T cell subsets and their role in the pathogenesis of rheumatic disease

A DNA origami device spatially controls CD95 signalling to induce immune tolerance in rheumatoid arthritis

DNA origami is capable of spatially organizing molecules into sophisticated geometric patterns with nanometric precision. Here we describe a reconfigurable, two-dimensional DNA origami with geometrically patterned CD95 ligands that regulates immune cell signalling to alleviate rheumatoid arthritis. In response to pH changes, the device reversibly transforms from a closed to an open configuration, displaying a hexagonal pattern of CD95 ligands with ~10 nm intermolecular spacing, precisely mirroring the spatial arrangement of CD95 receptor clusters on the surface of immune cells. In a collagen-induced arthritis mouse model, DNA origami elicits robust and selective activation of CD95 death-inducing signalling in activated immune cells located in inflamed synovial tissues. Such localized immune tolerance ameliorates joint damage with no noticeable side effects. This device allows for the precise spatial control of cellular signalling, expanding our understanding of ligand-receptor interactions and is a promising platform for the development of pharmacological interventions targeting these interactions.

Lymphocyte subset phenotyping for the prediction of progression to inflammatory arthritis in anti-citrullinated-peptide antibody-positive at-risk individuals

OBJECTIVES

Inflammatory arthritis (IA) is considered the last stage of a disease continuum, where features of systemic autoimmunity can appear years before clinical synovitis. Time to progression to IA varies considerably between at-risk individuals, therefore the identification of biomarkers predictive of progression is of major importance. We previously reported on the value of three CD4+T cell subsets as biomarkers of progression. Here, we aim to establish the value of 18 lymphocyte subsets (LS) for predicting progression to IA.

METHODS

Participants were recruited based on a new musculoskeletal complaint and being positive for anti-citrullinated-peptide antibody. Progression (over 10 years) was defined as the development of clinical synovitis. LS analysis was performed for lymphocyte lineages, naive/memory subsets, inflammation-related cells (IRC) and regulatory cells (Treg/B-reg). Modelling used logistic/Cox regressions.

RESULTS

Of 210 patients included, 93 (44%) progressed to IA, 41/93 (44%) within 12 months (rapid progressors). A total of 5/18 LS were associated with progression [Treg/CD4-naïve/IRC (adjusted P < 0.0001), CD8 (P = 0.021), B-reg (P = 0.015)] and three trends (NK-cells/memory-B-cells/plasmablasts). Unsupervised hierarchical clustering using these eight subsets segregated three clusters of patients, one cluster being enriched [63/109(58%)] and one poor [10/45(22%)] in progressors. Combining all clinical and LS variables, forward logistic regression predicted progression with accuracy = 85.7% and AUC = 0.911, selecting smoking/rheumatoid-factor/HLA-shared-epitope/tender-joint-count-78 and Treg/CD4-naive/CD8/NK-cells/B-reg/plasmablasts. To predict rapid progression, a Cox regression was performed resulting in a model combining smoking/rheumatoid factor and IRC/CD4-naive/Treg/NK-cells/CD8+T cells (AUC = 0.794).

CONCLUSION

Overall, progression was predicted by specific LS, suggesting potential triggers for events leading to the development of IA, while rapid progression was associated with a different set of subsets.

EPCR deficiency ameliorates inflammatory arthritis in mice by suppressing the activation and migration of T cells and dendritic cells

OBJECTIVES

Endothelial protein C receptor (EPCR) is highly expressed in synovial tissues of patients with RA, but the function of this receptor remains unknown in RA. This study investigated the effect of EPCR on the onset and development of inflammatory arthritis and its underlying mechanisms.

METHODS

CIA was induced in EPCR gene knockout (KO) and matched wild-type (WT) mice. The onset and development of arthritis was monitored clinically and histologically. T cells, dendritic cells (DCs), EPCR and cytokines from EPCR KO and WT mice, RA patients and healthy controls (HCs) were detected by flow cytometry and ELISA.

RESULTS

EPCR KO mice displayed >40% lower arthritis incidence and 50% less disease severity than WT mice. EPCR KO mice also had significantly fewer Th1/Th17 cells in synovial tissues with more DCs in circulation. Lymph nodes and synovial CD4 T cells from EPCR KO mice expressed fewer chemokine receptors CXCR3, CXCR5 and CCR6 than WT mice. In vitro, EPCR KO spleen cells contained fewer Th1 and more Th2 and Th17 cells than WT and, in concordance, blocking EPCR in WT cells stimulated Th2 and Th17 cells. DCs generated from EPCR KO bone marrow were less mature and produced less MMP-9. Circulating T cells from RA patients expressed higher levels of EPCR than HC cells; blocking EPCR stimulated Th2 and Treg cells in vitro.

CONCLUSION

Deficiency of EPCR ameliorates arthritis in CIA via inhibition of the activation and migration of pathogenic Th cells and DCs. Targeting EPCR may constitute a novel strategy for future RA treatment.

Augmenting regulatory T cells: new therapeutic strategy for rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic, systemic autoimmune condition marked by inflammation of the joints, degradation of the articular cartilage, and bone resorption. Recent studies found the absolute and relative decreases in circulating regulatory T cells (Tregs) in RA patients. Tregs are a unique type of cells exhibiting immunosuppressive functions, known for expressing the Foxp3 gene. They are instrumental in maintaining immunological tolerance and preventing autoimmunity. Increasing the absolute number and/or enhancing the function of Tregs are effective strategies for treating RA. This article reviews the studies on the mechanisms and targeted therapies related to Tregs in RA, with a view to provide better ideas for the treatment of RA.

A Peripheral Blood Signature of Increased Th1 and Myeloid Cells Combined with Serum Inflammatory Mediators Is Associated with Response to Abatacept in Rheumatoid Arthritis Patients

Abatacept (CTLA4-Ig)-a monoclonal antibody which restricts T cell activation-is an effective treatment for rheumatoid arthritis (RA). Nevertheless, only 50% of RA patients attain clinical responses, while predictors of response are rather limited. Herein, we aimed to investigate for early biomarkers of response to abatacept, based on a detailed immunological profiling of peripheral blood (PB) cells and serum proteins. We applied flow cytometry and proteomics analysis on PB immune cells and serum respectively, of RA patients starting abatacept as the first biologic agent. After 6 months of treatment, 34.5% of patients attained response. At baseline, Th1 and FoxP3+ T cell populations were positively correlated with tender joint counts (p-value = 0.047 and p-value = 0.022, respectively). Upon treatment, CTLA4-Ig effectively reduced the percentages of Th1 and Th17 only in responders (p-value = 0.0277 and p-value = 0.0042, respectively). Notably, baseline levels of Th1 and myeloid cell populations were significantly increased in PB of responders compared to non-responders (p-value = 0.009 and p-value = 0.03, respectively). Proteomics analysis revealed that several inflammatory mediators were present in serum of responders before therapy initiation and strikingly 10 amongst 303 serum proteins were associated with clinical responses. Finally, a composite index based on selected baseline cellular and proteomics' analysis could predict response to abatacept with a high sensitivity (90%) and specificity (88.24%).

Induced regulatory T cells remain suppressive capability on effector T cells and synovial fibroblasts in collagen-induced arthritis

Rheumatoid arthritis (RA) is a common autoimmune disorder initiated by inflammatory synovitis. Hyperproliferation of destructive synovial fibroblasts (SFs) is one of the pathogenic mechanisms of RA. Abnormalities in regulatory T cells (Tregs) may also play a critical role in this progression. To date, it is unclear whether both natural Tregs (nTregs) and induced Tregs (iTregs) share similar characteristics in RA progression and whether Tregs directly suppress the autoaggressive activities of SFs. In this study, we compared suppressive effects on effector T cells (Teffs) and inflamed SFs between nTregs and iTregs in a collagen-induced arthritis (CIA) model. Our results demonstrated that iTregs but not nTregs maintained a suppressive effect on Teffs after adoptive transfer into CIA mice. Additionally, we discovered that iTregs directly inhibited the destructive activities of CIA-SFs. Thus, this study suggests that administration of the iTreg subset has great potential for treatment of RA in the clinic in the future.

The recent progress of myeloid-derived suppressor cell and its targeted therapies in cancers

Myeloid-derived suppressor cells (MDSCs) are an immature group of myeloid-derived cells generated from myeloid cell precursors in the bone marrow. MDSCs appear almost exclusively in pathological conditions, such as tumor progression and various inflammatory diseases. The leading function of MDSCs is their immunosuppressive ability, which plays a crucial role in tumor progression and metastasis through their immunosuppressive effects. Since MDSCs have specific molecular features, and only a tiny amount exists in physiological conditions, MDSC-targeted therapy has become a promising research direction for tumor treatment with minimal side effects. In this review, we briefly introduce the classification, generation and maturation process, and features of MDSCs, and detail their functions under various circumstances. The present review specifically demonstrates the environmental specificity of MDSCs, highlighting the differences between MDSCs from cancer and healthy individuals, as well as tumor-infiltrating MDSCs and circulating MDSCs. Then, we further describe recent advances in MDSC-targeted therapies. The existing and potential targeted drugs are divided into three categories, monoclonal antibodies, small-molecular inhibitors, and peptides. Their targeting mechanisms and characteristics have been summarized respectively. We believe that a comprehensive in-depth understanding of MDSC-targeted therapy could provide more possibilities for the treatment of cancer.

Noninvasive Low-Frequency Pulsed Focused Ultrasound Therapy for Rheumatoid Arthritis in Mice

Rheumatoid arthritis (RA) is a common autoimmune disease characterized by chronic and progressive inflammation of the synovium. Focused ultrasound therapy is an increasingly attractive alternative for treating RA owing to its noninvasiveness; however, it remains unclear which immune subsets respond to ultrasound stimulation. In this study, we showed that spleen-targeted low-frequency pulsed focused ultrasound (LFPFU) effectively improved the severity of arthritis in an arthritis mouse model established in DBA/1J mice. Additionally, we performed in-depth immune profiling of spleen samples from RA mice, RA mice that underwent ultrasound therapy, and healthy controls using mass cytometry along with extensive antibody panels and identified the immune composition of 14 cell populations, including CD4+/CD8+ T cells, B cells, natural killer cells, and dendritic cells. Moreover, multidimensional analysis according to cell-surface markers and phenotypes helped in identifying 4 and 5 cell subpopulations among T and myeloid cells, respectively, with 6 T cell subsets and 3 myeloid cell subsets responsive to ultrasound therapy among the 3 groups. Of these cell subsets, CD8+ T cell subsets showed a unique response to ultrasound stimulation in RA mice. Specifically, CD8+ T cells show a noticeable correlation with the degree of arthritis progression and could serve as an indicator for spleen-focused ultrasound-based therapy. Furthermore, single-cell RNA sequencing of spleen cells revealed the importance of T, B, and myeloid cell populations in the anti-inflammatory pathway. These results elucidated the unique cell subsets and transcriptome of splenic cells responsive to LFPFU and demonstrated the potential of spleen-focused ultrasound stimulation in the treatment of inflammatory diseases.

In Vitro and In Vivo Anti-Arthritic Potential of Caralluma tuberculata N. E. Brown. and Its Chemical Characterization

Present research was planned to assess the in vitro and in vivo anti-arthritic potential of Caralluma tuberculata N. E. Brown. methanolic (CTME) and aqueous (CTAQ) extracts. Chemical characterization was done by high-performance liquid chromatography and gas chromatography−mass spectrometry analysis. The Complete Freund’s Adjuvant (CFA) was injected in left hind paw of rat at day 1 and dosing at 150, 300 and 600 mg/kg was started on the 8th day via oral gavage in all groups except normal and disease control rats (which were given distilled water), whereas methotrexate (intraperitoneal; 1 mg/kg/mL) was administered to standard control. The CTME and CTAQ exerted significant (p < 0.01−0.0001) in vitro anti-arthritic action. Both extracts notably reduced paw edema, and restored weight loss, immune organs weight, arthritic score, RBCs, ESR, platelet count, rheumatoid factor (RF), C-reactive protein, and WBCs in treated rats. The plant extracts showed significant (p < 0.05−0.0001) downregulation of tumor necrosis factor-α, Interleukin-6, -1β, NF-κB, and cyclooxygenase-2, while notably upregulated IL-4, IL-10, I-κBα in contrast to disease control rats. The plant extracts noticeably (p < 0.001−0.0001) restored the superoxide dismutase and catalase activities and MDA levels in treated rats. Both extracts exhibited significant anti-arthritic potential. The promising potential was exhibited by both extracts probably due to phenolic, and flavonoids compounds.

Vitexin alleviates inflammation and enhances apoptosis through the regulation of the JAK/STAT/SOCS signaling pathway in the arthritis rat model

Rheumatoid arthritis (RA) is a chronic inflammatory and autoimmune disorder. RA is progressive and needs long-term treatment. Vitexin is a naturally-occurring flavonoid that is identified in various plant sources. Vitexin is demonstrated to produce antioxidant effects with numerous pharmacological activities. This experimental in vivo study assessed the antiarthritic and apoptotic role of a natural plant extract, vitexin, on RA. Collagen-induced arthritis (CIA) rat model Sprague Dawley males were grouped into five sets with six rats each: control, CIA, CIA + vitexin (10 mg/kg bw), CIA + Methotrexate (1 mg/kg bw), and vitexin (10 mg/kg bw) alone. The body weight, organ weight, biochemical assay, inflammatory enzymes, apoptosis, and cytokines levels were evaluated and compared among groups. Janus kinase (JAK)/signal transducer and activator of transcription (STAT)/suppressors of cytokine signaling (SOCS) levels and histopathology of ankle joints were also studied and compared. Significance was considered at a p < 0.05. Vitexin (10 mg/kg bw) significantly reduced the inflammatory enzyme markers, interleukin (IL)-1β, IL-6, IL-17, IL-4, IL-10, tumor necrosis factor-α, interferon-γ, and iNOS levels in arthritis rats (p < 0.05). Vitexin significantly improved collagen-induced arthritic histological changes (p < 0.05). Vitexin also reduced JAK/STAT expressions associated with inflammation and significantly increased elevated SOCS levels (p < 0.05). Aberration in apoptosis, inflammatory mediators, C-reactive protein, and rheumatoid factor levels in the arthritic rats reverted to normal with vitexin. These results emphasize that vitexin possesses anti-inflammatory and apoptotic activity via the regulation of JAK/STAT/SOCS signaling in CIA in a rat model. Hence, vitexin is a promising auxiliary drug for RA treatment.

Apoptotic vesicles ameliorate lupus and arthritis via phosphatidylserine-mediated modulation of T cell receptor signaling

Mesenchymal stem cells (MSCs) influence T cells in health, disease and therapy through messengers of intercellular communication including extracellular vesicles (EVs). Apoptosis is a mode of cell death that tends to promote immune tolerance, and a large number of apoptotic vesicles (apoVs) are generated from MSCs during apoptosis. In an effort to characterize these apoVs and explore their immunomodulatory potential, here we show that after replenishing them systemically, the apoV deficiency in Fas mutant mice and pathological lymphoproliferation were rescued, leading to the amelioration of inflammation and lupus activity. ApoVs directly interacted with CD4⁺ T cells and inhibited CD25 expression and IL-2 production in a dose-dependent manner. A broad range of Th1/2/17 subsets and cytokines including IFNγ, IL17A and IL-10 were suppressed while Foxp3⁺ cells were maintained. Mechanistically, exposed phosphatidylserine (PtdSer/PS) on apoVs mediated the interaction with T cells to disrupt proximal T cell receptor signaling transduction. Remarkably, administration of apoVs prevented Th17 differentiation and memory formation, and ameliorated inflammation and joint erosion in murine arthritis. Collectively, our findings unveil a previously unrecognized crosstalk between MSC apoVs and CD4⁺ T cells and suggest a promising therapeutic use of apoVs for autoimmune diseases.

Differential Contribution of NF-κB Signaling Pathways to CD4+ Memory T Cell Induced Activation of Endothelial Cells

Endothelial cells (ECs) are important contributors to inflammation in immune-mediated inflammatory diseases (IMIDs). In this study, we examined whether CD4⁺ memory T (T_m) cells can drive EC inflammatory responses. Human T_m cells produced ligands that induced inflammatory responses in human umbilical vein EC as exemplified by increased expression of inflammatory mediators including chemokines and adhesion molecules. NF-κB, a key regulator of EC activation, was induced by T_m cell ligands. We dissected the relative contribution of canonical and non-canonical NF-κB signaling to T_m induced EC responses using pharmacological small molecule inhibitors of IKKβ (iIKKβ) or NF-κB inducing kinase (iNIK). RNA sequencing revealed substantial overlap in IKKβ and NIK regulated genes (n=549) that were involved in inflammatory and immune responses, including cytokines (IL-1β, IL-6, GM-CSF) and chemokines (CXCL5, CXCL1). NIK regulated genes were more restricted, as 332 genes were uniquely affected by iNIK versus 749 genes by iIKKβ, the latter including genes involved in metabolism, proliferation and leukocyte adhesion (VCAM-1, ICAM-1). The functional importance of NIK and IKKβ in EC activation was confirmed by transendothelial migration assays with neutrophils, demonstrating stronger inhibitory effects of iIKKβ compared to iNIK. Importantly, iIKKβ – and to some extent iNIK - potentiated the effects of currently employed therapies for IMIDs, like JAK inhibitors and anti-IL-17 antibodies, on EC inflammatory responses. These data demonstrate that inhibition of NF-κB signaling results in modulation of T_m cell-induced EC responses and highlight the potential of small molecule NF-κB inhibitors as a novel treatment strategy to target EC inflammatory responses in IMIDs.

Peripheral distributions of IL-4-producing CD4 + T cells and CD4 + CD25 + FoxP3 + T cells (Tregs) in rheumatoid arthritis patients with poor response to therapy are associated with HLA shared epitope alleles and ACPA status

Specific profiling of CD4 + T cell subsets in the circulation and inflamed joints of rheumatoid arthritis (RA) patients may have therapeutic implications. This study aimed to evaluate the peripheral distributions of Th2 and Treg cells in relation to HLA-shared epitope (SE) alleles and anti-cyclic citrullinated peptide antibody (ACPAs) status in patients with good response (GR) and poor response (PR) to treatment. The frequencies of IL-4-producing CD4 + T cells (Th2) and CD4 + CD25 + Foxp3 + T cells (Tregs) were determined by flow cytometry in 167 RA patients including 114 GR and 53 PR cases. CD4 + T cell subsets were also analyzed based on HLA-SE and ACPAs statuses. One hundred nine of 167 patients were positives for HLA-SE, 63.4% for ACPAs, 43.7% for SE/ACPAs and 14.9% were negatives for SE/ACPAs. Higher frequencies of Th2 (P = 0.001) and Treg cells (P = 0.03) were found in the patients versus controls. Increased and decreased frequencies of Th2 and Tregs cells were observed in the PR versus GR patients respectively (P = 0.003 and P = 0.004). Higher proportions of Th2 cells were observed in the SE⁺RA versus SE^-RA (P = 0.001), in ACPA⁺RA versus ACPA^-RA (P = 0.005) and in the SE⁺ACPA⁺RA versus SE^-ACPA^-RA patients (P = 0.002). Treg cells frequencies decreased in the SE⁺RA versus SE^-RA (P = 0.03) and in SE⁺ACPA⁺RA versus SE^-ACPA^-RA (P = 0.02). ACPA⁺GR and SE⁺PR patients showed higher proportions of Th2 cells than ACPA^-GR and SE^-PR patients respectively (P = 0.02 and P = 0.01). Analysis of the CD4 + T cell subsets profiles in conjunction with genetic background and autoantibodies patterns can be useful for precise therapeutic response monitoring in the RA patients.

Emerging Roles of Mucosal-Associated Invariant T Cells in Rheumatology

Mucosal-associated invariant T (MAIT) cells are an unconventional T cell subset expressing a semi-invariant TCR and recognize microbial riboflavin metabolites presented by major histocompatibility complex class 1-related molecule (MR1). MAIT cells serve as innate-like T cells bridging innate and adaptive immunity, which have attracted increasing attention in recent years. The involvement of MAIT cells has been described in various infections, autoimmune diseases and malignancies. In this review, we first briefly introduce the biology of MAIT cells, and then summarize their roles in rheumatic diseases including systemic lupus erythematosus, rheumatoid arthritis, primary Sjögren’s syndrome, psoriatic arthritis, systemic sclerosis, vasculitis and dermatomyositis. An increased knowledge of MAIT cells will inform the development of novel biomarkers and therapeutic approaches in rheumatology.

Cell-specific epigenetic drivers of pathogenesis in rheumatoid arthritis

Rheumatoid arthritis is a complex, inflammatory autoimmune disease, which is characterized by pain, swelling and joint damage driven by the altered behavior of a number of different cell types such as synovial fibroblasts macrophages and lymphocytes. The mechanism underlying pathogenesis is unclear but increasing evidence points to altered epigenetic regulation within these cell types which promotes the activated destructive behavior that underlies disease pathogenesis. This review summarizes the key epigenetic modifications in the most important cells types in rheumatoid arthritis, which are associated with disease activity. We also discuss emerging avenues of research focusing on readers of epigenetic markers which may serve to be potential therapeutic targets.

Ethyl acetate extract of Tibetan medicine Rhamnella gilgitica ameliorated type II collagen-induced arthritis in rats via regulating JAK-STAT signaling pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Rhamnella gilgitica Mansf. et Melch. (སེང་ལྡེང་།, RG) is a traditional Tibetan medicinal plant that is currently grown throughout Tibet. According to the theory of Tibetan medicine, RG is efficient for removing rheumatism, reducing swelling, and relieving pain. Hence, it has been used for the treatment of rheumatoid arthritis (RA) in Tibet for many years. However, there are no previous reports on the anti-RA activities of ethyl acetate extract of RG (RGEA).

AIM OF THE STUDY

This study aimed to explore the anti-RA effect and mechanism of RGEA on collagen-induced arthritis (CIA) in rats.

MATERIALS AND METHODS

The CIA model was established in male Wister rats by intradermal injection of bovine type II collagen and Complete Freund's Adjuvant at the base of the tail and left sole, respectively. The rats were orally administered with RGEA (9.71, 19.43, or 38.85 mg/kg) for 23 days. The body weight, swelling volume, arthritis index score, thymus and spleen indices, and pathological changes were observed to evaluate the effect of RGEA on RA. Furthermore, the inflammatory cytokines in serum, such as interleukin1 beta (IL-1β), tumor necrosis factor alpha (TNF-α), interleukin6 (IL-6), interleukin17 (IL-17), interferon-γ (INF-γ), interleukin4 (IL-4), and interleukin10 (IL-10) were measured by enzyme linked immunosorbent assay (ELISA) to explore the anti-inflammatory effects of RGEA. The terminal deoxynucleotidyl transferase dUTP nick-end labelling (TUNEL) staining was used to examine apoptosis. Finally, the protein and gene expression of B-cell lymphoma-2-associated X (Bax), B-cell lymphoma 2 (Bcl-2), Caspase3, janus-activated kinase 2 (JAK2), signal transducer and activator of transcription 3 (STAT3), suppressor of cytokine signaling1 (SOCS1), and 3 (SOCS3) in synovial tissue were detected using immunohistochemistry and real-time quantitative polymerase chain reaction (RT-qPCR).

RESULTS

After the treatment with RGEA, the body weight of rats was restored, both the arthritis index and paw swelling were suppressed, and spleen and thymus indices were decreased. RGEA reduced the inflammatory cells and synovial hyperplasia in the synovial tissue of the knee joint, and suppressed bone erosion. Meanwhile, RGEA decreased the levels of IL-1β, IL-6, IL-17, TNF-α, and INF-γ, while increased the levels of IL-4 and IL-10. TUNEL fluorescence apoptosis results confirmed that RGEA obviously promoted the apoptosis of synovial cells. Further studies showed that RGEA inhibited the proteins and mRNAs expression of JAK2 and STAT3 as well as increased the proteins and mRNAs expression of SOCS1 and SOCS3. In addition, RGEA upregulated the expression of Bax and Caspase3, and downregulated the expression of Bcl-2.

CONCLUSION

The anti-RA effectof RGEA might be related to the promotion of apoptosis and inhibition of inflammation, which regulated the JAK-STAT pathway.

Decreased numbers and sex-based differences of circulating regulatory T cells in patients with seropositive undifferentiated arthritis

Aims:

CD4⁺ T cells play crucial roles as both mediators and regulators of the pathogenesis of rheumatoid arthritis (RA). However, the characteristics of CD4⁺ T cell subpopulations in the earliest stage of RA development remain unclear. Hence, we determined the proportions and absolute counts of circulating CD4⁺ T cell subsets in patients with seropositive undifferentiated arthritis (SUA), the early and preclinical stage of RA.

Methods:

Peripheral blood samples and clinical information were collected from 177 patients with SUA, 104 patients with RA, and 120 healthy controls. All patients were newly diagnosed and untreated. Proportions and absolute counts of CD4⁺ T cell subpopulations were determined by flow cytometric analysis.

Results:

In patients with SUA, percentages and absolute counts of circulating regulatory T (Treg) cells were decreased significantly and Th17/Treg cell ratios were abnormally increased, whereas Th17 cell numbers were similar to those in healthy controls. In addition, sex-based differences in circulating Treg cells were observed, with female SUA patients having lower proportions and absolute counts of Treg cells than those in males. Moreover, female patients with SUA had higher erythrocyte sedimentation rates and 28-joint Disease Activity Scores than those in males.

Conclusion:

Immune tolerance deficiency resulting from an abnormal reduction in circulating Treg cells might be the most crucial immunological event in the earliest stage of RA. The sex-specific disparity in Treg cells should also be considered for immunoregulatory and preventive strategies targeting early RA.

The significance of serum 14-3-3η level in rheumatoid arthritis patients

BACKGROUND

RA is a systemic inflammatory condition characterized by chronic arthritis and often associated with irreversible joint damage.

OBJECTIVES

To assess the significance of serum level of 14-3-3η in RA and its association with clinical and serological features of the disease.

METHODS

This is a case-control study done on 80 participants. They were divided into 2 groups. Group 1: 40 rheumatoid arthritis patients compared to group 2: 40 healthy participants matched for age and sex. Laboratory investigations including complete blood count (CBC), erythrocyte sedimentation rate (ESR), C-reactive protein (CRP) rheumatoid factor (RF), anti-citrullinated peptide antibodies (ACPAs), and serum 14-3-3η were done to all participants. Radiological examination in the form of plain X-ray for hands and feet was done to all patients.

RESULTS

Serum levels of 14-3-3η were significantly higher in RA patients compared to the control group (p < 0.001). Serum 14-3-3η was the only predictor of high Larsen's score (p = 0.013) on using linear regression analysis. Serum 14-3-3η can predict RA in healthy controls in univariate (p = 0.001) and multivariate (p = 0.004) analyses. The receiver operating characteristic (ROC) curve of 14-3-3η was constructed for discrimination between RA and control subjects. The best cut-off value was 61.9 ng/mL, with fair AUC (0.773, p < 0.001), 95% CI (0.656-0.889), and the sensitivity and specificity of 14-3-3η for RA diagnosis as 65% and 95% respectively. Also, we constructed ROC curves for RF, ACPA, 14-3-3η, and their combinations; we found that the highest test sensitivity of 95.7% appeared on adding the 3 markers together, and the highest test specificity of 100% was detected on adding RF to ACPA, 14-3-3η to ACPA or the 3 molecules together.

CONCLUSION

14-3-3η could be a valuable marker for the diagnosis of RA patients and it may have prognostic value. Key Points • 14-3-3η is a valuable marker for the diagnosis of RA patients. • 14-3-3η reflects disease severity and joint damage in RA patients.

Induced, but not natural, regulatory T cells retain phenotype and function following exposure to inflamed synovial fibroblasts

Aberrant number and/or dysfunction of CD4⁺Foxp3⁺ Regulatory T cells (T_regs) are associated with the pathogenesis of rheumatoid arthritis (RA). A previous study has demonstrated that thymus-derived, natural T_regs (nT_regs) prefer to accumulate in inflamed joints and transdifferentiate to T_H17 cells under the stimulation of inflamed synovial fibroblasts (SFs). In this study, we made a head-to-head comparison of both T_reg subsets and demonstrated that induced T_regs (iT_regs), but not nT_regs, retained Foxp3 expression and regulatory function on T effector cells (T_effs) after being primed with inflamed SFs. In addition, iT_regs inhibited proliferation, inflammatory cytokine production, migration, and invasion ability of collagen-induced arthritis (CIA)-SFs in vitro and in vivo. Moreover, we noted that iT_regs directly targeted inflamed SFs to treat autoimmune arthritis, while nT_regs failed to do this. Thus, manipulation of the iT_reg subset may have a greater potential for prevention or treatment of patients with RA.

Metabolic control of T cells in autoimmunity

PURPOSE OF REVIEW

Th1, Th17, and Treg cells play distinct roles in autoimmune diseases, including systemic lupus erythematosus, multiple sclerosis, and rheumatoid arthritis. During the last 5 years we have learned that T-cell metabolism affects cell survival, differentiation and fate of T cells.

RECENT FINDINGS

We highlight recent studies which have reported on T-cell metabolism in autoimmune diseases, differences in cellular metabolisms in T-cell subsets among various diseases and transcription factors which control the expression and function of central metabolic enzymes.

SUMMARY

Distinct metabolic processes control the function of T-cell subsets in autoimmune disease and known transcription factors control the activity of metabolic enzymes. The revealed insights into the metabolic events of immune cells offer opportunities for new therapeutic approaches.

Semaphorin 4D Induces an Imbalance of Th17/Treg Cells by Activating the Aryl Hydrocarbon Receptor in Ankylosing Spondylitis

Objectives

Semaphorin 4D (Sema4D) is constitutively expressed on T cells and osteoclasts, and regulates T cell proliferation and bone remodeling. In addition, several studies have shown that Sema4D is involved in the pathogenesis of autoimmunity. We undertook this study to investigate the mechanism by which Sema4D affects the pathogenic progress of ankylosing spondylitis (AS).

Methods

Soluble Sema4D (sSema4D) levels in serum were analyzed by enzyme-linked immunosorbent assay. The cell surface levels and transcripts of Sema4D were evaluated in CD4 + and CD19 + cells from the AS patients and healthy individuals. The mRNA expression levels were assessed by quantitative polymerase chain reaction (qPCR). The proportions of Treg cells and IL-17-producing T-cells (Th17 cells) differentiated from CD4 + T cells were analyzed by flow cytometric analysis. The aryl hydrocarbon receptor (AhR) agonistic effect of Sema4D was detected by analyzing the activation of downstream signaling pathways and target genes using Luciferase and EROD assay.

Results

Levels of sSema4D were elevated in both serum from AS patients, and clinical features markers were correlated with serum sSema4D levels. Sema4D facilitated CD4 + T cells proliferation and Th17 cells differentiation and inhibited Treg cells differentiation by enhancing RORγt expression and reducing Foxp3 expression, with increasing expression and secretion of IL-17 and IL-22. It induced the expression and activity of AhR target gene CYP1A1 and XRE reporter activity via interaction with CD72.

Conclusion

These findings indicate that Sema4D as a potent activator of T cells in the immune response contributes to the inflammation of AS by inducing imbalance in Th17 and Treg cell populations in an AhR-dependent manner, suggesting it is a crucial participant in AS pathogenesis.

Hypoxia decreases the T helper cell-suppressive capacity of synovial fibroblasts by downregulating IDO1-mediated tryptophan metabolism

OBJECTIVE

The development of RA is linked to local infiltration of immune cells and to changes in the phenotype of synovial fibroblasts. Synovial fibroblasts possess the capacity to suppress T cell responses through indoleamine 2, 3-dioxygenase 1 (IDO1)-mediated tryptophan metabolism. However, synovial fibroblasts from RA patients are restricted in this immune-modulatory function. Moreover, hypoxic conditions are detected within synovial tissues of RA patients, with oxygen tensions of only 3.2% O2. This study aims at investigating the effects of hypoxia on the interaction between T cells and synovial fibroblasts, particularly on the T cell-suppressive capacities of synovial fibroblasts.

METHODS

Synovial fibroblasts were cultured with Th cells under normoxic and hypoxic conditions (3% O2). Th cell proliferation was detected by flow cytometry. Tryptophan and kynurenine amounts were measured by HPLC. IDO1 expression and signal transducer and activator of transcription 1 (STAT1) phosphorylation were quantified by real-time PCR or western blot, and cytokine secretion by ELISA.

RESULTS

Hypoxic conditions strongly diminished the Th cell-suppressive capacities of both OA synovial fibroblasts and RA synovial fibroblasts. Accordingly, IDO1 mRNA and protein expression, STAT1 phosphorylation and tryptophan metabolism were greatly reduced in OA synovial fibroblasts by hypoxia. MMP-3, IL-6, IL-10 and IFNγ secretion were significantly decreased under hypoxia in synovial fibroblast-Th cell co-cultures, while IL-17A levels were elevated. Supplementation with IFNγ, a well-known inducer of IDO1 expression, could rescue neither IDO1 expression nor Th cell suppression under hypoxic conditions.

CONCLUSION

Hypoxia strongly affected the crosstalk between synovial fibroblasts and Th cells. By reducing the efficiency of synovial fibroblasts to restrict Th cell proliferation and by increasing the expression of IL-17A, hypoxia might have implications on the pathophysiology of RA.

IgD-Fc-Ig fusion protein, a new biological agent, inhibits T cell function in CIA rats by inhibiting IgD-IgDR-Lck-NF-κB signaling pathways

IgD-Fc-Ig fusion protein, a new biological agent, is constructed by linking a segment of human IgD-Fc with a segment of human IgG1-Fc, which specifically blocks the IgD-IgDR pathway and selectively inhibits the abnormal proliferation, activation, and differentiation of T cells. In this study we investigated whether IgD-Fc-Ig exerted therapeutic effects in collagen-induced arthritis (CIA) rats. CIA rats were treated with IgD-Fc-Ig (1, 3, and 9 mg/kg) or injected with biological agents etanercept (3 mg/kg) once every 3 days for 40 days. In the PBMCs and spleen lymphocytes of CIA rats, both T and B cells exhibited abnormal proliferation; the percentages of CD3⁺ total T cells, CD3⁺CD4⁺ Th cells, CD3⁺CD4⁺CD25⁺-activated Th cells, Th1(CD4⁺IFN-γ⁺), and Th17(CD4⁺IL-17⁺) were significantly increased, whereas the Treg (CD4⁺CD25⁺Foxp3⁺) cell percentage was decreased. IgD-Fc-Ig administration dose-dependently decreased the indicators of arthritis; alleviated the histopathology of spleen and joint; reduced serum inflammatory cytokines levels; decreased the percentages of CD3⁺ total T cells, CD3⁺CD4⁺ Th cells, CD3⁺CD4⁺CD25⁺-activated Th cells, Th1 (CD4⁺IFN-γ⁺), and Th17(CD4⁺IL-17⁺); increased Treg (CD4⁺CD25⁺Foxp3⁺) cell percentage; and down-regulated the expression of key molecules in IgD-IgDR-Lck-NF-κB signaling (p-Lck, p-ZAP70, p-P38, p-NF-κB65). Treatment of normal T cells with IgD (9 μg/mL) in vitro promoted their proliferation. Co-treatment with IgD-Fc-Ig (0.1–10 μg/mL) dose-dependently decreased IgD-stimulated T cell subsets percentages and down-regulated the IgD-IgDR-Lck-NF-κB signaling. In summary, this study demonstrates that IgD-Fc-Ig alleviates CIA and regulates the functions of T cells through inhibiting IgD-IgDR-Lck-NF-κB signaling.

Evaluation of plasma cytokine protein array profile: the highlighted PDGF-BB in rheumatoid arthritis

OBJECTIVES

The cytokines play critical roles in the complex pathogenesis of rheumatoid arthritis (RA), but the specific cytokines are still in need of being discovered. This multi-stage study was performed to identify novel RA cytokines in plasma and further understand the pathological mechanism of the identified cytokines.

METHOD

The plasma cytokine protein profile was evaluated by using Human Cytokine Antibody Array 440 in 18 subjects (RA: healthy control = 9:9). Then, enzyme-linked immunosorbent assay (ELISA) was used to validate the highlighted cytokines in 80 subjects (RA: healthy control = 40:40). Further functional experiments on fibroblast-like synoviocytes were performed to identify the pathological mechanisms of the highlighted cytokines for RA.

RESULTS

A total of seven significant cytokines have differential expressions between RA patients and controls (fold change (FC) > 2, P value < 0.05). The difference in plasma for the highlighted platelet-derived growth factor (PDGF)-BB was validated in an independent validation sample (P = 0.005). Further, the PDGF-BB obviously promotes cell proliferation of MH7A cell, probably by inhibiting cell apoptosis and accelerating the cell cycle. The PDGF-BB can also promote MH7A cell migration.

CONCLUSIONS

This study evaluated the plasma cytokine protein array profile associated with RA and highlighted the importance of PDGF-BB. PDGF-BB has an important role in RA-FLS proliferation and migration. These results suggest that PDGF-BB might contribute to occurrence and development of RA. Key Points • The levels of plasma cytokines were systemically tested using Human Cytokine Antibody Arrays. • The expression difference of PDGF-BB was validated in an independent sample. • PDGF-BB obviously promotes cell proliferation and migration in RA-FLS.

The effects of long non-coding ribonucleic acids on various cellular components in rheumatoid arthritis

RA is a chronic, autoimmune-mediated inflammatory pathology. Long non-coding RNAs (lncRNAs) are a novel group of non-coding RNAs with a length of >200 nucleotides. There are reports emerging that suggest that lncRNAs participate in establishing and sustaining autoimmune diseases, including RA. In this review article, we highlight the functions of lncRNAs in different cell types in RA. Our review indicates that lncRNAs affect various cellular components and are novel candidates that could constitute promising targets for the diagnosis and treatment of RA.

The role of myeloid-derived suppressor cells in the pathogenesis of rheumatoid arthritis; anti- or pro-inflammatory cells?

Myeloid-derived suppressor cells (MDSCs) are a heterogeneous group of the immature myeloid cells that are derived from the myeloid progenitors with immunosuppressive functions. MDSCs are accumulated in the inflammatory sites during some autoimmune disorders, such as rheumatoid arthritis (RA) and can be an important factor in the pathogenesis of these diseases. Some research has shown the anti-inflammatory role of MDSCs during the RA progression and supports the hypothesis that MDSCs can be a potential treatment option for autoimmunity with their immunosuppressive activity. In contrast, some papers have reported the opposite effects of MDSCs, and support the hypothesis that MDSCs have a pro-inflammatory role in autoimmune disease. MDSCs functions in RA have not been fully understood, and some controversies, as well as many unanswered questions, remain. Although the two well-known subgroups of MDSCs, M-MDSC, and PMN-MDSC, seem to have different suppressive functions and regulate the immune system responses in a different manner; some studies have shown these cells are converted to each other and even to other cells under different pathological conditions. This review summarises some of the latest papers with respect to the MDSCs functions and discusses the relationship between MDSCs and inflammation in the context of rheumatoid arthritis.

The Proportion of Regulatory T Cells in Patients with Ankylosing Spondylitis: A Meta-Analysis

OBJECTIVE

Accumulating evidence indicates that regulatory T cells (Tregs) may be involved in the pathogenesis of ankylosing spondylitis (AS). As different markers have been used to identify Tregs, some studies on the proportions of Tregs in AS patients have generated considerable controversy. To clarify the status of Tregs in such patients, we determine the proportion changes of peripheral Tregs during development of the disease, with different cellular markers.

METHODS

We systematically searched Embase, PubMed, Cochrane, Web of Knowledge, FDA.gov, and Clinical Trials.gov for the studies reporting the proportion of Tregs in AS patients. Using the PRISMA guidelines, we performed a random-effects meta-analysis of the frequencies of peripheral Tregs defined in different ways. Inconsistency was evaluated using the I-squared index (I 2), and publication bias was assessed by examining funnel plot asymmetry using the Begger and Egger tests.

RESULTS

A total 29 studies involving 1732 participants were included in the meta-analysis. Their conclusions of using the diversity of Tregs surface markers were inconsistent with each other. No significant difference in the proportions of Tregs was evident regardless of the definitions used [-0.709, (-1.455, 0.037, p = 0.063), I 2 = 97.3%]. Six studies used "single CD25-positive" cells as Tregs, which revealed a significant increase in AS patients compared with healthy blood donors [0.736, (0.138, 1.334), p = 0.016, I 2 = 80.7%]. Notably, the proportions of "CD4+CD25+FOXP3+," "CD4+CD25highCD127low/-," or "CD4+CD25+CD127low" T cells were lower in AS patients [-2.856, (-4.645, -1.066), p = 0.002; -1.812, (-2.648, -0.977), p < 0.001; -1.12, (-1.605, -0.635), p < 0.001]. Tregs defined as "CD25high," "CD25bright," "CD25bright/highCD127low/-," "CD4+FOXP3+," "CD4+CD25highFOXP3+," and "CD4+CD25+CD127-" did not differ in proportion between AS patients and healthy blood donors.

CONCLUSIONS

The levels of Tregs varied based on the cellular identification markers used. The proportions of CD4+CD25+FOXP3+Tregs, CD4+CD25highCD127low/-, or CD4+CD25+CD127low in blood of AS patients were significantly decreased as compared with those in healthy blood donors, and our findings lend support to the idea that the Treg status of AS patients is important. And we recommend the above as the best definition of Tregs when evaluating the status of such patients.

Mixed-effects association of single cells identifies an expanded effector CD4+ T cell subset in rheumatoid arthritis

High-dimensional single-cell analyses have improved the ability to resolve complex mixtures of cells from human disease samples; however, identifying disease-associated cell types or cell states in patient samples remains challenging because of technical and interindividual variation. Here, we present mixed-effects modeling of associations of single cells (MASC), a reverse single-cell association strategy for testing whether case-control status influences the membership of single cells in any of multiple cellular subsets while accounting for technical confounders and biological variation. Applying MASC to mass cytometry analyses of CD4⁺ T cells from the blood of rheumatoid arthritis (RA) patients and controls revealed a significantly expanded population of CD4⁺ T cells, identified as CD27^- HLA-DR⁺ effector memory cells, in RA patients (odds ratio, 1.7; P = 1.1 × 10^-3). The frequency of CD27^- HLA-DR⁺ cells was similarly elevated in blood samples from a second RA patient cohort, and CD27^- HLA-DR⁺ cell frequency decreased in RA patients who responded to immunosuppressive therapy. Mass cytometry and flow cytometry analyses indicated that CD27^- HLA-DR⁺ cells were associated with RA (meta-analysis P = 2.3 × 10^-4). Compared to peripheral blood, synovial fluid and synovial tissue samples from RA patients contained about fivefold higher frequencies of CD27^- HLA-DR⁺ cells, which comprised ~10% of synovial CD4⁺ T cells. CD27^- HLA-DR⁺ cells expressed a distinctive effector memory transcriptomic program with T helper 1 (T_H1)- and cytotoxicity-associated features and produced abundant interferon-γ (IFN-γ) and granzyme A protein upon stimulation. We propose that MASC is a broadly applicable method to identify disease-associated cell populations in high-dimensional single-cell data.

Defining inflammatory cell states in rheumatoid arthritis joint synovial tissues by integrating single-cell transcriptomics and mass cytometry

To define the cell populations that drive joint inflammation in rheumatoid arthritis (RA), we applied single-cell RNA sequencing (scRNA-seq), mass cytometry, bulk RNA sequencing (RNA-seq) and flow cytometry to T cells, B cells, monocytes, and fibroblasts from 51 samples of synovial tissue from patients with RA or osteoarthritis (OA). Utilizing an integrated strategy based on canonical correlation analysis of 5,265 scRNA-seq profiles, we identified 18 unique cell populations. Combining mass cytometry and transcriptomics revealed cell states expanded in RA synovia: THY1(CD90)+HLA-DRAhi sublining fibroblasts, IL1B+ pro-inflammatory monocytes, ITGAX+TBX21+ autoimmune-associated B cells and PDCD1+ peripheral helper T (TPH) cells and follicular helper T (TFH) cells. We defined distinct subsets of CD8+ T cells characterized by GZMK+, GZMB+, and GNLY+ phenotypes. We mapped inflammatory mediators to their source cell populations; for example, we attributed IL6 expression to THY1+HLA-DRAhi fibroblasts and IL1B production to pro-inflammatory monocytes. These populations are potentially key mediators of RA pathogenesis.

[Role of erythroblast-like Ter cells in the pathogenesis of collagen-induced arthritis]

OBJECTIVE

To explore the role of Ter cells in the development of the collagen-induced arthritis (CIA), we detected their quantity changes in the spleen of different stages of CIA mice and analyzed the correlation between Ter cells and the joint scores, and we also analyzed the correlation between Ter cells and the frequencies of T and B cell subsets, so as to further understand the pathogenesis of rheumatoid arthritis.

METHODS

The six to eight weeks DBA/1 mice were used to prepare CIA model. After the second immunization, we began to evaluate the joint score. According to the time of CIA onset and the joint score, the CIA mice were divided into three stages: early, peak and late stages. According to the final joint score, the CIA mice at the peak stage were subdivided into the high score group (score>8) and the low score group (score≤8). The frequencies of Ter cells in the spleen of the naïve mice and the CIA mice at various stages and the frequencies of T and B cell subsets in the spleen of the CIA mice at the peak stage were detected by flow cytometry, then we carried on the correlation analysis.

RESULTS

The frequencies of Ter cells in the spleen of the CIA mice was significantly higher than those of the naïve mice (8.522%±2.645% vs. 1.937%±0.725%, P<0.01), the frequencies of Ter cells in the spleen of the high score group mice was significantly lower than those of the low score group (6.217%±0.841% vs. 10.827%±0.917%, P<0.01). The frequencies of Th1 cells in the spleen of the high score group mice was significantly higher than those of the low score group mice (1.337%±0.110% vs. 0.727%±0.223%, P<0.05). The frequencies of Th17 cells in the spleen of the high score group mice was higher than those of the low score group mice (0.750%±0.171% vs. 0.477%±0.051%, P=0.099). The frequencies of germinal center B cells in the spleen of the high score group mice was significantly higher than those of the low score group mice (1.243%±0.057% vs. 1.097%±0.015%, P<0.05). Correlation analysis results showed that the frequencies of Ter cells in the spleen of the CIA mice at the peak stage was strongly negatively correlated with the frequencies of CD4+ T, Th1, Th17, and germinal center B cells, and was strongly positively correlated with the frequencies of B10 cells, indicating that these cells might have a protective effect in CIA. Studies on dynamic changes showed that the frequencies of Ter cells in the spleen of the CIA mice at the late stage was significantly lower than those at the peak stage (0.917%±0.588% vs. 8.522%±2.645%, P<0.001), suggesting the protective effect of these cells in arthritis.

CONCLUSION

Ter cells were significantly increased in the spleen of the CIA mice at peak stage, and were negatively correlated with joint scores and pathogenic immune cells, and positively correlated with protective immune cells. Ter cells were significantly decreased in the spleen of the CIA mice at the late stage. What we mentioned above suggests that Ter cells might be involved in the progression of rheumatoid arthritis as an immunomodulatory cell,but further in vivo and in vitro experiments are needed to verify its specific effects and mechanism.

T cell receptor β repertoires as novel diagnostic markers for systemic lupus erythematosus and rheumatoid arthritis

Objective

T cell receptor (TCR) diversity determines the autoimmune responses in systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA) and is closely associated with autoimmune diseases prognosis and prevention. However, the characteristics of variations in TCR diversity and their clinical significance is still unknown. Large series of patients must be studied in order to elucidate the effects of these variations.

Methods

Peripheral blood from 877 SLE patients, 206 RA patients and 439 healthy controls (HC) were amplified for the TCR repertoire and sequenced using a high-throughput sequencer. We have developed a statistical model to identify disease-associated TCR clones and diagnose autoimmune diseases.

Results

Significant differences were identified in variable (V), joining (J) and V-J pairing between the SLE or RA and HC groups. These differences can be utilised to discriminate the three groups with perfect accuracy (V: area under receiver operating curve > 0.99). One hundred ninety-eight SLE-associated and 53 RA-associated TCRs were identified and used for diseases classification by cross validation with high specificity and sensitivity. Disease-associated clones showed common features and high similarity between both autoimmune diseases. SLE displayed higher TCR heterogeneity than RA with several organ specific properties. Furthermore, the association between clonal expansion and the concentration of disease-associated clones with disease severity were identified, and pathogen-related TCRs were enriched in both diseases.

Conclusions

These characteristics of the TCR repertoire, particularly the disease-associated clones, can potentially serve as biomarkers and provide novel insights for disease status and therapeutical targets in autoimmune diseases.

Shedding New Light on The Role of ανβ3 and α5β1 Integrins in Rheumatoid Arthritis

ανβ3 and α5β1 are essential glycoproteins involved in the pathogenesis of rheumatoid arthritis (RA). Understanding of the role these integrins play in disease have been analyzed via description of cells-expressing ανβ3 and α5β1 and their mediators to trigger inflammation. ανβ3 and α5β1 facilitate cells-ECM and cell-cell communication, producing pro-inflammatory factors. Pro-inflammatory factors are essential for the building of undesirable new blood vessels termed angiogenesis which can further lead to destruction of bones and joints. Despite many attempts to target these glycoproteins, there are still some problems, therefore, there is still interest in understanding the synergistic role these integrins play in the pathogenesis of RA. The purpose of this review is to gain insights into the biological effects of ανβ3 and α5β1 in synovial tissues that are relevant to pathogenesis and therapy of RA.

Acute Pulmonary Hypertension Crisis after Adalimumab Reduction in Rheumatoid Vasculitis

Rheumatoid vasculitis is a rare etiology for pulmonary hypertension (PH) in patients with connective tissue disease. We encountered a case of acute PH crisis in a case with rheumatoid vasculitis eight months after undergoing adalimumab reduction. Since no repetition of arthralgia occurred after the adalimumab reduction, we decided to not increase the dose of adalimumab. However, hemodynamic collapse thereafter developed and even though steroid pulse therapy was administered, the patient nevertheless died. The autopsy showed clusters of acute and chronic inflammation around the remodeled pulmonary arteries along with micro-thrombi in the vessel lumen. We should consider the possibility of critical worsening of PH as a phenotype of vasculitis related to immunosuppressive therapy reduction.

The regulatory roles of glycosphingolipid-enriched lipid rafts in immune systems

Lipid rafts formed by glycosphingolipids (GSLs) on cellular membranes play important roles in innate and adaptive immunity. Lactosylceramide (LacCer) forms lipid rafts on plasma and granular membranes of human neutrophils. These LacCer-enriched lipid rafts bind directly to pathogenic components, such as pathogenic fungi-derived β-glucan and Mycobacteria-derived lipoarabinomannan via carbohydrate-carbohydrate interactions, and mediate innate immune responses to these pathogens. In contrast, a-series and o-series gangliosides form distinct rafts on CD4⁺ and CD8⁺ T cell subsets, respectively, contributing to the respective functions of these cells and stimulating adaptive immune responses through T cell receptors. These findings suggest that gangliosides play indispensable roles in T cell selection and activation. This Review introduces the involvement of GSL-enriched lipid rafts in innate and adaptive immunity.

Imbalance between T helper 17 and regulatory T cell subsets plays a significant role in the pathogenesis of systemic sclerosis

Systemic sclerosis (SSc) is a rare autoimmune disease that is characterized by fibrosis, inflammation, and vasculopathy of the skin and internal organs. The etiopathogenesis of SSc remains unclear. However, the pivotal role of T lymphocytes with an aberrant immune response in SSc is well established. Among T cells, IL-17-producing helper T (Th17) cell and regulatory T (Treg) cell subsets have recently been found to play crucial roles in SSc pathogenesis. Generally speaking, Th17 cell subsets up-regulate inflammation, fibrosis, and autoimmunity, which are present in SSc, while Treg cell subsets have an immunosuppressive function and resist the immunological performance of Th17 cells. Up-to-date evidence has pointed out that the imbalance and abnormal functions of Th17/Treg cells may contribute to SSc. Therefore, this review aims to summarize the current understanding of the vital cytokines and signaling pathways that are involved in Th17/Treg differentiation and functions, and their roles in the pathogenesis of SSc, thus providing novel insights about targeting the Th17/Treg balance as a potential therapy for SSc treatment in the near future.

Nur77 serves as a molecular brake of the metabolic switch during T cell activation to restrict autoimmunity

T cells critically depend on reprogramming of metabolic signatures to meet the bioenergetic demands during activation and clonal expansion. Here we identify the transcription factor Nur77 as a cell-intrinsic modulator of T cell activation. Nur77-deficient T cells are highly proliferative, and lack of Nur77 is associated with enhanced T cell activation and increased susceptibility for T cell-mediated inflammatory diseases, such as CNS autoimmunity, allergic contact dermatitis and collagen-induced arthritis. Importantly, Nur77 serves as key regulator of energy metabolism in T cells, restricting mitochondrial respiration and glycolysis and controlling switching between different energy pathways. Transcriptional network analysis revealed that Nur77 modulates the expression of metabolic genes, most likely in close interaction with other transcription factors, especially estrogen-related receptor α. In summary, we identify Nur77 as a transcriptional regulator of T cell metabolism, which elevates the threshold for T cell activation and confers protection in different T cell-mediated inflammatory diseases.

The Role of Long Non-coding RNAs in the Pathogenesis of RA, SLE, and SS

Rheumatoid diseases are a group of systemic autoimmune diseases which affect multiple organs with largely unknown etiology. In the past decade, long non-coding RNAs (lncRNAs) have emerged as important regulators of biological processes and contribute deeply to immune cell development and immune responses. Substantial evidences have been accumulated showing that LncRNAs involved in the pathogenesis of the rheumatoid diseases, including rheumatoid arthritis (RA), systemic lupus erythematosus (SLE) and Sjögren's syndrome (SS). In this review, we summarize literature combined with bioinformatics methods to analyze the unique and common lncRNAs patterns in rheumatoid diseases and try to reveal the important function of lncRNAs in RA, SLE and SS.

Metabolomic profile of systemic sclerosis patients

Systemic sclerosis (SSc) is an autoimmune disease of unknown aetiology characterized by vascular lesions, immunological alterations and diffuse fibrosis of the skin and internal organs. Since recent evidence suggests that there is a link between metabolomics and immune mediated disease, serum metabolic profile of SSc patients and healthy controls was investigated by ¹H-NMR and GC-MS techniques. The results indicated a lower level of aspartate, alanine, choline, glutamate, and glutarate in SSc patients compared with healthy controls. Moreover, comparing patients affected by limited SSc (lcSSc) and diffuse SSc (dcSSc), 6 discriminant metabolites were identified. The multivariate analysis performed using all the metabolites significantly different revealed glycolysis, gluconeogenesis, energetic pathways, glutamate metabolism, degradation of ketone bodies and pyruvate metabolism as the most important networks. Aspartate, alanine and citrate yielded a high area under receiver-operating characteristic (ROC) curves (AUC of 0.81; CI 0.726–0.93) for discriminating SSc patients from controls, whereas ROC curve generated with acetate, fructose, glutamate, glutamine, glycerol and glutarate (AUC of 0.84; CI 0.7–0.98) discriminated between lcSSc and dcSSc. These results indicated that serum NMR-based metabolomics profiling method is sensitive and specific enough to distinguish SSc from healthy controls and provided a feasible diagnostic tool for the diagnosis and classification of the disease.

Interleukin-10 produced by myeloid-derived suppressor cells is critical for the induction of Tregs and attenuation of rheumatoid inflammation in mice

Myeloid-derived suppressor cells (MDSCs) are heterogenous populations of immature myeloid progenitor cells with immunoregulatory function. MDSCs play critical roles in controlling the processes of autoimmunity but their roles in rheumatoid arthritis (RA) are controversial. The present study was undertaken to investigate whether MDSCs have therapeutic impact in mice with collagen-induced arthritis (CIA), an animal model of RA. We also examined the mechanisms underlying the anti-arthritic effect of MDSCs. In vitro treatment with MDSCs repressed IL-17 but increased FOXP3 in CD4+ T cells in mice. In vivo infusion of MDSCs markedly ameliorated inflammatory arthritis. Th17 cells and Th1 cells were decreased while Tregs were increased in the spleens of MDSCs-treated mice. MDSCs profoundly inhibited T cell proliferation. Addition of anti-IL-10 almost completely blocked the anti-proliferative effects of MDSCs on T cells. Anti-IL-10 blocked the expansion of Tregs by MDSCs. However, infusion of MDSCs from IL-10 KO mice failed to suppress inflammatory arthritis. MDSCs could reciprocally regulate Th17/Treg cells and suppress CIA via IL-10, suggesting that MDSCs might be a promising therapeutic strategy for T cell mediated autoimmune diseases including RA.

Silibinin alleviates inflammation and induces apoptosis in human rheumatoid arthritis fibroblast-like synoviocytes and has a therapeutic effect on arthritis in rats

Silibinin, a natural polyphenolic flavonoid, possesses anti-oxidant, anti-inflammation and anti-cancer properties. The present study was designed to investigate the effects of silibinin on rheumatoid arthritis (RA) pathogenesis-related cells and collagen-induced arthritis (CIA) and further explore the potential underlying mechanisms. Our results showed that silibinin suppressed cell viability and increased the percentage of apoptotic RA-fibroblast-like synoviocytes (FLS). Furthermore, the production of inflammatory cytokines in RA-FLS and a CIA rat model was effectively inhibited by silibinin. Silibinin also induced macrophage M2 polarization in RAW264.7 cells. We further demonstrated that silibinin inhibits Th17 cell differentiation in vitro. The nuclear factor kappa B (NF-κB) pathway was suppressed in RA-FLS. In addition, Sirtuin1 (SIRT1) was decreased after silibinin treatment, and RA-FLS transfection with a short hairpin RNA (shRNA) of SIRT1 enhanced silibinin-induced apoptosis. Autophagy was markedly decreased in a dose-dependent manner following silibinin treatment. These findings indicate that silibinin inhibited inflammation by inhibiting the NF-κB pathway, and SIRT1 may participate in silibinin-induced apoptosis. Silibinin also inhibited autophagy in RA-FLS. Thus, silibinin may be a potential therapeutic agent for the treatment of RA.

Biology of GM3 Ganglioside

Since the successful molecular cloning in 1998 of GM3 synthase (GM3S, ST3GAL5), the enzyme responsible for initiating biosynthesis of all complex gangliosides, the efforts of our research group have been focused on clarifying the physiological and pathological implications of gangliosides, particularly GM3. We have identified isoforms of GM3S proteins having distinctive lengths of N-terminal cytoplasmic tails, and found that these cytoplasmic tails define subcellular localization, stability, and in vivo activity of GM3S isoforms. Our studies of the molecular pathogenesis of type 2 diabetes, focused on interaction between insulin receptor and GM3 in membrane microdomains, led to a novel concept: type 2 diabetes and certain other lifestyle-related diseases are membrane microdomain disorders resulting from aberrant expression of gangliosides. This concept has enhanced our understanding of the pathophysiological roles of GM3 and related gangliosides in various diseases involving chronic inflammation, such as insulin resistance, leptin resistance, and T-cell function and immune disorders (e.g., allergic asthma). We also demonstrated an essential role of GM3 in murine and human auditory systems; a common pathological feature of GM3S deficiency is deafness. This is the first direct link reported between gangliosides and auditory functions.

Influence of NKG2D Genetic Variants on Response to Anti-TNF Agents in Patients with Rheumatoid Arthritis

A natural killer group 2 member D (NKG2D) acts as a powerful activating and co-stimulatory receptor on immune effector cells including NK and T cells. Disruptions within the NKG2D signalling pathway may trigger an exacerbated immune response and promote autoimmune reactions. The objective of the study was to evaluate a plausible role of polymorphisms within the NKG2D gene as a predictor of how effective anti-tumor necrosis factor (TNF) therapy is in rheumatoid arthritis (RA) patients. A total of 280 RA patients receiving anti-TNF therapy were genotyped for NKG2D rs2255336 (A > G), rs1049174 (C > G), and rs1154831 (C > A). Clinical response was evaluated according to the European League against Rheumatism (EULAR) criteria at the 12th and 24th week. Both the NKG2D rs225336 and rs1049174 polymorphisms were significantly associated with efficacy of TNF inhibitors. Inefficient therapy was more frequently observed in patients with rs2255336 GG or rs1049174 CC genotype as compared to other genotypes (p-value = 0.003 and p-value = 0.004, respectively). The presence of the rs2255336 G or the rs1049174 C allele correlated with a worse EULAR response (p-value = 0.002, p-value = 0.031, respectively). Moreover, patients carrying the rs2255336 or rs1049174 heterozygous genotype achieved better EULAR responses than patients with homozygous genotypes (p-value = 0.010 and p-value = 0.002, respectively). Data from the present study provides evidence that NKG2D polymorphisms may affect response to anti-TNF inhibitors in RA patients.

Leveraging blood and tissue CD4+ T cell heterogeneity at the single cell level to identify mechanisms of disease in rheumatoid arthritis

CD4+ T cells have been long known to play an important role in the pathogenesis of rheumatoid arthritis (RA), but the specific cell populations and states that drive the disease have been challenging to identify with low dimensional single cell data and bulk assays. The advent of high dimensional single cell technologies-like single cell RNA-seq or mass cytometry-has offered promise to defining key populations, but brings new methodological and statistical challenges. Recent single cell profiling studies have revealed a broad diversity of cell types among CD4+ T cells, identifying novel populations that are expanded or altered in RA. Here, we will review recent findings on CD4+ T cell heterogeneity and RA that have come from single cell profiling studies and discuss the best practices for conducting these studies.

Postmenopausal osteoporosis in rheumatoid arthritis: The estrogen deficiency-immune mechanisms link

Rheumatoid arthritis (RA) is characterized, among other factors, by systemic bone loss, reaching ~50% prevalence of osteoporosis in postmenopausal women. This is roughly a doubled prevalence in comparison with age-matched non-RA women. Postmenopausal RA women are more likely to be sero-positive for the anti-citrullinated peptide antibody (ACPA). Our extensive review of recent scientific literature enabled us to propose several mechanisms as responsible for the accelerated bone loss in ACPA(+) RA postmenopausal women. Menopause-associated estrogen deficiency plays a major role in these pathological mechanisms, as follows.

Immunomodulation of autoimmune arthritis by pro-inflammatory cytokines

Pro-inflammatory cytokines promote autoimmune inflammation and tissue damage, while anti-inflammatory cytokines help resolve inflammation and facilitate tissue repair. Over the past few decades, this general feature of cytokine-mediated events has offered a broad framework to comprehend the pathogenesis of autoimmune and other immune-mediated diseases, and to successfully develop therapeutic approaches for diseases such as rheumatoid arthritis (RA). Anti-tumor necrosis factor-α (TNF-α) therapy is a testimony in support of this endeavor. However, many patients with RA fail to respond to this or other biologics, and some patients may suffer unexpected aggravation of arthritic inflammation or other autoimmune effects. These observations combined with rapid advancements in immunology in regard to newer cytokines and T cell subsets have enforced a re-evaluation of the perceived pathogenic attribute of the pro-inflammatory cytokines. Studies conducted by others and us in experimental models of arthritis involving direct administration of IFN-γ or TNF-α; in vivo neutralization of the cytokine; the use of animals deficient in the cytokine or its receptor; and the impact of the cytokine or anti-cytokine therapy on defined T cell subsets have revealed paradoxical anti-inflammatory and immunoregulatory attributes of these two cytokines. Similar studies in other models of autoimmunity as well as limited studies in arthritis patients have also unveiled the disease-protective effects of these pro-inflammatory cytokines. A major mechanism in this regard is the altered balance between the pathogenic T helper 17 (Th17) and protective T regulatory (Treg) cells in favor of the latter. However, it is essential to consider that this aspect of the pro-inflammatory cytokines is context-dependent such that the dose and timing of intervention, the experimental model of the disease under study, and the differences in individual responsiveness can influence the final outcomes. Nevertheless, the realization that pro-inflammatory cytokines can also be immunoregulatory offers a new perspective in fully understanding the pathogenesis of autoimmune diseases and in designing better therapies for controlling them.