Phenotype and function of natural killer cells in systemic lupus erythematosus: excess interferon-γ production in patients with active disease

Targeting EZH2 in autoimmune diseases: unraveling epigenetic regulation and therapeutic potential

Approximately 8-10% of the global population is affected by autoimmune diseases (ADs), which encompass a wide array of idiopathic conditions resulting from dysregulated immune responses. The enzymatic component of the polycomb-repressive complex 2 (PRC2), enhancer of zeste homolog 2 (EZH2, also referred to as KMT6), functions as a methyltransferase possessing a SET domain that plays crucial roles in epigenetic regulation, explicitly facilitating the methylation of histone H3 at lysine 27. Notably, EZH2 is catalytically inactive and requires association with EED and SUZ12 to form an active PRC2 complex. Hyperactivation of EZH2 has been implicated in various malignancies, prompting the development of EZH2 inhibitors as therapeutic agents for several cancers, including lymphoma, prostate, breast, and colon cancer. The application of EZH2-targeting therapies has also been explored in the context of autoimmune diseases. While there have been advancements in certain ADs, responses can vary significantly, as evidenced by mixed outcomes in cases such as inflammatory bowel disease. Consequently, the dual role of EZH2 and the therapeutic potential of its inhibitors in the treatment of ADs remain nascent fields of study. This review will elucidate the interplay between EZH2 and autoimmune diseases, highlighting emerging insights and therapeutic avenues.

Identification and immunoassay of biomarkers associated with T cell exhaustion in systemic lupus erythematosus

Background

Systemic lupus erythematosus (SLE) is an autoimmune disease with unclear etiology. T cell exhaustion (TEX) suppresses the immune response and can be a potential therapeutic strategy for autoimmune diseases. Therefore, this study primarily investigated the mechanism by which TEX influences SLE, offering a novel target for its treatment.

Methods

GSE72326 and GSE81622 were utilized in this study. TEX related genes (TEX-RGs) were obtained from the published literature. Differentially expressed genes (DEGs) were obtained through differential expression analysis. Subsequently, candidate genes were selected by overlapping DEGs and TEX-RGs. These candidate genes underwent protein-protein interactions (PPIs) analysis for further screening. Machine learning was applied to identify candidate key genes from the PPI-identified genes. The candidate key genes exhibiting an area under the receiver operating characteristic (ROC) curve (AUC) greater than 0.7, along with consistent expression trends and significant differences in GSE72326 and GSE81622 were defined as biomarkers. Additionally, enrichment analysis, immune infiltration analysis, chemical compounds prediction and molecular docking were carried out. Importantly, the biomarkers were validated for expression by reverse transcription-quantitative polymerase chain reaction (RT-qPCR).

Results

The biomarkers MX1, LY6E, IFI44 and OASL were screened by overlapping 327 DEGs and 1,408 TEX-RGs. Gene set enrichment analysis (GSEA) showed that there was a significant positive correlation between the expression of these biomarkers and immune-related pathways, such as the NOD-like receptor signaling pathway, Toll-like receptor signaling pathway and RIG-I-like receptor signaling pathway significant positive correlation. The immune infiltration of 8 types of immune cells differed significantly in SLE. Naive B cells, resting memory CD4 T cells and resting NK cells were significantly down-regulated in the SLE group. 4 biomarkers showed the highest correlation with resting memory CD4 T cells. Bisphenol A targeted OASL and LY6E, whereas acetaminophen targeted IFI44 and MX1.The binding activity between the biomarkers and the chemical compounds targeting them was very strong. Finally, RT-qPCR expression of MX1, LY6E, IFI44 and OASL was consistent with the results of the dataset.

Conclusion

MX1, LY6E, IFI44 and OASL were identified as biomarkers related to TEX in SLE. These biomarkers could be detected in the blood for early diagnosis of the disease or to monitor the efficacy of the disease treatment, thus providing a new target for the management of SLE.

Immune complex deposition promotes NK cell accumulation in the kidney

In systemic lupus erythematosus, immune complexes deposited in the kidney vasculature represent a potent inflammatory trigger with a high potential to progress to glomerulonephritis and organ failure. These immune complexes can be recognized by multiple effector cells via complement and Fcγ receptors. The transcriptome of CD16-bearing NK cells has been documented in kidneys from patients with SLE. In this study, we show that NK cells accumulate in the kidney in response to immune complex deposition and modulate the behavior of local T cells. Depletion of NK cells transiently ameliorated disease, suggesting NK cells may play a role in lupus nephritis and other immune complex-mediated conditions.

The Absence of Thyroid-Stimulating Hormone Receptor Expression on Natural Killer T Cells: Implications for the Immune-Endocrine Interaction

The expression of thyroid-stimulating hormone receptor (TSHR) has been documented on various immune cells, including B lymphocytes, T lymphocytes, Natural Killer (NK) cells, monocytes, and dendritic cells (DCs). Natural Killer T (NKT) cells serve as a crucial link between innate and adaptive immunity, playing significant roles in immunological interactions and autoimmune diseases. The aim of the present study was to evaluate the presence of TSHR on NKT cells. Our research involved patients with thyroid disease, as well as healthy controls. Peripheral blood mononuclear cells (PBMCs) and, thereafter, NKT cells were isolated from 86 patients with benign nodular thyroid disease with and without autoimmune thyroid disease (AITD) (28 and 56 cases, respectively), and TSHR expression was analyzed using fluorescence-activated cell sorting (FACS). In order to confirm the results, the reverse-transcription polymerase chain reaction (RT-PCR) method was used in cells obtained from healthy individuals. Our findings obtained with application of the FACS method revealed that TSHR is not expressed on NKT cells in either AITD or non-AITD patients, though TSHR was detected in the total PBMC population (TSHR+ cells 2.77%). The absence of TSHR on NKT cells was further confirmed with RT-PCR in healthy individuals (p < 0.0001). These results questioned the previously suggested direct influence of NKT cells on AITD development.

Potential of resveratrol in the treatment of systemic lupus erythematosus (Review)

Systemic lupus erythematosus (SLE) is a multi‑system chronic autoimmune disease with a complex occurrence and development process, associated with immune disorders, uncertain prognosis, and treatment modalities which vary by patient and disease activity. At present, the clinical treatment of SLE mainly focuses on hormones and immunosuppressants. In recent years, the research on new treatment strategies for SLE has been booming, and strong preclinical results and clinical research have promoted the development of numerous drugs (such as rituximab and orencia), but numerous of these drugs have failed to achieve effectiveness in clinical trials, and there are some adverse reactions. Recent evidence suggests that resveratrol (RSV) has the effect of ameliorating immune disorders by inhibiting overactivation of immune cells. In the present review, advances in research on the protective effects and potential mechanisms of RSV against SLE are summarized and the potential potency of RSV and its use as a promising therapeutic option for the treatment of SLE are highlighted.

Active juvenile systemic lupus erythematosus is associated with distinct NK cell transcriptional and phenotypic alterations

While adaptive immune responses have been studied extensively in SLE (systemic lupus erythematosus), there is limited and contradictory evidence regarding the contribution of natural killer (NK) cells to disease pathogenesis. There is even less evidence about the role of NK cells in the more severe phenotype with juvenile-onset (J)SLE. In this study, analysis of the phenotype and function of NK cells in a large cohort of JSLE patients demonstrated that total NK cells, as well as perforin and granzyme A expressing NK cell populations, were significantly diminished in JSLE patients compared to age- and sex-matched healthy controls. The reduction in NK cell frequency was associated with increased disease activity, and transcriptomic analysis of NK populations from active and low disease activity JSLE patients versus healthy controls confirmed that disease activity was the main driver of differential NK cell gene expression. Pathway analysis of differentially expressed genes revealed an upregulation of interferon-α responses and a downregulation of exocytosis in active disease compared to healthy controls. Further gene set enrichment analysis also demonstrated an overrepresentation of the apoptosis pathway in active disease. This points to increased propensity for apoptosis as a potential factor contributing to NK cell deficiency in JSLE.

Altered serum levels of cytokines in patients with myasthenia gravis

Background

Myasthenia gravis (MG) is an autoimmune disease characterized by generalized skeletal muscle contraction weakness due to autoantibodies targeting neural-muscular junctions. Here, we investigated the relationship between key cytokines and MG type, disease course, antibodies, and comorbidities.

Method

Cytokine levels in serum samples collected from MG (n = 45) and healthy control (HC, n = 38) patients from January 2020 to June 2022 were quantified via flow cytometry.

Results

Levels of IL-6 were higher in the MG group versus healthy individuals (p = 0.026) and in patients with generalized versus ocular MG (p = 0.019). IL-6 levels were positively correlated with QMG score. In patients with MG with both AChR and Titin antibodies, serum levels of sFas and granulysin were higher than in those with AChR alone (p = 0.036, and p = 0.028, respectively). LOMG had a reduction in serum levels of IL-2 compared to EOMG (p = 0.036). LOMG patients with diabetes had lower serum levels of IL-2, IL-4, and IFN-γ (p = 0.044, p = 0.038, and p = 0.047, respectively) versus those without diabetes. sFas in the MG with Abnormal thymus were reduced compared to those in MG with Normal thymus (p = 0.008).

Conclusions

This study revealed a positive correlation between IL-6 level and MG status. Serum cytokine levels of the AChR + Titin MG group differed from those of the AChR group. LOMG had a lower IL-2 level. Comorbidities affect some cytokines in peripheral blood in MG serum.

Increased ILT2+ natural killer T cells correlate with disease activity in systemic lupus erythematosus

OBJECTIVE

Numerous immune cell types, such as B and T lymphocytes, natural killer cells (NK), and NKT cells, are related to the pathogenesis of diseases in systemic lupus erythematosus (SLE). Our goal in this investigation is to examine the phenotype of NK cells and NKT cells alterations in individuals with SLE.

METHODS

Typically, 50 SLE patients and 24 age-matched healthy people had their PBMCs obtained. Employing flow cytometry, the phenotype of NK and NKT cells and immunoglobulin-like transcript 2 (ILT2) expressions were identified. ELISA was utilized to evaluate the amounts of interleukin-15 (IL-15) and sHLA-G in the serum.

RESULTS

The frequencies of the circulating NK and NKT cells in individuals with SLE were decreased compared to healthy controls. Furthermore, ILT2 expression was significantly increased in NKT cells, but showed no obvious change in NK cells. Clinical severity and active nephritis were substantially associated with ILT2+ NKT cell frequencies. The correlation study showed that the upregulation of ILT2 expression was related to sHLA-G in plasma but not to IL-15.

CONCLUSIONS

ILT2+ NKT cells have a vital function in the immune abnormalities of SLE, which can also supply a viable goal for therapeutic intervention. Key Points •ILT2 expression was significantly increased in NKT cells in SLE patients. •ILT2+ NKT cell frequencies were associated with clinical severity which may be used as an indicator for evaluating disease activity in patients with SLE.

Natural Killer Cell Count in Systemic Lupus Erythematosus Patients: A Flow Cytometry-Based Study

Background Natural killer cells (NK cells) are important mediators of innate immune regulation and literature has shown that they have a role in shaping the adaptive immune system. Objective The present study was undertaken to analyze the NK cell count in systemic lupus erythematosus (SLE) patients as compared to that of controls. Materials and methods Safety of Estrogens in Lupus Erythematosus National Assessment SLE Disease Activity Index (SELENA-SLEDAI) score was assessed in 32 SLE cases. CD3(-) cells were identified as NK cells on flow cytometry, and then their subsets CD56(+) and CD16(+) cells were identified compared to 30 healthy controls. Receiver Operating Characteristic (ROC) curve analysis was performed on NK cells to attempt to determine a cut-off point. Results The CD3(-) NK cells, including the percentages of CD56(+) and CD16(+), were significantly (p<0.001) reduced in SLE patients (12.35%, and 18.7%) as compared to controls (24.67%, and 46.6%). On ROC curve analysis, cut-off values <481/cumm with sensitivity of 86.7% and specificity of 84.4% for CD3(-) NK cells (p<0.001), <23% with 60% sensitivity and 75% specificity for CD56(+) NK cells (p<0.001), and <29% with sensitivity of 70% and specificity of 87.5% for CD16(+) NK cells (p<0.001) were noted. Subsets of NK cells showed no association with the clinicopathological parameters like age, sex, disease activity, anti-nuclear antibodies (ANA), dsDNA, absolute lymphocyte count, and renal involvement. Conclusion NK cells, and their subpopulations of CD56(+) and CD16(+) cells, are decreased in patients with SLE as compared to controls.

Exercise-induced modulation of Interferon-signature: a therapeutic route toward management of Systemic Lupus Erythematosus

Systemic Lupus Erythematosus (SLE) is a multisystemic autoimmune disorder characterized by flares-ups/remissions with a complex clinical picture related to disease severity and organ/tissue injury, which, if left untreated, may result in permanent damage. Enhanced fatigue and pain perception, worsened quality of life (QoL) and outcome are constant, albeit symptoms may differ. An aberrant SLE immunoprofiling, note as "interferon (IFN)α-signature", is acknowledged to break immunotolerance. Recently, a deregulated "IFNγ-signature" is suggested to silently precede/trigger IFNα profile before clinical manifestations. IFNα- and IFNγ-over-signaling merge in cytokine/chemokine overexpression exacerbating autoimmunity. Remission achievement and QoL improvement are the main goals. The current therapy (i.e., corticosteroids, immunosuppressants) aims to downregulate immune over-response. Exercise could be a safe treatment due to its ever-emerging ability to shape and re-balance immune system without harmful side-effects; in addition, it improves cardiorespiratory capacity and musculoskeletal strength/power, usually impaired in SLE. Nevertheless, exercise is not yet included in SLE care plans. Furthermore, due to the fear to worsening pain/fatigue, SLE subjects experience kinesiophobia and sedentary lifestyle, worsening physical health. Training SLE patients to exercise is mandatory to fight inactive behavior and ameliorate health. This review aims to focus the attention on the role of exercise as a non-pharmacological therapy in SLE, considering its ability to mitigate IFN-signature and rebalance (auto)immune response. To this purpose, the significance of IFNα- and IFNγ-signaling in SLE etiopathogenesis will be addressed first and discussed thereafter as biotarget of exercise. Comments are addressed on the need to make aware all SLE care professional figures to promote exercise for health patients.

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.

Peripheral blood natural killer cell cytotoxicity in recurrent miscarriage: a systematic review and meta-analysis

Dysregulated natural killer (NK) cells have been associated with recurrent miscarriages (RM). Studies have suggested that high peripheral blood NK cell cytotoxicities (pNKCs) are associated with an increased risk of RM. The aim of this systematic review (SR) and meta-analysis (MAs) is to investigate the difference in pNKC between nonpregnant and pregnant women with RM and controls and determine whether pNKC is reduced by immunotherapy. We searched the PubMed/Medline, Embase, and Web of Science databases. The MAs were conducted to compare pNKCs between women with and without RM before and during pregnancy as well as pre- and post-immunotherapy. Risk of bias in nonrandomized studies was assessed by the Newcastle-Ottawa Scale. Statistical analysis was performed using the Review Manager software. A total of 19 studies were included in the SR and 14 studies in the MAs. The MAs revealed higher pNKCs among nonpregnant women with RM compared to controls (MD, 7.99 95 %CI 6.40-9.58; p < 0.00001). pNKCs were also higher in pregnant women with RM than in pregnant controls (MD, 8.21 95 %CI 6.08-10.34; p < 0.00001). Women with RM showed significantly decreased pNKCs after the immunotherapy compared to before (MD, -8.20 95 %CI -10.20 - -6.19; p < 0, 00001). Additionally, there is an association between high pNKCs and the risk of pregnancy loss in women with RM. However, included studies showed substantial heterogeneities regarding the inclusion criteria of patients, techniques measuring pNKC, and types of immunotherapies. More studies are needed to evaluate the clinical efficiency of pNKCs in managing RM.

CSL362 potently and specifically depletes pDCs invitro and ablates SLE-immune complex-induced IFN responses

Systemic lupus erythematosus (SLE) is an autoimmune disease with significant morbidity and mortality. Type I interferon (IFN) drives SLE pathology and plasmacytoid dendritic cells (pDCs) are potent producers of IFN; however, the specific effects of pDC depletion have not been demonstrated. We show CD123 was highly expressed on pDCs and the anti-CD123 antibody CSL362 potently depleted pDCs in vitro. CSL362 pre-treatment abrogated the induction of IFNα and IFN-induced gene transcription following stimulation with SLE patient-derived serum or immune complexes. RNA transcripts induced in pDCs by ex vivo stimulation with TLR ligands were reflected in gene expression profiles of SLE blood, and correlated with disease severity. TLR ligand-induced protein production by SLE patient peripheral mononuclear cells was abrogated by CSL362 pre-treatment including proteins over expressed in SLE patient serum. These findings implicate pDCs as key drivers in the cellular activation and production of soluble factors seen in SLE.

KLRG1 is reduced on NK cells in SLE patients, inversely correlates with disease activity and is modulated by hydroxychloroquine in vitro

OBJECTIVES

Killer cell lectin-like receptor G 1 (KLRG1), a transmembrane receptor with inhibitory capacity expressed in human immune cells, emerged as a novel susceptibility gene for systemic lupus erythematosus (SLE). The aim of this study was to investigate the expression of KLRG1 in SLE patients compared to healthy controls (HC) on both NK and T cells and to evaluate its possible involvement in SLE pathogenesis.

METHODS

Eighteen SLE patients and twelve healthy controls were enrolled. Peripheral blood mononuclear cells (PBMCs) from these patients were phenotypically characterized by immunofluorescence and flow cytometry. The effect of the hydroxychloroquine (HCQ) in vitro on KLRG1 expression and its signaling mediated functions in NK cells were analyzed.

RESULTS

KLRG1 expression was significantly reduced on the analyzed immune cell populations in SLE patients compared to HC, especially on total NK cells. Moreover, expression of KLRG1 on total NK cells inversely correlated with the SLEDAI-2K. A direct association between KLRG1 expression on NK cells and patients' treatment with HCQ was observed. In vitro treatment with HCQ increased KLRG1 expression on NK cells. In HC, KLRG1+ NK cells showed reduced degranulation and IFNγ production, while in SLE patient, this inhibition occurred only for the IFNγ production.

CONCLUSION

With this study we revealed a reduced expression and an impaired function of KLRG1 on NK cells in SLE patients. These results suggest a possible role of KLRG1 in the pathogenesis of SLE and as a novel biomarker of this disease.

Identification of the shared genes and immune signatures between systemic lupus erythematosus and idiopathic pulmonary fibrosis

BACKGROUND

Systemic lupus erythematosus (SLE) is an autoimmune disorder which could lead to inflammation and fibrosis in various organs. Pulmonary fibrosis is a severe complication in patients with SLE. Nonetheless, SLE-derived pulmonary fibrosis has unknown pathogenesis. Of pulmonary fibrosis, Idiopathic pulmonary fibrosis (IPF) is a typicality and deadly form. Aiming to investigate the gene signatures and possible immune mechanisms in SLE-derived pulmonary fibrosis, we explored common characters between SLE and IPF from Gene Expression Omnibus (GEO) database.

RESULTS

We employed the weighted gene co-expression network analysis (WGCNA) to identify the shared genes. Two modules were significantly identified in both SLE and IPF, respectively. The overlapped 40 genes were selected out for further analysis. The GO enrichment analysis of shared genes between SLE and IPF was performed with ClueGO and indicated that p38MAPK cascade, a key inflammation response pathway, may be a common feature in both SLE and IPF. The validation datasets also illustrated this point. The enrichment analysis of common miRNAs was obtained from the Human microRNA Disease Database (HMDD) and the enrichment analysis with the DIANA tools also indicated that MAPK pathways' role in the pathogenesis of SLE and IPF. The target genes of these common miRNAs were identified by the TargetScan7.2 and a common miRNAs-mRNAs network was constructed with the overlapped genes in target and shared genes to show the regulated target of SLE-derived pulmonary fibrosis. The result of CIBERSORT showed decreased regulatory T cells (Tregs), naïve CD4+ T cells and rest mast cells but increased activated NK cells and activated mast cells in both SLE and IPF. The target genes of cyclophosphamide were also obtained from the Drug Repurposing Hub and had an interaction with the common gene PTGS2 predicted with protein-protein interaction (PPI) and molecular docking, indicating its potential treatment effect.

CONCLUSIONS

This study originally uncovered the MAPK pathway, and the infiltration of some immune-cell subsets might be pivotal factors for pulmonary fibrosis complication in SLE, which could be used as potentially therapeutic targets. The cyclophosphamide may treat SLE-derived pulmonary fibrosis through interaction with PTGS2, which could be activated by p38MAPK.

Association between type I interferon pathway activation and clinical outcomes in rheumatic and musculoskeletal diseases: a systematic literature review informing EULAR points to consider

BACKGROUND

Type I interferons (IFN-I) contribute to a broad range of rheumatic and musculoskeletal diseases (RMDs). Compelling evidence suggests that the measurement of IFN-I pathway activation may have clinical value. Although several IFN-I pathway assays have been proposed, the exact clinical applications are unclear. We summarise the evidence on the potential clinical utility of assays measuring IFN-I pathway activation.

METHODS

A systematic literature review was conducted across three databases to evaluate the use of IFN-I assays in diagnosis and monitor disease activity, prognosis, response to treatment and responsiveness to change in several RMDs.

RESULTS

Of 366 screened, 276 studies were selected that reported the use of assays reflecting IFN-I pathway activation for disease diagnosis (n=188), assessment of disease activity (n=122), prognosis (n=20), response to treatment (n=23) and assay responsiveness (n=59). Immunoassays, quantitative PCR (qPCR) and microarrays were reported most frequently, while systemic lupus erythematosus (SLE), rheumatoid arthritis, myositis, systemic sclerosis and primary Sjögren's syndrome were the most studied RMDs. The literature demonstrated significant heterogeneity in techniques, analytical conditions, risk of bias and application in diseases. Inadequate study designs and technical heterogeneity were the main limitations. IFN-I pathway activation was associated with disease activity and flare occurrence in SLE, but their incremental value was uncertain. IFN-I pathway activation may predict response to IFN-I targeting therapies and may predict response to different treatments.

CONCLUSIONS

Evidence indicates potential clinical value of assays measuring IFN-I pathway activation in several RMDs, but assay harmonisation and clinical validation are urged. This review informs the EULAR points to consider for the measurement and reporting of IFN-I pathway assays.

EZH2: Its regulation and roles in immune disturbance of SLE

The pathogenesis of systemic lupus erythematosus (SLE) is related to immune homeostasis imbalance. Epigenetic mechanisms have played a significant role in breaking immune tolerance. Enhancer of zeste homolog 2 (EZH2), the specific methylation transferase of lysine at position 27 of histone 3, is currently found to participate in the pathogenesis of SLE through affecting multiple components of the immune system. This review mainly expounds the mechanisms underlying EZH2-mediated disruption of immune homeostasis in SLE patients, hoping to provide new ideas in the pathogenesis of SLE and new targets for future treatment.

The phenotype of CD3-CD56bright and CD3-CD56dim natural killer cells in systemic lupus erythematosus patients and its relation to disease activity

Introduction

Systemic lupus erythematosus (SLE) patients have decreased natural killer (NK) cell counts. The decrease in the number of NK cells has implications for a decrease in the function of NK cells which can affect the progression of SLE disease. The study aim was to determine profiles of CD3-CD56^bright and CD3-CD56^dim NK cells in SLE patients and their relation to disease activity.

Material and methods

This study included 36 patients of SLE who fulfilled the ACR 1997/SLICC 2012 criteria, women aged 18-49 years. Disease activity was assessed by the Mex-SLEDAI. Peripheral blood samples from SLE patients were analyzed by flow cytometry to evaluate NK cell subsets, according to differential expression of the main subset of NK cells, which is CD3-CD56^bright and CD3-CD56^dim.

Results

The mean percentage of regulatory NK cell count (CD3-CD56^bright) in active SLE patients was significantly lower (p = 0.000) than in inactive SLE patients. The mean percentage of cytotoxic NK cell count (CD3-CD56^dim) in active SLE patients was significantly (p = 0.000) higher than in inactive SLE patients. A correlation was observed between two subsets of NK cells with disease activity (p = 0.00). The percentage of CD3-CD56^bright NK cells was negatively correlated with disease activity (r = -0.766), whereas the percentage of CD3-CD56^dim NK cells positively correlated with disease activity (r = 0.761).

Conclusions

There is a difference in the mean percentage of the number of NK cells (CD3-CD56+) in both a subset of regulatory NK cells (CD3-CD56^bright) and cytotoxic NK cells (CD3-CD56^dim) in active and inactive SLE patients and it is closely related to SLE disease activity.

Implications of NKG2A in immunity and immune-mediated diseases

In recent studies, NKG2A is revealed to be a key immune checkpoint for both natural killer (NK) cells and CD8⁺ T cells. It form heterodimer receptors with CD94, and targets the peptide-presenting human leukocyte antigen-E (HLA-E) molecules. Upon crosslinking, NKG2A/CD94 delivers inhibitory signals for NK cells and CD8⁺ T cells, while blocking NKG2A can effectively unleash functions of these cytotoxic lymphocytes. The interaction between NKG2A and HLA-E contributes to tumor immune escape, and NKG2A-mediated mechanisms are currently being exploited to develop potential antitumor therapeutic strategies. In addition, growing evidence shows that NKG2A also plays important roles in other immune-related diseases including viral infections, autoimmune diseases, inflammatory diseases, parasite infections and transplant rejection. Therefore, the current work focuses on describing the effect of NKG2A on immune regulation and exploring its potential role in immune-mediated disorders.

Role of the innate and adaptive immune responses in the pathogenesis of systemic lupus erythematosus

OBJECTIVE

Systemic lupus erythematosus (SLE), the most common form of lupus, is a multisystemic rheumatic disease with different clinical features that generally affect women of childbearing age. The common symptoms of SLE are very similar to other autoimmune and non-autoimmune disorders, thereby it is known as a thousand faces disease. In this article, we are going to discuss some of the most updated information about immune system-related factors, cells, and cytokines involved in SLE pathogenesis.

METHODS

Different electronic databases, especially PubMed/MEDLINE, Scopus, and Google Scholar, were searched to review and analyze relevant literature on the role of innate and adaptive immune cells and cytokines in the pathogenesis of SLE. A search for relevant literature was accomplished using various keywords including systemic lupus erythematosus, apoptosis, autoantibodies, immunopathogenesis of SLE, adaptive and innate immune cells, inflammatory cytokines, hormones, etc. RESULTS AND CONCLUSION: The most important characteristic of SLE is the production of antibodies against different nuclear autoantigens like double-strand DNA and RNA. The depositions of the immune complexes (ICs) that are generated between autoantibodies and autoantigens, along with aberrant clearance of them, can lead to permanent inflammation and contribute to tissue or organ damage. Related mechanisms underlying the initiation and development of SLE have not been clarified yet. Although, defects in immune tolerance, enhanced antigenic load, hyperactivity of T cells, and inappropriate regulation of B cells contribute to the pathogenic autoantibodies generation. Besides, sex hormones that influence the immune system seem to act as triggers or protectors of SLE development.

Mesenchymal stem cells and natural killer cells interaction mechanisms and potential clinical applications

Natural killer cells (NK cells) are innate immune cells that are activated to fight tumor cells and virus-infected cells. NK cells also play an important role in the graft versus leukemia response. However, they can over-develop inflammatory reactions by secreting inflammatory cytokines and increasing Th1 differentiation, eventually leading to tissue damage. Today, researchers have attributed some autoimmune diseases and GVHD to NK cells. On the other hand, it has been shown that mesenchymal stem cells (MSCs) can modulate the activity of NK cells, while some researchers have shown that NK cells can cause MSCs to lysis. Therefore, we considered it is necessary to investigate the effect of these two cells and their signaling pathway in contact with each other, also their clinical applications.

Molecular Mechanisms of Immunosenescene and Inflammaging: Relevance to the Immunopathogenesis and Treatment of Multiple Sclerosis

Aging is characterized, amongst other features, by a complex process of cellular senescence involving both innate and adaptive immunity, called immunosenescence and associated to inflammaging, a low-grade chronic inflammation. Both processes fuel each other and partially explain increasing incidence of cancers, infections, age-related autoimmunity, and vascular disease as well as a reduced response to vaccination. Multiple sclerosis (MS) is a lifelong disease, for which considerable progress in disease-modifying therapies (DMTs) and management has improved long-term survival. However, disability progression, increasing with age and disease duration, remains. Neurologists are now involved in caring for elderly MS patients, with increasing comorbidities. Aging of the immune system therefore has relevant implications for MS pathogenesis, response to DMTs and the risks mediated by these treatments. We propose to review current evidence regarding markers and molecular mechanisms of immunosenescence and their relevance to understanding MS pathogenesis. We will focus on age-related changes in the innate and adaptive immune system in MS and other auto-immune diseases, such as systemic lupus erythematosus and rheumatoid arthritis. The consequences of these immune changes on MS pathology, in interaction with the intrinsic aging process of central nervous system resident cells will be discussed. Finally, the impact of immunosenescence on disease evolution and on the safety and efficacy of current DMTs will be presented.

Increased oxidative stress contributes to impaired peripheral CD56dimCD57+ NK cells from patients with systemic lupus erythematosus

Background

Systemic lupus erythematosus (SLE) is characterized by loss of immune tolerance and imbalance of immune cell subsets. Natural killer (NK) cells contribute to regulate both the innate and adaptive immune response. In this study, we aimed to detect alterations of peripheral NK cells and explore intrinsic mechanisms involving in NK cell abnormality in SLE.

Methods

Blood samples from healthy controls (HCs) and patients with SLE and rheumatoid arthritis (RA) were collected. The NK count, NK subsets (CD56^bright, CD56^dimCD57⁻, and CD56^dimCD57⁺), phenotypes, and apoptosis were evaluated with flow cytometer. Mitochondrial reactive oxygen species (mtROS) and total ROS levels were detected with MitoSOX Red and DCFH-DA staining respectively. Published data (GSE63829 and GSE23695) from Gene Expression Omnibus (GEO) was analyzed by Gene Set Enrichment Analysis (GSEA).

Results

Total peripheral NK count was down-regulated in untreated SLE patients in comparison to that in untreated RA patients and HCs. SLE patients exhibited a selective reduction in peripheral CD56^dimCD57⁺ NK cell proportion, which was negatively associated with disease activity and positively correlated with levels of complement(C)3 and C4. Compared with HCs, peripheral CD56^dimCD57⁺ NK cells from SLE patients exhibited altered phenotypes, increased endogenous apoptosis and higher levels of mtROS and ROS. In addition, when treated with hydrogen peroxide (H₂O₂), peripheral CD56^dimCD57⁺ NK cell subset was more prone to undergo apoptosis than CD56^dimCD57⁻ NK cells. Furthermore, this NK cell subset from SLE patients exhibited impaired cytotoxicity in response to activated CD4⁺ T cells in vitro.

Conclusion

Our study demonstrated a selective loss of mature CD56^dimCD57⁺ NK cell subset in SLE patients, which may caused by preferential apoptosis of this subset under increased oxidative stress in SLE. The attenuated in vitro cytotoxicity of CD56^dimCD57⁺ NK cells may contribute to the impaired ability of eliminating pathogenic CD4⁺ T cells in SLE.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13075-022-02731-y.

Small RNAs encoded by human endogenous retrovirus K overexpressed in PBMCs may contribute to the diagnosis and evaluation of systemic lupus erythematosus as novel biomarkers

This study aimed to identify the genes and small RNAs (sRNAs) expressed by the human endogenous retrovirus K (HERV-K) HML2 and their associations with the immune process of systemic lupus erythematosus (SLE). RNA-Seq data including 99 SLE patients and 18 controls (GSE72420) was obtained from the Gene Expression Omnibus. Differentially expressed genes (DEGs) as well as HML2-DEGs between SLE patients and normal controls were identified. Five HML2-DEGs involved in immune-regulating function were identified using weighted gene co-expression network analysis (WGCNA). The associations between these genes and the proportions of immune cells were determined by CIBERSORT. Ten candidate HML2-encoded sRNAs were identified based on specific criteria, and three of them were further validated in SLE patients by qRT-PCR. The diagnostic values of these three sRNAs were evaluated in SLE and lupus nephritis (LN). This study suggested that HML2 genes and their encoded sRNAs might be involved in the immune regulation and progress of SLE. These potential sRNAs might function as regulatory molecules and diagnostic biomarkers of SLE and LN.

Interleukin-2 and regulatory T cells in rheumatic diseases

Failure of regulatory T (T_reg) cells to properly control immune responses leads invariably to autoimmunity and organ damage. Decreased numbers or impaired function of T_reg cells, especially in the context of inflammation, has been documented in many human autoimmune diseases. Restoration of T_reg cell fitness and/or expansion of their numbers using low-dose natural IL-2, the main cytokine driving T_reg cell survival and function, has demonstrated clinical efficacy in early clinical trials. Genetically modified IL-2 with an extended half-life and increased selectivity for T_reg cells is now in clinical development. Administration of IL-2 combined with therapies targeting other pathways involved in the expression of autoimmune diseases should further enhance its therapeutic potential. Ongoing clinical efforts that capitalize on the early clinical success of IL-2 treatment should bring the use of this cytokine to the forefront of biological treatments for autoimmune diseases.

The impact of sex on susceptibility to systemic lupus erythematosus and rheumatoid arthritis; a bioinformatics point of view

The unknown etiology of systemic autoimmune diseases, such as Systemic Lupus Erythematosus (SLE) and Rheumatoid Arthritis (RA), with a remarkable predominance of female, have prompted many researchers for unveiling the precise molecular mechanisms involved in this gender bias. In fact, depending on hormones and transcribed genes from sex chromosomes, at least, the initial mechanisms involved in pathogenesis might differ largely. With the aim of elucidating the above mechanisms, we have tried to specify the differentially expressed genes (DEGs) extracted from microarray libraries from both female and male SLE and RA patients. Subsequently, the androgen and estrogen receptor elements (ARE and ERE) among differentially expressed transcription factors (TFs) and the DEGs located on X or Y chromosomes have been determined. Moreover, the pathways regarding the common DEGs in both sexes are enriched. Our data revealed several ARE and ERE-containing genes (LCN2, LTF, RPL31, RPL9, RPS17, RPS24, RPS27L, S100A8, ABCA1, HIST1H2BD, ISG15, MAFB, GNLY, EVL, and HDC) to be associated with the related autoimmune disease and sex. Also, two DEGs (KDM5D and RPS4Y1) in SLE patients were determined to be on Y chromosome with one had been proved to be associated with autoantigens in SLE. Altogether, our data showed a number of plausible pathways in both autoimmune conditions together with the relevance of several sex-related genes in the mentioned diseases pathogenesis.

NK Cell Patterns in Idiopathic Inflammatory Myopathies with Pulmonary Affection

BACKGROUND

Pulmonary affection (PA) is associated with a substantial increase in morbidity and mortality in patients with idiopathic inflammatory myopathies (IIM). However, the underlying immune mechanisms of PA remain enigmatic and prompt deeper immunological analyses. Importantly, the Janus-faced role of natural killer (NK) cells, capable of pro-inflammatory as well as regulatory effects, might be of interest for the pathophysiologic understanding of PA in IIM.

METHODS

To extend our understanding of immunological alterations in IIM patients with PA, we compared the signatures of NK cells in peripheral blood using multi-color flow cytometry in IIM patients with (n = 12, of which anti-synthetase syndrome = 8 and dermatomyositis = 4) or without PA (n = 12).

RESULTS

We did not observe any significant differences for B cells, CD4, and CD8 T cells, while total NK cell numbers in IIM patients with PA were reduced compared to non-PA patients. NK cell alterations were driven by a particular decrease of CD56^dim NK cells, while CD56^bright NK cells remained unchanged. Comparisons of the cell surface expression of a large panel of NK receptors revealed an increased mean fluorescence intensity of NKG2D⁺ on NK cells from patients with PA compared with non-PA patients, especially on the CD56^dim subset. NKG2D⁺ and NKp46⁺ cell surface levels were associated with reduced vital capacity, serving as a surrogate marker for clinical severity of PA.

CONCLUSION

Our data illustrate that PA in IIM is associated with alterations of the NK cell repertoire, suggesting a relevant contribution of NK cells in certain IIMs, which might pave the way for NK cell-targeted therapeutic approaches.

Single-cell multi-omics analysis reveals IFN-driven alterations in T lymphocytes and natural killer cells in systemic lupus erythematosus

Background: The characterisation of the peripheral immune system in the autoimmune disease systemic lupus erythematosus (SLE) at the single-cell level has been limited by the reduced sensitivity of current whole-transcriptomic technologies. Here we employ a targeted single-cell multi-omics approach, combining protein and mRNA quantification, to generate a high-resolution map of the T lymphocyte and natural killer (NK) cell populations in blood from SLE patients. Methods: We designed a custom panel to quantify the transcription of 534 genes in parallel with the expression of 51 surface protein targets using the BD Rhapsody AbSeq single-cell system. We applied this technology to profile 20,656 T and NK cells isolated from peripheral blood from an SLE patient with a type I interferon (IFN)-induced gene expression signature (IFN hi), and an age- and sex- matched IFN low SLE patient and healthy donor. Results: We confirmed the presence of a rare cytotoxic CD4 + T cell (CTL) subset, which was exclusively present in the IFN hi patient. Furthermore, we identified additional alterations consistent with increased immune activation in this patient, most notably a shift towards terminally differentiated CD57 + CD8 + T cell and CD16 + NK dim phenotypes, and the presence of a subset of recently-activated naïve CD4 + T cells. Conclusions: Our results identify IFN-driven changes in the composition and phenotype of T and NK cells that are consistent with a systemic immune activation within the IFN hi patient, and underscore the added resolving power of this multi-omics approach to identify rare immune subsets. Consequently, we were able to find evidence for novel cellular peripheral biomarkers of SLE disease activity, including a subpopulation of CD57 + CD4 + CTLs.

Increased TIM-3+PD-1+ NK cells are associated with the disease activity and severity of systemic lupus erythematosus

It is well established that natural killer (NK) cells are dysregulated in systemic lupus erythematosus (SLE) patients. However, the functions of NK cells and the mechanisms regulated by them in SLE remain incompletely understood. Patients with SLE were recruited from The First Affiliated Hospital of Nanchang University, and their clinical characteristics and treatments were recorded. The expression levels of T cell immunoglobulin mucin-3 (TIM-3) and programmed cell death protein 1 (PD-1) on NK cells were examined using flow cytometry. The correlations between the increase in TIM-3⁺PD-1⁺ NK cells in the SLE patients and clinical traits, including inflammatory markers, auto-antibodies, disease activity and severity of SLE, were examined. The TIM-3⁺NK cells, PD-1⁺NK cells and TIM-3⁺PD-1⁺ NK cells were significantly increased in the SLE patients. The increase in TIM-3⁺PD-1⁺ NK cells in the patients with SLE was associated with erythrocyte sedimentation rate, C-reactive protein, anti-double stranded DNA, anti-ribosomal P, SLE disease activity index and clinical features. The frequency of TIM-3⁺PD-1⁺NK cells in SLE patients with a cardiovascular disease (CVD) was significantly lower than that in SLE patients without a CVD. Moreover, the increased TIM-3⁺PD-1⁺ NK cells were significantly decreased in SLE patients following treatment. The present study suggested that the increased TIM-3⁺PD-1⁺ NK cells were associated with the disease activity and severity of SLE and may play a role in SLE pathogenesis.

Novel Long Non-coding RNA Expression Profile of Peripheral Blood Mononuclear Cells Reveals Potential Biomarkers and Regulatory Mechanisms in Systemic Lupus Erythematosus

Objective

The multisystem involvement and high heterogeneity of systemic lupus erythematosus (SLE) lead to great challenges in its diagnosis and treatment. The purpose of this study was to find new lncRNAs in peripheral blood mononuclear cells of SLE patients by transcriptome sequencing and explore their potential as biomarkers and their correlation with clinical features.

Materials and Methods

Transcriptome sequencing was used to screen differentially expressed lncRNAs (DELs) and mRNAs (DEMs). The expression of these selected lncRNAs and mRNAs in SLE patients and healthy controls was verified by qPCR. DAVID and WebGestalt were used to perform enrichment analysis. Cytoscape was used to construct a protein-protein network, a coexpression network, and a competitive endogenous RNA network to reveal the regulatory mechanisms of lncRNAs at the transcriptome level.

Results

A total of 1737 DELs and 4078 DEMs were identified between SLE patients and healthy controls. Ten lncRNAs and eight genes were verified by qPCR in a larger sample set. The lncRNA NONHSAT101022.2 was significantly downregulated in SLE patients and was also significantly related to the activity and severity of disease. The upregulated genes were enriched in defense and the immune response, while the downregulated genes were mainly enriched in SLE-related pathways. Topology network analysis revealed that the lncRNAs were involved in regulation at the transcriptome level, including acting directly on mRNA or indirectly affecting gene expression by acting on miRNA.

Conclusion

In this work, we identified many mRNAs and novel lncRNAs by transcriptome sequencing. The functions and regulatory mechanisms of these lncRNAs were analyzed by bioinformatic methods. The novel lncRNA NONHSAT101022.2 is significantly downregulated in SLE patients and is significantly related to the activity and severity of disease. Additionally, we propose that NONHSAT101022.2 may enhance the signal transduction of β2-AR by cis regulating LMBRD2, inducing NK cells to produce high levels of IFN-γ and thereby exacerbating SLE.

Increased Concentrations of Circulating Soluble MHC Class I-Related Chain A (sMICA) and sMICB and Modulation of Plasma Membrane MICA Expression: Potential Mechanisms and Correlation With Natural Killer Cell Activity in Systemic Lupus Erythematosus

Systemic lupus erythematosus (SLE) is a severe autoimmune disease of unknown etiology. The major histocompatibility complex (MHC) class I-related chain A (MICA) and B (MICB) are stress-inducible cell surface molecules. MICA and MICB label malfunctioning cells for their recognition by cytotoxic lymphocytes such as natural killer (NK) cells. Alterations in this recognition have been found in SLE. MICA/MICB can be shed from the cell surface, subsequently acting either as a soluble decoy receptor (sMICA/sMICB) or in CD4⁺ T-cell expansion. Conversely, NK cells are frequently defective in SLE and lower NK cell numbers have been reported in patients with active SLE. However, these cells are also thought to exert regulatory functions and to prevent autoimmunity. We therefore investigated whether, and how, plasma membrane and soluble MICA/B are modulated in SLE and whether they influence NK cell activity, in order to better understand how MICA/B may participate in disease development. We report significantly elevated concentrations of circulating sMICA/B in SLE patients compared with healthy individuals or a control patient group. In SLE patients, sMICA concentrations were significantly higher in patients positive for anti-SSB and anti-RNP autoantibodies. In order to study the mechanism and the potential source of sMICA, we analyzed circulating sMICA concentration in Behcet patients before and after interferon (IFN)-α therapy: no modulation was observed, suggesting that IFN-α is not intrinsically crucial for sMICA release in vivo. We also show that monocytes and neutrophils stimulated in vitro with cytokines or extracellular chromatin up-regulate plasma membrane MICA expression, without releasing sMICA. Importantly, in peripheral blood mononuclear cells from healthy individuals stimulated in vitro by cell-free chromatin, NK cells up-regulate CD69 and CD107 in a monocyte-dependent manner and at least partly via MICA-NKG2D interaction, whereas NK cells were exhausted in SLE patients. In conclusion, sMICA concentrations are elevated in SLE patients, whereas plasma membrane MICA is up-regulated in response to some lupus stimuli and triggers NK cell activation. Those results suggest the requirement for a tight control in vivo and highlight the complex role of the MICA/sMICA system in SLE.

The Role of Natural Killer Cells in Autoimmune Diseases

Natural killer (NK) cells, the large granular lymphocytes differentiated from the common lymphoid progenitors, were discovered in early 1970's. They are members of innate immunity and were initially defined by their strong cytotoxicity against virus-infected cells and by their important effector functions in anti-tumoral immune responses. Nowadays, NK cells are classified among the recently discovered innate lymphoid cell subsets and have capacity to influence both innate and adaptive immune responses. Therefore, they can be considered as innate immune cells that stands between the innate and adaptive arms of immunity. NK cells don't express T or B cell receptors and are recognized by absence of CD3. There are two major subgroups of NK cells according to their differential expression of CD16 and CD56. While CD16+CD56dim subset is best-known by their cytotoxic functions, CD16-CD56bright NK cell subset produces a bunch of cytokines comparable to CD4+ T helper cell subsets. Another subset of NK cells with production of interleukin (IL)-10 was named as NK regulatory cells, which has suppressive properties and could take part in immune-regulatory responses. Activation of NK cells is determined by a delicate balance of cell-surface receptors that have either activating or inhibitory properties. On the other hand, a variety of cytokines including IL-2, IL-12, IL-15, and IL-18 influence NK cell activity. NK-derived cytokines and their cytotoxic functions through induction of apoptosis take part in regulation of the immune responses and could contribute to the pathogenesis of many immune mediated diseases including ankylosing spondylitis, Behçet's disease, multiple sclerosis, rheumatoid arthritis, psoriasis, systemic lupus erythematosus and type-1 diabetes. Dysregulation of NK cells in autoimmune disorders may occur through multiple mechanisms. Thanks to the rapid developments in biotechnology, progressive research in immunology enables better characterization of cells and their delicate roles in the complex network of immunity. As NK cells stand in between innate and adaptive arms of immunity and "bridge" them, their contribution in inflammation and immune regulation deserves intense investigations. Better understanding of NK-cell biology and their contribution in both exacerbation and regulation of inflammatory disorders is a requisite for possible utilization of these multi-faceted cells in novel therapeutic interventions.

Basophils as a potential marker of lupus nephritis by flow cytometry

Objective:

To establish a convenient and simple flow cytometry immunophenotyping panel to explore immune cellular alterations and potential cellular biomarkers in systemic lupus erythematosus.

Materials and methods:

This is a cross-sectional, case–control study including 60 patients with systemic lupus erythematosus and 20 sex- and age-matched healthy controls. A 14-color immunophenotyping panel was applied to detect proportions of circulating immune mononuclear cells, and comparisons between patients and healthy controls, and subgroups of patients, were performed. Correlations between cellular proportions and other parameters were investigated.

Results:

After multivariate analysis, significantly decreased proportions of CD4⁻CD8⁻ T cells, natural killer cells and innate lymphoid cells were observed in patients compared with healthy controls. The proportions of basophils were decreased significantly in patients with lupus nephritis (LN) compared with those in patients without LN.

Conclusion:

In the present study, we found that basophil proportions may be a biomarker of LN.

Systemic lupus erythematosus is a chronic, multisystem, autoimmune disorder that involves various abnormalities of immune cells and thus presents in a striking variety of ways. This study aimed to establish a biomarker panel that would enable the exploration of changes in immune cells and the relationships between immune cell subsets and clinical manifestations in patients with systemic lupus erythematosus. Our results showed that basophil cell proportions may be a biomarker of use in lupus nephritis.

Role of IL-24 in NK cell activation and its clinical implication in systemic lupus erythematosus

OBJECTIVES

Interleukin (IL)-24 has been considered as an inflammatory cytokine in autoimmune diseases. However, conflicting data exist and its biological function remains controversial. Additionally, little is known about its functional impact on natural killer (NK) cells. The aim of this study was to investigate the role of IL-24 in NK cell activation and its clinical implication in systemic lupus erythematosus (SLE).

METHODS

Serum cohort consisting of 299 SLE patients, 214 RA patients, and 159 healthy controls (HCs) and plasma cohort consisting of 70 SLE patients, 82 RA patients, and 123 HCs were included in evaluating IL-24 concentrations. Impact of IL-24 on NK cell activation was assessed in two NK cell subsets, i.e., CD56^dimCD16⁺ and CD56^brightCD16^- NK cells. Human NK-92 cell line was applied to evaluate functional potential of IL-24 on NK cell migration and invasion.

RESULTS

Serum and plasma levels of IL-24 were comparable between patients with SLE or RA and HCs. While recombinant human (rh) IL-2 consistently induced an increased expression of CD69 on both CD56^dimCD16⁺ and CD56^brightCD16^- cells derived from both healthy subjects and patients with SLE, IL-24 alone was insufficient to activate the CD56^dim and CD56^bright NK cells. Similarly, while the migratory NK-92 cell numbers were significantly increased with rhIL-2 stimulation, IL-24 alone was unable to enhance NK-92 cell migratory and invasive capacity.

CONCLUSION

Our data indicate that there were no significant differences in serum and plasma concentrations of IL-24 between SLE patients and healthy controls. Recombinant IL-24 has no effect on NK cell activation and migration. Key points • This is the first study to investigate functional potential of IL-24 on NK cell activation. • Recombinant IL-24 lacks functional capacity on NK cell activation in either CD56^dimCD16⁺ or CD56^brightCD16^- NK cell subsets derived from both healthy subjects and patients with SLE. • No significant differences in serum and plasma levels of IL-24 between SLE patients and healthy controls.

Natural killer cells in inflammatory autoimmune diseases

Natural killer (NK) cells are a specialised population of innate lymphoid cells (ILCs) that help control local immune responses. Through natural cytotoxicity, production of cytokines and chemokines, and migratory capacity, NK cells play a vital immunoregulatory role in the initiation and chronicity of inflammatory and autoimmune responses. Our understanding of their functional differences and contributions in disease settings is evolving owing to new genetic and functional murine proof-of-concept studies. Here, we summarise current understanding of NK cells in several classic autoimmune disorders, particularly in rheumatoid arthritis (RA), multiple sclerosis (MS), systemic lupus erythematosus (SLE) and type 1 diabetes mellitus (T1DM), but also less understood diseases such as idiopathic inflammatory myopathies (IIMs). A better understanding of how NK cells contribute to these autoimmune disorders may pave the way for NK cell-targeted therapeutics.

An interferon-gamma release assay as a novel biomarker in systemic lupus erythematosus

OBJECTIVE

The mycobacterium tuberculosis (TB) IFN-γ release assay (TB-IGRA) assesses peripheral blood cell release of IFN-γ upon ex vivo exposure to mitogen (IGRA-MT), TB antigen or a negative/nil control (IGRA-NL); IGRA-NL is a measure of spontaneous IFN-γ release (SIR). Here, we investigate the diagnostic associations of elevated SIR and the potential use of IGRA-NL as a novel biomarker in SLE.

METHODS

We analysed diagnostic code frequencies among 11 823 individuals undergoing TB-IGRA testing between 2010 and 2015 in a large urban US health-care system. To study the relationship between IGRA-NL and SLE, we identified 99 individuals with SLE and TB-IGRA test results then assessed correlations between IGRA-NL, normalized IGRA-NL (the quotient of IGRA-NL/IGRA-MT), disease manifestations and disease activity.

RESULTS

We identified a discovery cohort of 108 individuals with elevated SIR (>5 S.d. above median) that was significantly enriched for a limited set of diagnoses, including SLE, TB infection, haemophagocytic lymphohistiocytosis and HIV infection. In SLE patients undergoing TB-IGRA testing, normalized IGRA-NL correlated better with disease activity than did anti-dsDNA or complement levels. This relationship appeared to reflect interactions between normalized IGRA-NL and the presence of acute skin disease, hypocomplementemia, fever and thrombocytopenia.

CONCLUSION

Elevated SIR appears to be associated with a limited number of disease processes, including SLE. The diagnostic utility of SIR remains to be determined. IFN-γ activation, as measured by the TB-IGRA test, may offer a readily available tool for assessing disease activity in patients with SLE.

Tim-3 associated with apoptotic NK cells and disease activity in SLE

T cell immunoglobulin and mucin domain-containing molecule-3 (Tim-3) has been found to play important roles in systemic lupus erythematosus (SLE), however, whether Tim-3 is involved in apoptosis of NK cells in SLE remains unknown. The proportion of CD3−CD56+ NK cells and the percentage of AnnexinV+ NK cells were analyzed by flow cytometry in SLE patients and healthy controls. Tim-3 expression on NK cells was also evaluated by flow cytometry. We firstly observed a decreased proportion of NK cells and an increased proportion of apoptotic NK cells in SLE patients. The proportion of apoptotic NK cells was positively correlated with anti-dsDNA and SLEDAI. Tim-3 expression on NK cells was up-regulated in SLE patients. Further analysis showed that Tim-3 expression on NK cells was negatively correlated with the proportion of apoptotic NK cells, anti-dsDNA and SLEDAI, while positively correlated with the proportion of NK cells. The present results suggest that Tim-3 might play roles in SLE by regulating the apoptosis of NK cells and Tim-3 might serve as a potential target for the treatment of SLE.

Aberrant Non-Coding RNA Expression in Patients with Systemic Lupus Erythematosus: Consequences for Immune Dysfunctions and Tissue Damage

Systemic lupus erythematosus (SLE) is a complex systemic autoimmune disease with heterogeneous clinical manifestations. A diverse innate and adaptive immune dysregulation is involved in the immunopathogenesis of SLE. The dysregulation of immune-related cells may derive from the intricate interactions among genetic, epigenetic, environmental, and immunological factors. Of these contributing factors, non-coding RNAs (ncRNAs), including microRNAs (miRNAs, miRs), and long non-coding RNAs (lncRNAs) play critical roles in the post-transcriptional mRNA expression of cytokines, chemokines, and growth factors, which are essential for immune modulation. In the present review, we emphasize the roles of ncRNA expression in the immune-related cells and cell-free plasma, urine, and tissues contributing to the immunopathogenesis and tissue damage in SLE. In addition, the circular RNAs (circRNA) and their post-translational regulation of protein synthesis in SLE are also briefly described. We wish these critical reviews would be useful in the search for biomarkers/biosignatures and novel therapeutic strategies for SLE patients in the future.

Immunomodulatory effects of cytokine-induced expansion of cytotoxic lymphocytes in a mouse model of lupus-like disease

BACKGROUND AIMS

Certain therapies (e.g., daclizumab) that promote expansion of natural killer (NK) cells are associated with clinical amelioration of disease in the context of multiple sclerosis and associated mouse models. The clinical benefits are putatively attributable to an enhanced capacity of NK cells to kill activated pathogenic T cells. Whether a parallel approach will also be effective in systemic lupus erythematosus (lupus), a multi-organ autoimmune disease driven by aberrant responses of self-reactive T and B cells, is unclear.

METHODS

In the present study, the authors assess the therapeutic impact of IL-2- and IL-15-based strategies for expanding NK cells on measures of lupus-like disease in a mouse model.

RESULTS

Unexpectedly, cytokine-mediated expansion of cytotoxic lymphocytes aggravated immunological measures of lupus-like disease. Depletion studies revealed that the negative effects of these cytokine-based regimens can largely be attributed to expansion of CD8 T cells rather than NK cells.

CONCLUSIONS

These results provoke caution in the use of cytokine-based therapeutics to treat co-morbid cancers in patients with lupus and highlight the need for new methods to selectively expand NK cells to further assess their clinical value in autoimmune disease.

The Emerging Role of Renal Tubular Epithelial Cells in the Immunological Pathophysiology of Lupus Nephritis

Systemic lupus erythematosus (SLE) is a systemic, autoimmune disease that can involve virtually any organ of the body. Lupus nephritis (LN), the clinical manifestation of this disease in the kidney, is one of the most common and severe outcomes of SLE. Although a key pathological hallmark of LN is glomerular inflammation and damage, tubulointerstitial lesions have been recognized as an important component in the pathology of LN. Renal tubular epithelial cells are resident cells in the tubulointerstitium that have been shown to play crucial roles in various acute and chronic kidney diseases. In this context, recent progress has been made in examining the functional role of tubular epithelial cells in LN pathogenesis. This review summarizes recent advances in our understanding of renal tubular epithelial cells in LN, the potential role of tubular epithelial cells as biomarkers in the diagnosis, prognosis, and treatment of LN, and the future therapeutic potential of targeting the tubulointerstitium for the treatment of patients with LN.

Activation status of CD56dim natural killer cells is associated with disease activity of patients with systemic lupus erythematosus

OBJECTIVES

Decreased natural killer (NK) cells have been reported in systemic lupus erythematosus (SLE) patients. However, the role of NK cells in the pathogenesis of SLE is not well understood. In this study, we aimed to characterize NK cell subsets, phenotypes, and cytokine-secreting functions and investigate the clinical relevance of NK cells in SLE patients.

METHODS

Peripheral blood samples from 81 SLE patients and 59 healthy donors (HDs) were collected. The frequency and phenotype of NK cells were measured by flow cytometry. Intracellular interferon-γ (IFN-γ) production by NK cells was evaluated by flow cytometry after stimulation with interleukin-12 (IL-12) and IL-18.

RESULTS

The percentages of NK cells in the peripheral blood of SLE patients were significantly lower than those in HDs, and the percentages of CD56^dim NK cells among total NK cells showed a trend toward decrease. The CD56^dim NK cells in SLE patients showed increased production of IFN-γ and displayed relatively activated phenotypic characteristics, including significant increases in NKp44, NKp46, and CD69 and decreased expression of CD16 and CD158a/h/g. Furthermore, CD56^dim NK cells in active SLE patients had higher percentages of NKp44⁺ cells and lower percentages of CD158a/h/g⁺ cells than those in inactive SLE patients. The percentages of CD158a/h/g⁺ cells among CD56^dim NK cells were negatively correlated with the systemic lupus erythematosus disease activity index (SLEDAI) and positively correlated with C3 and C4 levels.

CONCLUSION

CD56^dim NK cells in SLE patients show a reduced proportion tendency among total NK cells and are activated, which partially reflects the disease activity. CD158a/h/g expression on CD56^dim NK cells may be considered an index of disease activity. Key Points • In patients with SLE, the proportion of CD56^dim NK cells showed a decreased trend and CD56^dim NK cells were phenotypically activated which partially reflects the disease activity. • CD158a/h/g expression on CD56^dim NK cells were decreased which may be used as an indicator for evaluating disease activity in SLE patients.

Current Insights in Cutaneous Lupus Erythematosus Immunopathogenesis

Cutaneous Lupus Erythematosus (CLE) is a clinically diverse group of autoimmune skin diseases with shared histological features of interface dermatitis and autoantibodies deposited at the dermal-epidermal junction. Various genetic and environmental triggers of CLE promote infiltration of T cells, B cells, neutrophils, antigen presenting cells, and NK cells into lesional skin. In this mini-review, we will discuss the clinical features of CLE, insights into CLE immunopathogenesis, and novel treatment approaches.

Type I IFN Drives Experimental Systemic Lupus Erythematosus by Distinct Mechanisms in CD4 T Cells and B Cells

Myriad studies have linked type I IFN to the pathogenesis of autoimmune diseases, including systemic lupus erythematosus (SLE). Although increased levels of type I IFN are found in patients with SLE, and IFN blockade ameliorates disease in many mouse models of lupus, its precise roles in driving SLE pathogenesis remain largely unknown. In this study, we dissected the effect of type I IFN sensing by CD4 T cells and B cells on the development of T follicular helper cells (TFH), germinal center (GC) B cells, plasmablasts, and antinuclear dsDNA IgG levels using the bm12 chronic graft-versus-host disease model of SLE-like disease. Type I IFN sensing by B cells decreased their threshold for BCR signaling and increased their expression of MHC class II, CD40, and Bcl-6, requirements for optimal GC B cell functions. In line with these data, ablation of type I IFN sensing in B cells significantly reduced the accumulation of GC B cells, plasmablasts, and autoantibodies. Ablation of type I IFN sensing in T cells significantly inhibited TFH expansion and subsequent B cell responses. In contrast to the effect in B cells, type I IFN did not promote proliferation in the T cells but protected them from NK cell-mediated killing. Consequently, ablation of either perforin or NK cells completely restored TFH expansion of IFNAR-/- TFH and, subsequently, restored the B cell responses. Together, our data provide evidence for novel roles of type I IFN and immunoregulatory NK cells in the context of sterile inflammation and SLE-like disease.

Dysregulation of TLR9 in neonates leads to fatal inflammatory disease driven by IFN-γ

Recognition of self-nucleic acids by innate immune receptors can lead to the development of autoimmune and/or autoinflammatory diseases. Elucidating mechanisms associated with dysregulated activation of specific receptors may identify new disease correlates and enable more effective therapies. Here we describe an aggressive in vivo model of Toll-like receptor (TLR) 9 dysregulation, based on bypassing the compartmentalized activation of TLR9 in endosomes, and use it to uncover unique aspects of TLR9-driven disease. By inducing TLR9 dysregulation at different stages of life, we show that while dysregulation in adult mice causes a mild systemic autoinflammatory disease, dysregulation of TLR9 early in life drives a severe inflammatory disease resulting in neonatal fatality. The neonatal disease includes some hallmarks of macrophage activation syndrome but is much more severe than previously described models. Unlike TLR7-mediated disease, which requires type I interferon (IFN) receptor signaling, TLR9-driven fatality is dependent on IFN-γ receptor signaling. NK cells are likely key sources of IFN-γ in this model. We identify populations of macrophages and Ly6C^hi monocytes in neonates that express high levels of TLR9 and low levels of TLR7, which may explain why TLR9 dysregulation is particularly consequential early in life, while symptoms of TLR7 dysregulation take longer to manifest. Overall, this study demonstrates that inappropriate TLR9 responses can drive a severe autoinflammatory disease under homeostatic conditions and highlights differences in the diseases resulting from inappropriate activation of TLR9 and TLR7.

Efficacy and safety of low-dose IL-2 in the treatment of systemic lupus erythematosus: a randomised, double-blind, placebo-controlled trial

OBJECTIVES

Open-labelled clinical trials suggested that low-dose IL-2 might be effective in treatment of systemic lupus erythematosus (SLE). A double-blind and placebo-controlled trial is required to formally evaluate the safety and efficacy of low-dose IL-2 therapy.

METHODS

A randomised, double-blind and placebo-controlled clinical trial was designed to treat 60 patients with active SLE. These patients received either IL-2 (n=30) or placebo (n=30) with standard treatment for 12 weeks, and were followed up for additional 12 weeks. IL-2 at a dose of 1 million IU or placebo was administered subcutaneously every other day for 2 weeks and followed by a 2-week break as one treatment cycle. The primary endpoint was the SLE Responder Index-4 (SRI-4) at week 12. The secondary endpoints were other clinical responses, safety and dynamics of immune cell subsets.

RESULTS

At week 12, the SRI-4 response rates were 55.17% and 30.00% for IL-2 and placebo, respectively (p=0.052). At week 24, the SRI-4 response rate of IL-2 group was 65.52%, compared with 36.67% of the placebo group (p=0.027). The primary endpoint was not met at week 12. Low-dose IL-2 treatment resulted in 53.85% (7/13) complete remission in patients with lupus nephritis, compared with 16.67% (2/12) in the placebo group (p=0.036). No serious infection was observed in the IL-2 group, but two in placebo group. Besides expansion of regulatory T cells, low-dose IL-2 may also sustain cellular immunity with enhanced natural killer cells.

CONCLUSIONS

Low-dose IL-2 might be effective and tolerated in treatment of SLE.

TRIAL REGISTRATION NUMBER

ClinicalTrials.gov Registries (NCT02465580 and NCT02932137).