excessive type I interferon burden, inappropriate formation and ineffective clearance of neutrophil extracellular traps, and autoantibody formation have been linked to clinical and metabolic features impacting CV risk in SLE and may represent pathogenic drivers of SLE-related CVD. Indeed, functional and phenotypic aberrations in almost every immune cell type are present in SLE and may impact CVD progression. As understanding of the contribution of SLE-specific factors to CVD in SLE improves, improved screening and monitoring of CV risk alongside development of therapeutic treatments aimed at prevention of CVD in SLE patients are required and remain the focus of several ongoing studies and lines of inquiry.

Regulatory T cell function in autoimmune disease

Autoimmune diseases are characterized by a failure of tolerance to own body components resulting in tissue damage. Regulatory T cells are gatekeepers of tolerance. This review focusses on the function and pathophysiology of regulatory T cells in the context of autoimmune diseases including rheumatoid and juvenile idiopathic arthritis as well as systemic lupus erythematosus with an overview over current and future therapeutic options to boost Treg function.

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Regulatory T cells are critical mediators of immune tolerance and critically depend on external IL-2.

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Tregs are expanded during inflammation, where the local milieu enhances resistance to suppression in T effector cells.

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Human Tregs are characterized by different markers, which hampers the comparability of studies in patients with autoimmunity.

Splicing factor SRSF1 controls distinct molecular programs in regulatory and effector T cells implicated in systemic autoimmune disease

Systemic autoimmune diseases are characterized by hyperactive effector T cells (Teffs), aberrant cytokines and chemokines, and dysfunctional regulatory T cells (Tregs). We previously uncovered new roles for serine/arginine-rich splicing factor 1 (SRSF1) in the control of genes involved in T cell signaling and cytokine production in human T cells. SRSF1 levels are decreased in T cells from patients with systemic lupus erythematosus (SLE), and low levels correlate with severe disease. Moreover, T cell-conditional Srsf1-deficient mice recapitulate the autoimmune phenotype, exhibiting CD4 T cell hyperactivity, dysfunctional Tregs, systemic autoimmunity, and tissue inflammation. However, the role of SRSF1 in controlling molecular programs in Teffs and Tregs and how these pathways are implicated in autoimmunity is not known. Here, by comparative bioinformatics analysis, we demonstrate that SRSF1 controls largely distinct gene programs in Tregs and Teffs in vivo. SRSF1 regulates 189 differentially expressed genes (DEGs) unique to Tregs, 582 DEGs unique to Teffs, and 29 DEGs shared between both. Shared genes included IL-17A, IL-17F, CSF1, CXCL10, and CXCR4, and were highly enriched for inflammatory response and cytokine-cytokine receptor interaction pathways. SRSF1 controls distinct pathways in Tregs, which include chemokine signaling and immune cell differentiation, compared with pathways in Teffs, which include cytokine production, T cell homeostasis, and activation. We identified putative mRNA binding targets of SRSF1 which include CSF1, CXCL10, and IL-17F. Finally, comparisons with transcriptomics profiles from lupus-prone MRL/lpr mice reveal that SRSF1 controls genes and pathways implicated in autoimmune disease. The target genes of SRSF1 and putative binding targets we discovered, have known roles in systemic autoimmunity. Our findings suggest that SRSF1 controls distinct molecular pathways in Tregs and Teffs and aberrant SRSF1 levels may contribute to their dysfunction and immunopathogenesis of systemic autoimmune disease.

CQMUH-011 mitigates autoimmune hepatitis via inhibiting the function of T lymphocytes

CQMUH-011 is a modified adamantane sulfonamide compound, that inhibits macrophage proliferation and possesses anti-inflammatory properties. Here, fresh mouse splenocytes were obtained and stimulated with concanavalin A (ConA, 5 μg/ml) in vitro; and experimental autoimmune hepatitis (AIH) was induced by ConA (20 mg/kg, iv) in vivo, to clarify the protective effects of CQMUH-011 against AIH and its possible mechanisms. Our results demonstrated that CQMUH-011 pretreatment can dose-dependently inhibit the proliferation of splenocytes in vitro. In vivo, CQMUH-011 administration reduced the hepatic histopathological score and the infiltration of lymphocytes in the liver parenchyma; additionally, it downregulated the levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST) and pro-inflammatory cytokines interferon (IFN)-γ, tumor necrosis factor (TNF)-α, and interleukin (IL)-6 in serum, as well as those of methane dicarboxylic aldehyde and myeloperoxidase in the liver tissues. It also down-regulated the expression of p-NF-κB and related proteins in the liver tissues. Furthermore, CQMUH-011 could maintain the balance of CD3+ CD4+ /CD3+ CD8+ and decrease the percentages of CD8+ CD69+ and CD4+ CD25+/- CD69+ T-cells in the splenocytes of ConA-challenged mice. Moreover, we found thatCD4+ CD25+/- CD69+ T-cells were significantly correlated with ALT levels, especially CD4+ CD25- CD69+ T-cells. In conclusion, CQMUH-011 exerts potential protective effects against ConA-induced hepatitis, which may be partially attributed to its inhibition of T cells, especially the suppression of the proliferation of CD4+ CD25- CD69+ and CD8+ CD69+ subsets in the spleen. CQMUH-011 also reduced the early apoptosis of lymphocytes in the thymus.

Impaired Differentiation of Highly Proliferative ICOS+-Tregs Is Involved in the Transition from Low to High Disease Activity in Systemic Lupus Erythematosus (SLE) Patients

Dysregulations in the differentiation of CD4⁺-regulatory-T-cells (Tregs) and CD4⁺-responder-T-cells (Tresps) are involved in the development of active systemic lupus erythematosus (SLE). Three differentiation pathways of highly proliferative inducible costimulatory molecule (ICOS)⁺- and less proliferative ICOS^--CD45RA⁺CD31⁺-recent-thymic-emigrant (RTE)-Tregs/Tresps via CD45RA^-CD31⁺-memory-Tregs/Tresps (CD31⁺-memory-Tregs/Tresps), their direct proliferation via CD45RA⁺CD31^--mature naïve (MN)-Tregs/Tresps, and the production and differentiation of resting MN-Tregs/Tresp into CD45RA^-CD31^--memory-Tregs/Tresps (CD31^--memory-Tregs/Tresps) were examined in 115 healthy controls, 96 SLE remission patients, and 20 active disease patients using six color flow cytometric analysis. In healthy controls an appropriate sequence of these pathways ensured regular age-dependent differentiation. In SLE patients, an age-independently exaggerated differentiation was observed for all Treg/Tresp subsets, where the increased conversion of resting MN-Tregs/Tresps particularly guaranteed the significantly increased ratios of ICOS⁺-Tregs/ICOS⁺-Tresps and ICOS^--Tregs/ICOS^--Tresps during remission. Changes in the differentiation of resting ICOS⁺-MN-Tresps and ICOS^--MN-Tregs from conversion to proliferation caused a significant shift in the ratio of ICOS⁺-Tregs/ICOS⁺-Tresps in favor of ICOS⁺-Tresps and a further increase in the ratio of ICOS^--Tregs/ICOS^--Tresps with active disease. The differentiation of ICOS⁺-RTE-Tregs/Tresps seems to be crucial for keeping patients in remission, where their limited production of proliferating resting MN-Tregs may be responsible for the occurrence of active disease flares.

Reactive oxygen species: The Yin and Yang in (auto-)immunity

Reactive oxygen species (ROS) are produced by immune cells in response to antigens. They are produced mostly in the mitochondria and their levels are tightly controlled by a series of metabolic processes. ROS are necessary for the development of the immune response but the role of ROS in the development of autoimmune disease needs further clarification. Early clinical information points to the beneficial role of supplementation of antioxidant agents or the reduction of ROS production. We review recent information in the field in an effort to identify areas more studies are needed.

T Cell Abnormalities in the Pathogenesis of Systemic Lupus Erythematosus: an Update

PURPOSE OF REVIEW

Systemic lupus erythematosus is a complex disease with broad spectrum of clinical manifestations. In addition to abnormal B cell responsive leading to autoantibody production, various T cells also play different roles in promoting systemic autoimmunity and end organ damage. We aim to provide a review on recent developments in how abnormalities in different T cells subsets contribute to systemic lupus erythematosus pathogenesis and how they inform the consideration of new promising therapeutics.

RECENT FINDINGS

Distinct subsets of T cells known as T follicular helper cells enable the production of pathogenic autoantibodies. Detailed understanding of the B cell helping T cell subsets should improve the performance of clinical trials targeting the cognate T:B cell interaction. CD8⁺ T cells play a role in peripheral tolerance and reversal of its exhausted phenotype could potentially alleviate both systemic autoimmunity and the risk of infection. Research on the abnormal lupus T cell signaling also leads to putative therapeutic targets able to restore interleukin-2 production and suppress the production of the pathogenic IL-17 cytokine. Recently, several studies have focused on dissecting T cell populations located in the damaged organs, aiming to target the pathogenic processes specific to each organ. Numerous T cell subsets play distinct roles in SLE pathogenesis and recent research in understanding abnormal signaling pathways, cellular metabolism, and environmental cues pave the way for the development of novel therapeutics.

Paeoniflorin ameliorates murine lupus nephritis by increasing CD4+Foxp3+ Treg cells via enhancing mTNFα-TNFR2 pathway

Treg cells are essential for re-establishing self-tolerance in lupus. However, given that direct Treg therapies may be inadequate to control autoimmunity and inflammation, a strategy of inducing or expanding endogenous Treg cells in vivo may be a good option. Macrophages are main tissue-infiltrating cells and play a role in promoting Treg differentiation while paeoniflorin (PF), a monoterpene glycoside, exhibits anti-inflammatory and immunoregulatory effects. Here, we studied the effects of PF on CD4⁺FoxP3⁺ Treg frequency and the potential mechanisms involving M2 macrophages. We demonstrated that PF ameliorated lupus nephritis in lupus-prone B6/gld mice by reducing urinary protein, serum creatinine and anti-dsDNA levels, diminishing renal cellular infiltration, improving renal immunopathology and downregulating renal gene and protein expressions of key cytokines, including IFN-γ, IL-6, IL-12 and IL-23. PF also lowered the percentage of CD44^highCD62L^low effector T cells while augmenting CD4⁺FoxP3⁺ Treg frequency in B6/gld mice. Importantly, PF increased TNFR2 expression on CD4⁺FoxP3⁺ Tregs, but not CD4⁺FoxP3^- T cells, in vivo and in vitro. Furthermore, we found that CD206⁺ subset of F4/80⁺CD11b⁺ macrophages expressed a higher level of mTNF-α than their CD206^- counterparts while PF increased mTNF-α expression on CD206⁺ macrophages in vitro and in vivo. In vitro studies showed that mTNF-α⁺ M2 macrophages were more potent in inducing Treg differentiation and proliferation than their mTNF-α^- counterparts, whereas the effects of mTNF-α⁺ M2 macrophages were largely reversed by separation of M2 macrophages using a transwell or TNFR2-blocking Ab in the culture. Finally, PF also promoted in vitro Treg generation induced by M2 macrophages. Thus, we demonstrated that mTNFα-TNFR2 interaction is a new mechanism responsible for Treg differentiation mediated by M2 macrophages. We provided the first evidence that PF may be used to treat lupus nephritis.

Emerging patterns of regulatory T cell function in tuberculosis

Tuberculosis (TB) is one of the top 10 causes of mortality worldwide from a single infectious agent and has significant implications for global health. A major hurdle in the development of effective TB vaccines and therapies is the absence of defined immune‐correlates of protection. In this context, the role of regulatory T cells (T_reg), which are essential for maintaining immune homeostasis, is even less understood. This review aims to address this knowledge gap by providing an overview of the emerging patterns of T_reg function in TB. Increasing evidence from studies, both in animal models of infection and TB patients, points to the fact the role of T_regs in TB is dependent on disease stage. While T_regs might expand and delay the appearance of protective responses in the early stages of infection, their role in the chronic phase perhaps is to counter‐regulate excessive inflammation. New data highlight that this important homeostatic role of T_regs in the chronic phase of TB may be compromised by the expansion of activated human leucocyte antigen D‐related (HLA‐DR)⁺CD4⁺ suppression‐resistant effector T cells. This review provides a comprehensive and critical analysis of the key features of T_reg cells in TB; highlights the importance of a balanced immune response as being important in TB and discusses the importance of probing not just T_reg frequency but also qualitative aspects of T_reg function as part of a comprehensive search for novel TB treatments.

Reduced activated regulatory T cells and imbalance of Th17/activated Treg cells marks renal involvement in ANCA-associated vasculitis

The role of naturally occurring regulatory T cells (Treg) in the control of the immune tolerance of ANCA-associated vasculitis (AAV) has not been well defined. Therefore, we separate the phenotypically heterogeneous Treg cells into different subsets based on the expression of FOXP3 and CD45RA during AAV pathogenesis. Fifty-four AAV patients (38 patients with renal involvement) and 19 healthy controls (HCs) were enrolled in this study. Levels of CD4⁺T cell subsets and cytokines were detected by flow cytometry. Treg immunesuppression capacity was measured in co-culture experiments. The diagnostic value for Treg subsets was evaluated by the areas under the receiver operating characteristic curves (AUC). Patients with AAV had lower percentages and numbers of activated Treg cells (aTreg, P = 0.044, P = 0.002), while higher levels of total Treg cells (P = 0.001, P = 0.026) with diminished immunosuppression capacity. The proportions of effector memory T-cell subpopulation (P < 0.001) were increased in AAV patients. Interestingly, the AUC of the aTreg improved significantly the diagnostic potential of AAV. Furthermore, the ratio of Th17/aTreg was significantly increased in active and renal vasculitis patient and positive correlation between Th17/Treg subset ratio and creatinine or BUN. In addition, we found that cytokine IL-2 and IL-4 exhibited a downward while IL-6, IL-10, TNF-α, IFN-γ and IL-17A trend upward in AAV patients. Increase in total Treg levels, along with functional deficiency, and decrease in aTreg cells constitute potential novel biomarkers for AAV. And the ratio of Th17/aTreg might serve as an important tool to recognize and monitor AAV patients with renal involvement and disease remission.

Treg cells in health and autoimmune diseases: New insights from single cell analysis

Autoimmune diseases, such as Systemic Lupus Erythematosus (SLE) or Rheumatoid Arthritis (RA) are characterized by the breakdown of immunological tolerance. Defects of regulatory T cells have been described among the various mechanisms, that are important for the development of autoimmune diseases, due to their critical role as regulators of peripheral immune tolerance and homeostasis. Initially T suppressor cells have been described as one population of peripheral T cells. Based on new technological advances a new understanding of the heterogeneity of different Treg cell populations in the lymphoid and non-lymphoid tissue has evolved over the last years. While initially Foxp3 has been defined as the main master regulator of Treg cells, we have learned that Treg cells from various tissue can be identified by a specific transcriptomic and epigenetic signature. Epigenetic mechanisms allow Treg cell stability, but we have also learned that certain Treg subsets are plastic and can under specific circumstances even enhance autoimmunity and inflammatory processes. Quantitative and functional defects of Treg cells have been observed in a variety of autoimmune diseases. Due to our understanding of the nature of this cell population, Treg cells have been a target of new Treg based therapies, such as low-dose IL-2. In addition, ongoing clinical trials aim to test safety and efficacy of transferred, in vitro expanded Treg cells in patients with autoimmune diseases and transplant patients.

Trisomy 21 dysregulates T cell lineages toward an autoimmunity-prone state associated with interferon hyperactivity

Triplication of human chromosome 21, or trisomy 21 (T21), causes the condition known as Down syndrome (DS). People with DS show a markedly different disease spectrum relative to typical people, being highly predisposed to conditions such as Alzheimer’s disease, while being protected from other conditions, such as most solid malignancies. Interestingly, people with DS are affected by high rates of autoimmune disorders, whereby the immune system mistakenly attacks healthy tissues. This manuscript reports an exhaustive characterization of the T cells of people with DS, demonstrating many alterations in this key immune cell type that could explain their high risk of autoimmunity. These results reveal opportunities for therapeutic intervention to modulate T cell function and improve health outcomes in DS.

Trisomy 21 (T21) causes Down syndrome (DS), a condition characterized by high prevalence of autoimmune disorders. However, the molecular and cellular mechanisms driving this phenotype remain unclear. Building upon our previous finding that T cells from people with DS show increased expression of interferon (IFN)-stimulated genes, we have completed a comprehensive characterization of the peripheral T cell compartment in adults with DS with and without autoimmune conditions. CD8+ T cells from adults with DS are depleted of naïve subsets and enriched for differentiated subsets, express higher levels of markers of activation and senescence (e.g., IFN-γ, Granzyme B, PD-1, KLRG1), and overproduce cytokines tied to autoimmunity (e.g., TNF-α). Conventional CD4+ T cells display increased differentiation, polarization toward the Th1 and Th1/17 states, and overproduction of the autoimmunity-related cytokines IL-17A and IL-22. Plasma cytokine analysis confirms elevation of multiple autoimmunity-related cytokines (e.g., TNF-α, IL17A–D, IL-22) in people with DS, independent of diagnosis of autoimmunity. Although Tregs are more abundant in DS, functional assays show that CD8+ and CD4+ effector T cells with T21 are resistant to Treg-mediated suppression, regardless of Treg karyotype. Transcriptome analysis of white blood cells and T cells reveals strong signatures of T cell differentiation and activation that correlate positively with IFN hyperactivity. Finally, mass cytometry analysis of 8 IFN-inducible phosphoepitopes demonstrates that T cell subsets with T21 show elevated levels of basal IFN signaling and hypersensitivity to IFN-α stimulation. Therefore, these results point to T cell dysregulation associated with IFN hyperactivity as a contributor to autoimmunity in DS.

Progress in interleukin-2 therapy for rheumatic immune diseases by regulating the immune balance of T cells

Breaking the balance between effector T cells, including Th17 (T helper cell 17) cells, and regulatory T cells (Tregs) is a key link in the pathogenesis of rheumatic immune diseases, which lead to a new concept of regulating immune balance in the treatment of rheumatic immune diseases. Interleukin (IL)-2 can effectively regulate the differentiation, development and functional activity of regulatory T cells, thus restoring the immune balance between regulatory T cells and effector T cells. Therefore, low-dose IL-2 has been used in the treatment of rheumatic immune diseases, and it has become a promising new choice to achieve therapeutic purpose by regulating the immune balance of T cell. Here, we discuss the role of T cells immune imbalance in the pathogenesis of rheumatic immune diseases and the mechanism of IL-2 in the treatment of rheumatic immune diseases by regulating T cells immune balance and summarize the relevant clinical trials.

Influence of forkhead box protein 3 polymorphisms (rs2232365, rs3761548) with the outcome of pregnancy: A meta-analysis

Dysfunction of regulatory T cells (Tregs) may contribute to certain immune-related pregnancy complications. Forkhead box protein 3 (FOXP3) is the key transcription factor of Treg. We performed a systematic review and meta-analysis to evaluate the possible association between FOXP3 polymorphisms -924A/G (rs2232365) and -3279C/A (rs3761548) and immune-related pregnancy complications. After reviewing 78 fully published studies, 10 studies fulfilled previously defined eligibility criteria and were used for meta-analysis. Two single nucleotide polymorphisms showed a significant correlation with increased or reduced risk for immune-related pregnancy complications. For rs3761548, women with allele A were significantly at a higher risk than women carrying allele C (odds ratio = 1.29, 95% confidence interval: 1.20-1.38; p = 0.001). For rs2232365, women with GG or AG genotype were at a higher risk than women with genotype AA, thereby, allele G was significantly associated with a higher risk than allele A. Our meta-analysis supports the notion that immune-related pregnancy complications might be linked to genetic variations in the FOXP3 gene.

Immunomics in Pediatric Rheumatic Diseases

The inherent complexity in the immune landscape of pediatric rheumatic disease necessitates a holistic system approach. Uncertainty in the mechanistic workings and etiological driving forces presents difficulty in personalized treatments. The development and progression of immunomics are well suited to deal with this complexity. Immunomics encompasses a spectrum of biological processes that entail genomics, transcriptomics, epigenomics, proteomics, and cytomics. In this review, we will discuss how various high dimensional technologies in immunomics have helped to grow a wealth of data that provide salient clues and biological insights into the pathogenesis of autoimmunity. Interfaced with critical unresolved clinical questions and unmet medical needs, these platforms have helped to identify candidate immune targets, refine patient stratification, and understand treatment response or resistance. Yet the unprecedented growth in data has presented both opportunities and challenges. Researchers are now facing huge heterogeneous data sets from different origins that need to be integrated and exploited for further data mining. We believe that the utilization and integration of these platforms will help unravel the complexities and expedite both discovery and validation of clinical targets.

Varying levels of X chromosome coalescence in female somatic cells alters the balance of X-linked dosage compensation and is implicated in female-dominant systemic lupus erythematosus

The three-dimensional organization of the genome in mammalian interphase nuclei is intrinsically linked to the regulation of gene expression. Whole chromosome territories and their encoded gene loci occupy preferential positions within the nucleus that changes according to the expression profile of a given cell lineage or stage. To further illuminate the relationship between chromosome organization, epigenetic environment, and gene expression, here we examine the functional organization of chromosome X and corresponding X-linked genes in a variety of healthy human and disease state X diploid (XX) cells. We observe high frequencies of homologous chromosome X colocalization (or coalescence), typically associated with initiation of X-chromosome inactivation, occurring in XX cells outside of early embryogenesis. Moreover, during chromosome X coalescence significant changes in Xist, H3K27me3, and X-linked gene expression occur, suggesting the potential exchange of gene regulatory information between the active and inactive X chromosomes. We also observe significant differences in chromosome X coalescence in disease-implicated lymphocytes isolated from systemic lupus erythematosus (SLE) patients compared to healthy controls. These results demonstrate that X chromosomes can functionally interact outside of embryogenesis when X inactivation is initiated and suggest a potential gene regulatory mechanism aberration underlying the increased frequency of autoimmunity in XX individuals.

T-Cell Compartmentalization and Functional Adaptation in Autoimmune Inflammation: Lessons From Pediatric Rheumatic Diseases

Chronic inflammatory diseases are characterized by a disturbed immune balance leading to recurring episodes of inflammation in specific target tissues, such as the joints in juvenile idiopathic arthritis. The tissue becomes infiltrated by multiple types of immune cell, including high numbers of CD4 and CD8 T-cells, which are mostly effector memory cells. Locally, these T-cells display an environment-adapted phenotype, induced by inflammation- and tissue-specific instructions. Some of the infiltrated T-cells may become tissue resident and play a role in relapses of inflammation. Adaptation to the environment may lead to functional (re)programming of cells and altered cellular interactions and responses. For example, specifically at the site of inflammation both CD4 and CD8 T-cells can become resistant to regulatory T-cell-mediated regulation. In addition, CD8 and CD4 T-cells show a unique profile with pro- and anti-inflammatory features coexisting in the same compartment. Also regulatory T-cells are neither homogeneous nor static in nature and show features of functional differentiation, and plasticity in inflammatory environments. Here we will discuss the recent insights in T-cell functional specialization, regulation, and clonal expansion in local (tissue) inflammation.

Inducible IL-7 Hyperexpression Influences Lymphocyte Homeostasis and Function and Increases Allograft Rejection

The IL-7/IL-7R pathway is essential for lymphocyte development and disturbances in the pathway can lead to immune deficiency or T cell mediated destruction. Here, the effect of transient hyperexpression of IL-7 was investigated on immune regulation and allograft rejection under immunosuppression. An experimental in vivo immunosuppressive mouse model of IL-7 hyperexpression was developed using transgenic mice (C57BL/6 background) carrying a tetracycline inducible IL-7 expression cassette, which allowed the temporally controlled induction of IL-7 hyperexpression by Dexamethasone and Doxycycline treatment. Upon induction of IL-7, the B220⁺ c-kit⁺ Pro/Pre-B I compartment in the bone marrow increased as compared to control mice in a serum IL-7 concentration-correlated manner. IL-7 hyperexpression also preferentially increased the population size of memory CD8⁺ T cells in secondary lymphoid organs, and reduced the proportion of CD4⁺Foxp3⁺ T regulatory cells. Of relevance to disease, conventional CD4⁺ T cells from an IL-7-rich milieu escaped T regulatory cell-mediated suppression in vitro and in a model of autoimmune diabetes in vivo. These findings were validated using an IL-7/anti-IL7 complex treatment mouse model to create an IL-7 rich environment. To study the effect of IL-7 on islet graft survival in a mismatched allograft model, BALB/c mice were rendered diabetic by streptozotocin und transplanted with IL-7-inducible or control islets from C57BL/6 mice. As expected, Dexamethasone and Doxycycline treatment prolonged graft median survival as compared to the untreated control group in this transplantation mouse model. However, upon induction of local IL-7 hyperexpression in the transplanted islets, graft survival time was decreased and this was accompanied by an increased CD4⁺ and CD8⁺ T cell infiltration in the islets. Altogether, the findings show that transient elevations of IL-7 can impair immune regulation and lead to graft loss also under immune suppression.

Treg cells in autoimmunity: from identification to Treg-based therapies

Regulatory (Treg) cells are key regulators of inflammation and important for immune tolerance and homeostasis. A major progress has been made in the identification and classification of Treg cells. Due to technological advances, we have gained deep insights in the epigenetic regulation of Treg cells. The use of fate reporter mice allowed addressing the functional consequences of loss of Foxp3 expression. Depending on the environment Treg cells gain effector functions upon loss of Foxp3 expression. However, the traditional view that Treg cells become necessarily pathogenic by gaining effector functions was challenged by recent findings and supports the notion of Treg cell lineage plasticity. Treg cell stability is also a major issue for Treg cell therapies. Clinical trials are designed to use polyclonal Treg cells as therapeutic tools. Here, we summarize the role of Treg cells in selected autoimmune diseases and recent advances in the field of Treg targeted therapies.

Th17/Treg Ratio and Disease Activity in Systemic Lupus Erythematosus

Background:

Systemic lupus erythematosus (SLE) is an autoimmune disease that is characterized by T-cells imbalance. There are ongoing controversies about the role of specific T-helper cell subsets and their cytokines. The study aimed to confirm the disturbance of Th17/Treg ratio in SLE patients.

Methods:

Subjects were SLE patients who met the American College of Rheumatology 1997 criteria. Disease activity assessment was measured by SLAM index. Th17 and Treg level was measured by flow cytometry. Th17 level was evaluated as CD4⁺L17 whilst Treg as CD4⁺Foxp3⁺. Final result is stated as Th17/Treg ratio.

Results:

Thirty female subjects with active SLE had mean SLAM Score of 29.3±3.88, C3 level 25.2 (6-59.5), C4 level 15.25 (5-54.3), ESR 62.1±37.85, CRP 30.16±59.45, and anti-dsDNA 155.32±186.10. Higher Th17 level was found in SLE patients compared to healthy subjects (30.09 pg/ml vs 13.01pg/ml; 12.60% vs 0.91%). However, it did not correlate to disease activity (p>0.05; r=-0.28). Regarding Treg level, there was no significant difference between active SLE and healthy subjects (12.85 vs 11.05 pg/ml; 9.57% vs 2.05%). Treg level negatively correlated to SLE disease activity (p<0.01; r=-0.73). Th17/Treg ratio was 3.28±2.22% and it positively correlated to SLE disease activity (p<0.01; r=0.78).

Conclusion:

Th17/Treg ratio is positively correlated with disease activity. Th17 level is elevated but not correlated with disease activity. Decrease of Treg level is not significant though correlated with disease activity in SLE patients.

The Regulatory T Cell in Active Systemic Lupus Erythematosus Patients: A Systemic Review and Meta-Analysis

Background: Regulatory T cells (Tregs) researches in systemic lupus erythematosus (SLE) have floundered over the years, reports on the numbers and function of Tregs in SLE present quite contradictory results. We therefore conducted a meta-analysis to verify the changes of Tregs in active SLE.

Methods: We systematically searched PubMed, Embase, and ISI web of knowledge databases for eligible articles. In total, 628 active SLE patients and 601 controls from 18 studies were included. Due to a high degree of heterogeneity, a random effects model was used to assess the mean differences in Treg percentages, absolute numbers, and suppression capacities of Tregs between active SLE and controls. Further, subgroup analysis was performed to identify potential sources of heterogeneity.

Results: The pooled percentages of Tregs in active SLE patients were found to be lower than those in controls (−0.864 ± 0.308, p = 0.005), with great heterogeneity (I² = 95.01). The discrepancy of published results might result from the following differences among studies: gating strategies for Tregs, diagnostic criteria for SLE, and thresholds of SLEDAI chosen to differentiate between active and inactive SLE. In active SLE, Tregs gated based on CD25 alone showed lower pooled frequency than those gated by Foxp3⁺ or CD127^low/∅. The percentages of Tregs in active SLE was significantly lower than that in controls when the enrolled SLE patients were diagnosed according to the 1997 modified criteria, whereas they were comparable to controls when diagnosed by the 1982 criteria; the higher threshold of SLEDAI score used to define active SLE tended to achieve a lower percentage of Tregs. The pooled absolute numbers of Tregs in active SLE were significantly decreased compared to those in controls (−1.328 ± 0.374, p < 0.001), but seemed to be unaffected by gating strategies. Suppression capacities of Tregs from active SLE patients showed no abnormalities based on the limited pooled data. Longitudinal monitoring of active SLE showed a significant decrease in Treg percentage at remission.

Conclusions: This study implies that loss of Tregs may play a role in the pathogenesis of active SLE and help clarify contradictory Treg results in SLE.

Regulatory T-cell levels in systemic lupus erythematosus patients: a meta-analysis

Background

The contribution of regulatory T-cells (Tregs) to systemic lupus erythematosus (SLE) pathogenesis remains a matter of debate. The objective of this study was to quantify the association between peripheral blood Tregs and disease status in SLE patients.

Method

EMBASE and PubMed databases were searched using ‘systemic lupus erythematosus’ and ‘regulatory T-cells’ as relevant key terms. A meta-analysis of studies that examined the proportion of Tregs among peripheral blood mononuclear cells (PBMCs) and CD4+T-cells was performed using Stata software. Subgroup analysis was performed based on ethnic groups and Treg definition markers.

Results

The Treg/PBMC and Treg/CD4+T-cell ratios were significantly lower in SLE patients than in healthy controls (HCs), whereas patients with active and inactive SLE showed no difference in these indicators. A subgroup analysis indicated that Asian SLE patients had a substantially lower proportion of Tregs/PBMCs than HCs, but this difference was not seen for white and Latin American SLE patients. Patients defined by CD4+CD25+Foxp3+, CD4+CD25+ and CD4+Foxp3+ had a much lower Treg/PBMC ratio compared with HCs. Ethnic groups and choice of Treg definition markers had no influence on the proportion of Tregs/CD4+T-cells.

Conclusion

The proportion of Tregs among both PBMCs and CD4+T-cells was significantly decreased in SLE patients. Ethnic group and Treg definition markers may influence the proportion of Tregs among PBMCs. Further study of the correlation between SLE disease activity and the proportion of Tregs in peripheral blood is needed to determine the physiological role of this association.

OX40L/OX40 axis impairs follicular and natural Treg function in human SLE

Tregs are impaired in human systemic lupus erythematosus (SLE) and contribute to effector T cell activation. However, the mechanisms responsible for the Treg deficiency in SLE remain unclear. We hypothesized that the OX40L/OX40 axis is implicated in Treg and regulatory follicular helper T (Tfr) cell dysfunction in human SLE. OX40L/OX40 axis engagement on Tregs and Tfr cells not only specifically impaired their ability to regulate effector T cell proliferation, but also their ability to suppress T follicular helper (Tfh) cell-dependent B cell activation and immunoglobulin secretion. Antigen-presenting cells from patients with active SLE mediated Treg dysfunction in an OX40L-dependent manner, and OX40L-expressing cells colocalized with Foxp3+ cells in active SLE skin lesions. Engagement of the OX40L/OX40 axis resulted in Foxp3 downregulation in Tregs, and expression in SLE Tregs correlated with the proportion of circulating OX40L-expressing myeloid DCs. These data support that OX40L/OX40 signals are implicated in Treg dysfunction in human SLE. Thus, blocking the OX40L/OX40 axis appears to be a promising therapeutic strategy.

Immunosuppressive therapy influences the accelerated age-dependent T-helper cell differentiation in systemic lupus erythematosus remission patients

Background

CD4⁺ T cells are of great importance in the pathogenesis of systemic lupus erythematosus (SLE), as an imbalance between CD4⁺ regulatory T cells (Tregs) and CD4⁺ responder T cells (Tresps) causes flares of active disease in SLE patients. In this study, we aimed to find the role of aberrant Treg/Tresp cell differentiation for maintaining Treg/Tresp cell balance and Treg functionality.

Methods

To determine differences in the differentiation of Tregs/Tresps we calculated the percentages of CD45RA⁺CD31⁺ recent thymic emigrant (RTE) Tregs/Tresps and CD45RA⁺CD31⁻ mature naive (MN) Tregs/Tresps, as well as CD45RA⁻CD31⁺ and CD45RA⁻CD31⁻ memory Tregs/Tresps (CD31⁺ and CD31⁻ memory Tregs/Tresps) within the total Treg/Tresp pool of 78 SLE remission patients compared with 94 healthy controls of different ages. The proliferation capacity of each Treg/Tresp subset was determined by staining the cells with anti-Ki67 monoclonal antibodies. Differences in the autologous or allogeneic Treg function between SLE remission patients and healthy controls were determined using suppression assays.

Results

With age, we found an increased differentiation of RTE Tregs via CD31⁺ memory Tregs and of RTE Tresps via MN Tresps into CD31⁻ memory Tregs/Tresp in healthy volunteers. This opposite differentiation of RTE Tregs and Tresps was associated with an age-dependent increase in the suppressive activity of both naive and memory Tregs. SLE patients showed similar age-dependent Treg cell differentiation. However, in these patients RTE Tresps differentiated increasingly via CD31⁺ memory Tresps, whereby CD31⁻ memory Tresps arose that were much more difficult to inhibit for Tregs than those that emerged through differentiation via MN Tresps. Consequently, the increase in the suppressive activity of Tregs with age could not be maintained in SLE patients. Testing the Tregs of healthy volunteers and SLE patients with autologous and nonautologous Tresps revealed that the significantly decreased Treg function in SLE patients was not exclusively attributed to an age-dependent diminished sensitivity of the Tresps for Treg suppression. The immunosuppressive therapy reduced the accelerated age-dependent Tresp cell proliferation to normal levels, but simultaneously inhibited Treg cell proliferation below normal levels.

Conclusions

Our data reveal that the currently used immunosuppressive therapy has a favorable effect on the differentiation and proliferation of Tresps but has a rather unfavorable effect on the proliferation of Tregs. Newer substances with more specific effects on the immune system would be desirable.

Electronic supplementary material

The online version of this article (10.1186/s13075-018-1778-6) contains supplementary material, which is available to authorized users.

Altered frequency of Th17 and Treg cells in new-onset systemic lupus erythematosus patients

BACKGROUND

T helper 17 (Th17) and regulatory T (Treg) cells play an important role in pathogenesis of systemic lupus erythematosus (SLE). Their imbalance was reported in treated SLE patients, while very little is known about the relationship between Th17 and Treg cells in new-onset untreated SLE patients.

AIM

To assess the role of Th17/Treg cells in the pathogenesis of new-onset SLE.

MATERIALS AND METHODS

Thirty-nine new-onset SLE patients and 33 age-matched healthy adults were enrolled. We analysed Th17 and Treg cells in different level, including their frequencies in peripheral blood mononuclear cell, the expression of interleukin-17 A (IL-17A) and forkhead box P3 (FoxP3) proteins, the expression of retinoid-related orphan nuclear receptor γt (RORγt) and FoxP3 genes and plasma level of IL-17A.

RESULTS

The frequency of Th17 and Treg cells, the expression of IL-17A among Th17 cell, the plasma level of IL-17A, the expression of RORγt and FoxP3 genes were all significantly higher in SLE patients. Th17 cells were negatively correlated with Treg cells. We also found that plasma level of IL-17A was positively correlated with SLE disease activities index (SLEDAI) scores and an equation among the level of C3, IgA, IL-17A and SLEDAI scores.

CONCLUSIONS

Results indicate that Th17 and Treg cells take roles in the pathogenesis of SLE. Th17 cells might suppress the differentiation of Treg cells, and feedback effects might exist between them during SLE pathogenesis. The measure of plasma level of IL-17A may be useful for evaluation of disease activity in new-onset SLE patients.

Increased CD4+CD25-Foxp3+ T cells in Chinese systemic lupus erythematosus: correlate with disease activity and organ involvement

Objective

The increment of CD4+CD25−Foxp3+T cells has been reported in systemic lupus erythematosus (SLE) patients. However, the exact identity of this T cell subset is still unclear. Thus, we analyzed CD4+CD25−Foxp3+T cells and Treg cells (CD4+CD25+Foxp3+ T cells) in a large sample of Chinese SLE patients in different disease states.

Methods

A total of 280 SLE patients and 38 healthy volunteers were enrolled, which included 21 patients with untreated new-onset lupus (UNOL), 13 patients with drug withdrawal more than 6 months and 246 patients with treatments. Phenotypic and functional analysis of peripheral blood CD4+CD25−Foxp3+ T cells and Treg cells were performed by flow cytometry. The correlation of CD4+CD25−Foxp3+T cells and Treg cells with disease activity, clinical indicators and organ involvement were analyzed.

Results

CD4+CD25−Foxp3+ T cells and Treg cells were significantly increased in SLE patients and showed significantly positive correlations with disease activity. CD4+CD25−Foxp3+ T cells were significantly increased in patients with skin and hematologic involvement as well as arthritis. Diverse changes between CD4+CD25−Foxp3+ T cells and Treg cells when faced with different medications, especially HCQ and MMF. CD4+CD25−Foxp3+ T cells expressed more IFN-γ and less CTLA-4 than CD4+CD25+Foxp3+ T cells, which were similar to CD4+CD25+Foxp3− T cells, and expressed similar IL-17, ICOS and Helios to CD4+CD25+Foxp3+ T cells. The synthesis capacity of IL-10 of CD4+CD25−Foxp3+ T cells and the expression of GITR on CD4+CD25−Foxp3+ T cells were between CD4+CD25+Foxp3+ and CD4+CD25+Foxp3− T cells.

Conclusions

Our results indicate that increased CD4+CD25−Foxp3+ T cells in lupus patients, which combined the features of suppression and pro-inflammatory, may serve as a biomarker for disease activity and organ involvement in SLE.

IL-6: a cytokine at the crossroads of autoimmunity

IL-6 is implicated in the development and progression of autoimmune diseases in part by influencing CD4 T cell lineage and regulation. Elevated IL-6 levels drive inflammation in a wide range of autoimmune diseases, some of which are also characterized by enhanced T cell responses to IL-6. Notably, the impact of IL-6 on inflammation is contextual in nature and dependent on the cell type, cytokine milieu and tissue. Targeting the IL-6/IL-6R axis in humans has been shown to successfully ameliorate a subset of autoimmune conditions. In this review, we discuss recent studies investigating how IL-6 regulates the CD4 T cell response in the context of autoimmune disease and highlight how blocking different aspects of the IL-6 pathway is advantageous in the treatment of disease.

The Proportion of Regulatory T Cells in Patients with Systemic Lupus Erythematosus: A Meta-Analysis

Background

Accumulating evidence indicates that a deficiency in or dysfunction of regulatory T cells (Tregs) is involved in the pathogenesis of systemic lupus erythematosus (SLE). As different markers have been used to identify Tregs, recent studies on the proportions of Tregs in SLE patients have generated controversial results. To clarify the status of Tregs in such patients, we determined the proportions of Tregs present during development of the disease, with special consideration of controversial cellular markers.

Methods

We identified studies reporting the proportions of Tregs in SLE patients by searching relevant databases through March 2018. Using the PRISMA guidelines, we performed a random effects meta-analysis of the frequencies of Tregs defined in different ways. Inconsistency was evaluated using the I-squared index (I²), and publication bias was assessed by examining funnel plot asymmetry using the Begger and Egger tests.

Results

Forty-four studies involving 2779 participants were included in the meta-analysis. No significant difference in the proportions of Tregs was evident between 1772 patients and 1007 controls [−0.191, (−0.552, 0.362), p = 0.613, I² = 95.7%]. We next conducted subanalyses based on individual definitions of Tregs. When the Treg definition included “FOXP3-positive” cells, the proportions did not differ between SLE patients and controls [−0.042, (−0.548, 0.632), p = 0.889, I² = 96.6%]; this was the case when Tregs were defined as either “CD25^low/−FOXP3⁺” or “CD25^high/+FOXP3⁺” cells. SLE patients had lower proportions of Tregs that were “single CD25-positive” [−1.428, (−1.982, −0.873), p < 0.001, I² = 93.4%] and “CD127-negative” [−1.093, (−2.002, −0.183), p = 0.018, I² = 92.6%] compared to controls. Tregs defined as “CD25^bright,” “CD25^bright/highCD127^low/−,” and “CD25^highCD127^low/−FOXP3⁺” did not differ in proportion between SLE patients and controls.

Conclusions

The Treg proportions varied by the cellular identification method used. The proportions of Tregs that were accurately identified and functionally validated fell among patients with SLE. Stricter definitions of Tregs are necessary when evaluating the status of such patients.

Effector T Cell Resistance to Suppression and STAT3 Signaling during the Development of Human Type 1 Diabetes

Dysregulation of regulatory T cell (Treg)-mediated suppression and, in particular, resistance of CD4⁺ effector T cells (Teffs) to suppression have been implicated in the pathogenesis of human type 1 diabetes (T1D). However, the mechanistic basis behind this resistance and the time frame during which it develops in relation to the onset of clinical T1D remain unclear. In this study, we analyzed the capacity of peripheral blood Teffs isolated both from patients with T1D and from prediabetic at-risk subjects positive for multiple diabetes-associated autoantibodies (AAb⁺) to be suppressed by Tregs. Because STAT3 activation through IL-6 has previously been implicated in mediating Teff resistance, we also investigated the surface expression of IL-6R as well as IL-6- and TCR-mediated phosphorylation of STAT3 in T cells from our study subjects. Teff resistance to suppression was observed both in patients with newly diagnosed and long-standing T1D but not in AAb⁺ subjects and was shown to be STAT3 dependent. No alterations in IL-6R expression or IL-6-mediated STAT3 activation were observed in T cells from patients with T1D or AAb⁺ subjects. However, faster STAT3 activation after TCR stimulation without concomitant increase in IL-6 expression was observed in T cells from patients with T1D. These experiments suggest that Teff resistance in T1D patients is STAT3 dependent but not directly linked with the capacity of Teffs to produce or respond to IL-6. In conclusion, Teff resistance to Treg-mediated suppression is likely a feature of disease progression in human T1D and can potentially be targeted by immune therapies that block STAT3 activation.

Regulatory T Cells Compensation Failure Cause the Dysregulation of Immune Response in Pristane Induced Lupus Mice Model

Introduction

Regulatory T cells' (Tregs') role remains unclear in the pathogenesis of systemic lupus erythematosus (SLE). This study was aimed at monitoring the percentage of Tregs within 32 weeks and monitoring its relationship with the percentage of other T helper (Th) cell subsets and the levels of autoantibodies and pro-inflammatory cytokines in a murine SLE model induced by pristane.

Methods

Forty-eight female BALB/c mice were divided into a healthy control (HC) and a pristine-induced (PI) group. SLE was induced by a single 0.5 cc pristane intraperitoneal injection. Six from each group were sacrificed every eight weeks until 32 weeks post-pristane injection. Treg, Th1, Th2 and Th17 percentages from the spleen were measured using flowcytometry. ANA, IL-6 and IFN-α levels were measured from serum using ELISA.

Results

The Treg percentage from the PI group increased significantly at 16 weeks compared to the HC group, while Th1, Th2 and Th17 percentages decreased. Tregs in the PI group began to reduce from the 24th to 32nd weeks, followed by an elevation of the Th1, Th2 and Th17 percentages. Tregs were negatively correlated with Th1 and Th2. Tregs in the PI group had a negative correlation with ANA and IFN-α levels from serum, whereas Tregs had a positive correlation with IL-6 levels.

Conclusion

The compensation of Tregs observed at 16 weeks after pristane injection failed, marked by a decreasing number of Tregs, followed by an increase of Th subsets, pro-inflammatory cytokines and autoantibodies. This compensatory failure of Tregs could be affected by pro-inflammatory cytokines, such as IFN-α and IL-6.

CD4+CD45RA-FOXP3low Regulatory T Cells as Potential Biomarkers of Disease Activity in Systemic Lupus Erythematosus Brazilian Patients

Heren, we analyzed Treg cells as potential biomarkers of disease activity in systemic lupus erythematosus (SLE) patients. Peripheral blood mononuclear cells from 30 SLE patients (15 active: SLEDAI > 6/15 SLE remission: SLEDAI< 6) and 15 healthy volunteers were purified. Treg immunophenotyping was performed using CD4, CD25, CD45, CD127, and FOXP3 markers. CD4⁺FOXP3⁺ Treg activation state was investigated based on CD45RA and FOXP3 expression. To increase the accuracy of our findings, a multivariate linear regression was performed. We showed a significant increase in the frequency of CD4⁺FOXP3⁺ Treg cells in SLE patients. However, unlike all other Treg cells phenotypes analyzed, only eTreg (CD4⁺FOXP3^highCD45RA^-) (p=0.01) subtype was inversely correlated with disease activity while Foxp3⁺nontreg (CD4⁺FOXP3^lowCD45RA^-) (p=0.003) exerted a direct influence in the outcome of the disease. Foxp3⁺nontreg cells were the most consistent SLE active indicator, confirmed by multiple linear regression analyses. In summary, our results demonstrate Foxp3⁺nontreg cells as new biomarkers in the search of an effective therapeutic strategy in SLE.

Potential Immune Biomarkers in Diagnosis and Clinical Management for Systemic Lupus Erythematosus

BACKGROUND

There is still no reliable, specific biomarker for precision diagnosis and clinical monitoring of systemic lupus erythematosus. The aim of this study was to investigate the importance of the determination of immunofenotypic profiles (T, B lymphocytes and NK cells) and serum cytokine concentrations (IL-17 and IFN-alpha) as potential biomarkers for this disease.

METHODS

The study included 55 patients with SLE and 25 healthy controls. The proportion of T, B, NK cells were assessed in peripheral blood using flow cytometric assays while the serum cytokine concentration (IL-17 and IFNalpha) was determined by ELISA test.

RESULTS

ROC curve analysis showed good accuracy to distinguish between patients and healthy individuals for activated T cells (AUC=0.798; p<0.001), Treg (AUC= 0.651; p=0.036), and memory B cells (AUC=0.285; p=0.002). We found statistically significant difference (p=0.036) in the levels of serum IL-17 between patients with SLE (IL-17=49.27 pg/mL) and controls (IL-17= 28.64 pg/mL).

CONCLUSIONS

Significant increase in the relative number of Treg lymphocytes, and decrease in memory B cells, as well as decrease level of IL-17, in SLE patients may be implicated in the pathogenesis of the disease. These parameters, as biomarkers, could distinguish SLE patients and no-SLE patients. Monitoring subpopulations of immune cells in peripheral blood using flow cytometry provides insight into abnormal T and B cell function in SLE. Progress in understanding the immunity at SLE, results in concrete benefits for the SLE patients, which include new clinical management and therapeutic strategies.

LPS-treated bone marrow-derived dendritic cells induce immune tolerance through modulating differentiation of CD4+ regulatory T cell subpopulations mediated by 3G11 and CD127

Intravenous transfer of LPS-treated bone marrow-derived dendritic cells blocks development of autoimmunity induced by CD4⁺ T cells in vivo. However, cellular mechanisms of dendritic cell-mediated immune tolerance have not yet been fully elucidated. Here, we report that there are two new subpopulations of CD4⁺CD25⁺FoxP3⁺GITR⁺ regulatory T cells (CD127⁺3G11⁺ and CD127⁺3G11^- cells). LPS-treated dendritic cells facilitate development of CD4⁺CD127⁺3G11^- regulatory T cells but inhibit that of CD4⁺CD127⁺3G11⁺ regulatory T cells. LPS-induced tolerogenic dendritic cells may cause immune tolerance through modulating balance of different subsets of CD4⁺ regulatory T cells mediated by CD127 and 3G11. Our results imply a new potential cellular mechanism of dendritic cell-mediated immune tolerance.