The immune dysfunction in ankylosing spondylitis patients

Osteoimmunology: Crosstalk Between T Cells and Osteoclasts in Osteoporosis

Osteoporosis, a common metabolic condition that affects the bones, increases the risk of fractures, thereby diminishing one's quality of life and, in severe cases, can even result in life-threatening conditions. Osteoporosis is becoming increasingly prevalent worldwide as the population ages. Previous research on osteoporosis has focused on skeletal cellular components such as osteoblasts and osteoclasts. The emerging field of "osteoimmunology" has recently been introduced through new research. The concept highlights the critical impact of bone-immune system interactions on osteoporosis progression. The pathogenesis of osteoporosis is significantly influenced by T cells, particularly cytotoxic and helper T cells, which modulate osteoclast differentiation and activity. A crucial aspect of understanding osteoporosis is how T lymphocytes interact with osteoclasts. However, the precise mechanisms underlying T cell-osteoclast crosstalk remain poorly understood. This review systematically examines T cell and osteoclast involvement in osteoimmunology, with a particular focus on their involvement in osteoporosis. It seeks to elucidate the immune mechanisms driving the progression of osteoporosis and identify key molecules involved in T cell-osteoclast interactions. This aims to discover novel molecular targets and intervention strategies to improve early diagnosis and management of osteoporosis. Furthermore, this article will explore the potential of intervening in T cell-osteoclast interactions using conventional therapies, traditional Chinese medicine, immunomodulatory agents, and nanomaterial-based treatments, providing new perspectives for future osteoporosis management.

Genetic Susceptibility and Disease Activity in Ankylosing Spondylitis: The Role of G Protein-Coupled Receptor 35rs4676410 Polymorphism in a Turkish Population

Background: Ankylosing spondylitis (AS) is a chronic inflammatory disorder with a significant genetic predisposition. Genome-wide association studies (GWAS) have identified immune-related loci, including the G Protein-Coupled Receptor 35 (GPR35) gene, as potential contributors to AS pathogenesis. This study aimed to evaluate the association between the rs4676410 polymorphism in the GPR35 gene and both AS susceptibility and disease activity in a Turkish population. Methods: This case-control study included 200 participants (100 AS patients and 100 healthy controls). DNA was isolated from blood samples, and the rs4676410 polymorphism was analyzed using real-time polymerase chain reaction (PCR). Disease activity in AS patients was assessed using the Bath AS Functional Index (BASFI), Bath AS Disease Activity Index (BASDAI), and disease activity scores including C-reactive protein (ASDAS-CRP) scores. Statistical analyses were conducted using IBM SPSS 26. Results: The rs4676410 polymorphism was significantly associated with AS susceptibility. The AA genotype and A allele were more prevalent in AS patients, indicating an increased risk of developing AS. Among disease activity measures, ASDAS-CRP scores were significantly higher in patients with the AA genotype (p = 0.043), while no significant differences were observed for BASFI and BASDAI scores across genotypes. Conclusion: The findings suggest that the rs4676410 polymorphism in the GPR35 gene is associated with AS susceptibility and may influence disease activity through elevated inflammatory responses. These results highlight the potential of the AA genotype and A allele as genetic markers for AS and underscore the importance of integrating genetic insights into personalized treatment approaches.

Mass cytometry identifies imbalance of multiple immune-cell subsets associated with biologics treatment in ankylosing spondylitis

OBJECTIVE

This study aims to comprehensively investigate immune-cell landscapes in ankylosing spondylitis (AS) patients and explore longitudinal immunophenotyping changes induced by biological agents.

METHODS

We employed mass cytometry with 35 cellular markers to analyze blood samples from 34 AS patients and 13 healthy controls (HC). Eleven AS patients were re-evaluated 1 month (4 patients) and 3 months (7 patients) after treatment with biological agents. Flow Self-Organizing Maps (FlowSOM) clustering was performed to identify specific cellular metaclusters. We compared cellular abundances across distinct subgroups and validated subset differences using gating strategies in flow cytometry scatter plots, visualized with FlowJo software. The proportions of differential subsets were then used for intercellular and clinical correlation analysis, as well as for constructing diagnostic models based on the random forest algorithm.

RESULTS

In AS patients, we identified and validated nine different immune-cell subsets compared to HC. Three subsets increased: helper T-cell 17 (Th17), mucosa-associated invariant T-cell (MAIT), and classical monocytes (CM). Six subsets decreased: effector memory T-cell (TEM), naïve B cells, transitional B cells, IL10+ memory B cells, non-classical monocytes (NCM), and neutrophils. Treatments with biological agents could rectify cellular abnormalities, particularly the imbalance of CM/NCM. Furthermore, these subsets may serve as biomarkers for assessing disease activity and constructing effective diagnostic models for AS.

CONCLUSION

These findings provide novel insights into the specific patterns of immune cell in AS, facilitating the further development of novel biomarkers and potential therapeutic targets for AS patients.

Causal relationship between the immune cells and ankylosing spondylitis: univariable, bidirectional, and multivariable Mendelian randomization

Background

Ankylosing spondylitis (AS) is an autoimmune disease that affects millions of individuals. Immune cells have been recognized as having a crucial role in the pathogenesis of AS. However, their relationship has not been fully explored.

Methods

We chose to employ Mendelian randomization (MR) to investigate the potential correlation between immune cells and AS. We sourced the data on immune cells from the latest genome-wide association studies (GWASs). We obtained data on AS from the FinnGen consortium. Our comprehensive univariable MR analysis covered 731 immune cells to explore its potential causal relationship with AS. The primary analysis method was inverse-variance weighted (IVW). Additionally, we used Cochran's Q test and the MR-Egger intercept test to assess the presence of pleiotropy and heterogeneity. We examined whether our results could be influenced by individual single-nucleotide polymorphisms (SNPs) using the leave-one-out test. We conducted a bidirectional MR to investigate the reverse relationship. We also applied multivariable MR to decrease the potential influence between the immune cells.

Results

Overall, our univariable MR analysis revealed eight immune cells associated with AS. Among these, four immune cells contributed to an increased risk of AS, while four immune cells were identified as protective factors for AS. However, the Bonferroni test confirmed only one risk factor and one protective factor with a significance level of p < 6.84E-05. CD8 on effector memory CD8+ T cell could increase the risk of AS (p: 1.2302E-05, OR: 2.9871, 95%CI: 1.8289-4.8786). HLA DR on CD33dim HLA DR+ CD11b+ could decrease the risk of AS (p: 1.2301E-06, OR: 0.5446, 95%CI: 0.4260-0.6962). We also identified a bidirectional relationship between CD4 on CD39+ activated CD4 regulatory T cells and AS utilizing the bidirectional MR. To address potential confounding among immune cells, we employed multivariable MR analysis, which revealed that only one immune cell had an independent effect on AS. HLA DR on CD33dim HLA DR+ CD11b+ could decrease the risk of AS (p: 2.113E-06, OR: 0.0.5423, 95%CI: 0.4210-0.6983). Our findings were consistently stable and reliable.

Conclusions

Our findings indicated a potential link between immune cells and AS, which could provide a new idea for future research. Nevertheless, the specific underlying mechanisms require further exploration.

Chronic non-bacterial osteomyelitis and immune checkpoint molecules

OBJECTIVE

We aimed to investigate the plasma levels and cell surface expression of two checkpoint molecules, TIM-3 (T cell immunoglobulin and mucin domain-containing protein 3) and PD-1 (programmed cell death protein 1), in pediatric patients with chronic non-bacterial osteomyelitis (CNO).

METHODS

Plasma samples of CNO patients were collected at diagnosis or during biologic agent treatment. Plasma levels of TIM-3 and PD-1 were measured using the sandwich enzyme-linked immunosorbent assay method, and the expression of the two immune checkpoint molecules on the cell surface was analyzed by isolating peripheral blood mononuclear cells by density gradient centrifugation technique.

RESULTS

Twenty-seven patients with CNO (14 boys, 51.9%) and six healthy controls (3 boys, 50%) were enrolled in the study. There were no age differences between CNO patients and healthy controls (median age 14.5 vs. 13.5 years, respectively, p=0.762). Of the CNO patients, 18 were included at the time of diagnosis while 9 were receiving biologic treatment at enrollment. The median plasma PD-1 levels were significantly lower in the CNO group than in the healthy controls (p=0.011). However, no significant difference was found in the cellular expression of PD-1 and TIM-3 on CD3+CD4+ T cells in patients and healthy controls (p=0.083 and p=0.245, respectively). There was also no statistically significant difference in plasma TIM-3 levels of the patient and control groups (p=0.981).

CONCLUSION

CNO is an autoinflammatory disease, and overall, our results suggest that T cell exhaustion may not be significant in CNO. Further research is needed to find out whether the immune checkpoints are mainly associated with autoimmunity but not autoinflammation. Key Points • The median plasma PD-1 levels were significantly lower in the CNO group than in the healthy controls. • No significant difference was found in the cellular expression of PD-1 and TIM-3 on CD3+CD4+ T cells in patients and healthy controls. • Our results suggest that T cell exhaustion may not be significant in CNO pathogenesis.

What do we know about co-stimulatory and co-inhibitory immune checkpoint signals in ankylosing spondylitis?

Ankylosing spondylitis is the main entity of a family of inflammatory diseases affecting many musculoskeletal (sacroiliac joints, spine, and peripheral joints) and extra-musculoskeletal sites, termed spondyloarthritis. While it is debated whether disease onset is primarily driven by autoimmune or autoinflammatory processes, what is certain is that both innate and adaptive immune responses orchestrate local and systemic inflammation, which leads to chronic pain and immobility. Immune checkpoint signals are one key player in keeping the immune system in check and in balance, but their role in disease pathogenesis is still rather elusive. Therefore, we ran a MEDLINE search utilizing the PubMed platform for a variety of immune checkpoint signals in regard to ankylosing spondylitis. In this review, we summarize the experimental and genetic data available and evaluate the relevance of immune checkpoint signalling in the pathogenesis of ankylosing spondylitis. Markers such as PD-1 and CTLA-4 have been extensively studied and facilitate the concept of an impaired negative immune regulation in ankylosing spondylitis. Other markers are either neglected completely or insufficiently examined, and the data is conflicting. Still, some of those markers remain interesting targets to decipher the pathogenesis of ankylosing spondylitis and to develop new treatment strategies.

Curcumin and Curcuma longa Extract in the Treatment of 10 Types of Autoimmune Diseases: A Systematic Review and Meta-Analysis of 31 Randomized Controlled Trials

Objective

To evaluate the randomized controlled trials (RCTs) of Curcumin and Curcuma longa Extract in the treatment of autoimmune diseases.

Methods

Databases such as Embase, Web of Science, PubMed and The Cochrane Library were searched from the database establishment to February 2022 to collect RCTs of Curcumin and Curcuma longa Extract in the treatment of autoimmune diseases. Then the literature was screened and the data were extracted. Meta-analysis was performed using RevMan 5.3 software.

Results

A total of 34 records were included, involving 31 RCTs and 10 types of autoimmune disease. Among them, ankylosing spondylitis (AS) involves one RCT, Behcet ‘s disease (BD) involves one RCT, Crohn ‘s disease involves two RCTs, multiple sclerosis (MS) involves two RCTs, oral lichen planus involves six RCTs, psoriasis involves two RCTs, rheumatoid arthritis (RA) involves five RCTs, systemic lupus erythematosus (SLE) involves two RCTs, arteritis involves one RCT, ulcerative colitis (UC) involves nine RCTs. Among them, most of the RCTs of ulcerative colitis (UC), oral lichen planus, RA showed that curcumin and curcumin extracts improved clinical or laboratory results. Crohn ‘ s disease, MS, SLE, psoriasis included two RCTs; they all showed improvements (at least one RCT reported improvements in clinical outcomes). AS, BD and arteritis included only one RCT, and the clinical results showed improvement. However, due to the small number of RCTs and the small number of patients involved in each disease, there is still a need for more high-quality RCTs.

Conclusion

Curcumin and Curcuma longa Extract had good clinical efficacy in the treatment of Psoriasis, UC and RA, so Curcumin and Curcuma longa Extract could be used in the treatment of the above diseases in the future. The results of Meta-analysis showed that Curcumin and Curcuma longa Extract did not show efficacy in the treatment of oral lichen planus, while Takayasu arteritis, SLE, MS, AS, BD and CD did not report sufficient clinical data for meta-analysis. Therefore, large-sample, multi-center clinical trials are still needed for revision or validation.

Revisiting PD-1/PD-L pathway in T and B cell response: Beyond immunosuppression

The regulation of T cell response depends on co-inhibitory pathways that serve to control immune-mediated tissue damage and resolve inflammation by modulating the magnitude and duration of immune response. In this process, the axis of T-cell-expressed programmed death-1 (PD-1) and its ligands (PD-L1 and PD-L2) play a key role. While the PD-1/PD-L pathway has received considerable attention for its role in the maintenance of T cell exhaustion in cancer and chronic infection, the PD-1/PD-L pathway also plays diverse roles in regulating host immunity beyond T cell exhaustion. In this review, we will discuss emerging concepts in co-stimulatory functions of PD-1/PD-L pathway on T cell- and B cell response and explore the potential underlying mechanisms. In addition, based on the elevated expression of PD-1 and its ligands in local inflamed tissues, we further discussed the role of PD-1/PD-L pathway in autoimmune diseases.

Interleukin-35 promotes Breg expansion and interleukin-10 production in CD19+ B cells in patients with ankylosing spondylitis

OBJECTIVE

IL-35 is a potent immunosuppressive and anti-inflammatory cytokine, consisting of a p35 subunit and an Epstein-Barr virus-induced gene 3 (EBI3) subunit, which suppresses CD4⁺ effector T cell proliferation and promotes regulatory T cell (Treg) expansion. However, the effects of IL-35 on regulatory B cells (Bregs) in ankylosing spondylitis (AS) have not been explored. The present study aimed (i) to measure serum IL-35 levels and the percentages of Bregs in the peripheral blood of patients with AS and (ii) to explore their relationships in the pathogenesis of AS.

METHODS

A total of 77 patients with AS (AS group), including 47 inactive AS and 30 active AS cases, and 59 healthy controls (HCs) were enrolled into this study. The serum levels of IL-35 and IL-10 were detected by ELISA, and the mRNA levels of p35 and EBI3 were measured by RT-qPCR. The percentages of CD19⁺CD24^hiCD38^hi and CD19⁺CD24^hiCD27⁺ Bregs and IL-35 receptor (IL-12Rβ2, IL-27Rα and gp130), IL-10, p-STAT1, p-STAT3, and p-STAT4 in CD19⁺ B cells were detected by flow cytometry. The correlations between IL-35 levels and percentages of Bregs were analyzed by determining Pearson's correlation coefficient. The effect of IL-35 on Bregs was determined by mix-culture of recombinant (r) IL-35 with peripheral blood mononuclear cells (PBMCs).

RESULTS

The serum IL-35 and IL-10 levels, p35 and EBI3 mRNA levels, and the percentages of CD19⁺CD24^hiCD38^hi and CD19⁺CD24^hiCD27⁺ Bregs were significantly lower in AS patients than those in HCs. In addition, the percentages of CD19⁺CD24^hiCD38^hi and CD19⁺CD24^hiCD27⁺ Bregs in active AS patients were significantly lower than those in inactive AS patients. The serum IL-35 levels were positively correlated with the percentages of CD19⁺CD24^hiCD38^hi and CD19⁺CD24^hiCD27⁺ Bregs in AS patients. IL-12Rβ2 and IL-27Rα, but not gp130 subunit, were expressed in CD19⁺ B cells in AS patients. RIL-35 could effectively promote CD19⁺CD24^hiCD38^hi Breg expansion and IL-10 production. Meanwhile, rIL-35 also promoted the expression of IL-12Rβ2 and IL-27Rα and the phosphorylation of STAT1 and STAT3 in CD19⁺ B cells.

CONCLUSION

These results demonstrated that reduced IL-35 production may be associated with Bregs defects in AS patients. RIL-35 induced the proliferation of CD19⁺CD24^hiCD38^hi Bregs and IL-10 production, suggesting that IL-35 may serve as a reference for further investigation to develop novel treatments for AS. Key Points • Our study investigated the effects of IL-35 on Bregs in AS patients. • We found the serum IL-35, IL-10 levels, and the percentages of CD19⁺CD24^hiCD38^hi and CD19⁺CD24^hiCD27⁺ Bregs were significantly lower in AS patients. • The serum IL-35 levels were positively correlated with the percentages of CD19⁺CD24^hiCD38^hi and CD19⁺CD24^hiCD27⁺ Bregs in AS patients. • Recombinant IL-35 could effectively promote CD19⁺CD24^hiCD38^hi Breg expansion and IL-10 production.

The Potential Role of Genetics, Environmental Factors, and Gut Dysbiosis in the Aberrant Non-Coding RNA Expression to Mediate Inflammation and Osteoclastogenic/Osteogenic Differentiation in Ankylosing Spondylitis

Ankylosing spondylitis (AS) or radiographic axial spondyloarthritis is a chronic immune-mediated rheumatic disorder characterized by the inflammation in the axial skeleton, peripheral joints, and soft tissues (enthesis, fascia, and ligament). In addition, the extra-skeletal complications including anterior uveitis, interstitial lung diseases and aortitis are found. The pathogenesis of AS implicates an intricate interaction among HLA (HLA-B27) and non-HLA loci [endoplasmic reticulum aminopeptidase 1 (ERAP1), and interleukin-23 receptor (IL23R), gut dysbiosis, immune plasticity, and numerous environmental factors (infections, heavy metals, stress, cigarette smoking, etc.) The latter multiple non-genetic factors may exert a powerful stress on epigenetic regulations. These epigenetic regulations of gene expression contain DNA methylation/demethylation, histone modifications and aberrant non-coding RNAs (ncRNAs) expression, leading to inflammation and immune dysfunctions. In the present review, we shall discuss these contributory factors that are involved in AS pathogenesis, especially the aberrant ncRNA expression and its effects on the proinflammatory cytokine productions (TNF-α, IL-17 and IL-23), T cell skewing to Th1/Th17, and osteoclastogenic/osteogenic differentiation. Finally, some potential investigatory approaches are raised for solving the puzzles in AS pathogenesis.

Elevated Th17 cells are associated with cardiovascular complications in ankylosing spondylitis

OBJECTIVE

Patients with ankylosing spondylitis (AS) carry an increased burden of cardiovascular diseases (CVD), but features denoting the development of CVD in AS are unclear. This study aimed to evaluate the percentage and absolute number of lymphocytes and CD4+T cells in AS patients complicated with CVD (AS-CVD) and determine whether circulating Th17 cells are associated with the development of CVD in AS.

METHOD

A total of 117 AS patients (46 had CVD and 71 had no CVD) were enrolled in this retrospective study. The percentage and absolute number of lymphocytes and CD4+T cells were determined by Flow cytometry. Associations between CVD and clinical markers were analyzed using logistic regression.

RESULTS

The ratio of Th17/Treg cells (0.30 vs 0.19, p = 0.014) and the absolute number of Th17 cells (7.27 cells/μL vs 4.34 cells/μL, p < 0.001) was significantly elevated in AS-CVD group compared with AS-no-CVD group. Multivariate logistic regression revealed that elevated Th17 cells (OR = 1.20, p = 0.016) were associated with CVD complications in AS. Receiver operating characteristic (ROC) curves showed a contribution of Th17 cell for distinguishing AS patients with CVD, with the areas under the ROC curve (AUCs) of 0.729 (95%CI: 0.632-0.825, p < 0.001).

CONCLUSION

Our findings provide evidence for the association between Th17 cells and increased cardiovascular risk in AS. Th17 cells may contribute to accelerated atherogenesis and increased cardiovascular burden in AS and be valuable for early assessment and management of AS-CVD.

Identification of immune related cells and crucial genes in the peripheral blood of ankylosing spondylitis by integrated bioinformatics analysis

Background

Ankylosing spondylitis (AS) is a progressive rheumatic disease and studies reveal that the immune system is critical for the pathogenesis of AS. In the present study, various bioinformatics analysis methods were comprehensively applied, designed to identify potential key genes and inflammation states of AS.

Methods

The transcriptome profiles of GSE25101 and GSE73754 obtained from the Gene Expression Omnibus (GEO) database were merged for subsequent analyses. The differentially expressed genes (DEGs) were identified using the Bioconductor package Limma and threshold values. Functional enrichment and pathway enrichment analyses were performed using the clusterProfiler package and Gene Set Enrichment Analysis (GSEA). Next, protein-protein interaction (PPI) network of the identified DEGs was constructed by the online database, the Search Tool for the Retrieval of Interacting Genes (STRING), visualization and analysis were performed through Cytoscape software. Subsequently, we applied CIBERSORT algorithm to identify subpopulation proportions of immune cells in peripheral blood samples. Finally, we validated the hub genes with the GSE18781 dataset. Samples were collected from patients to validate gene and protein expression using qRT-PCR and ELISA.

Results

A total of 334 DEGs were identified, including 182 upregulated and 152 downregulated DEGs, between AS patients and normal human controls, which were primarily involved in immune response, autophagy, and natural killer cell-mediated cytotoxicity. The most prominent module and candidate biomarkers were identified from the PPI network. Biomarkers were selected for validation and their expressions were significantly decreased in peripheral blood samples which was consistent with transcriptome sequencing results. Nine genes with AUC > 0.70 were considered to be AS hub genes for ROC curve analysis, including GZMA, GZMK, PRF1, GNLY, NKG7, KLRB1, KLRD1, IL2RB and CD247. Furthermore, CIBERSORT results suggest that AS contained a higher proportion of CD8+ T cells, naive CD4+ T cells, neutrophils, and lower levels of gamma delta T cells compared with the normal controls.

Conclusion

In this study, we identified DEGs combined with their closely related biological functions and propose that granule-associated proteins and immune infiltration maybe involved in the progression of ankylosing spondylitis. These validated hub genes may provide new perspectives for understanding the molecular mechanisms of ankylosing spondylitis.

Imbalance of Peripheral Lymphocyte Subsets in Patients With Ankylosing Spondylitis: A Meta-Analysis

Ankylosing spondylitis is a complicated consequence of genetic predisposition and environmental factors. Enthesitis is believed to be the hallmark of ankylosing spondylitis, and the chronic inflammatory state of this disease is perpetuated by the disturbances of both the innate immune system and the acquired immune system. To clarify the alteration of immune system in patients with AS, we conducted a meta-analysis concerning the proportions of major lymphocyte subsets in the peripheral blood of AS patients. We systematically searched PubMed and China National Knowledge Infrastructure (CNKI) for articles related to this subject. A total of 95 articles involving 4,020 AS patients and 3,065 healthy controls were included in the analysis. This meta-analysis is performed on R platform using R package "meta", and Egger's tests were used to determine the presence of publication bias. Results showed that the percentages of T cells, NK cells and NKT cells were not significantly different between AS patients and healthy controls, but B cells were significantly increased. Among the subsets of T cells, the proportions of CD4+ T cells, Th17 cells, Tfh cells as well as Th1/Th2 ratio were significantly increased, while Tregs were significantly decreased. Subgroup analysis showed that the proportions of Th17 among both PBMCs, T cells and CD4+ T cells were significantly elevated, while Tregs were only significantly lower in PBMCs. Subgroup analysis also demonstrated that Tregs defined by "CD4+CD25+FoxP3+", "CD4+CD25+CD127low"or "CD4+CD25+CD127-"were significantly downregulated, indicating that the selection of markers could be critical. Further study is warranted in order to elucidate the complicated interactions between different lymphocyte subsets in AS patients. This study implied that the disequilibrium between Th17 and Tregs, as well as between Th1 and Th2 could contribute to the pathogenesis of ankylosing spondylitis, further cementing the understanding that ankylosing spondylitis is a consequence of disrupted balance of innate immune system and acquired immune system.

Ankylosing spondylitis risk factors: a systematic literature review

Radiographic axial spondyloarthritis (also known as ankylosing spondylitis [AS]) is a chronic immune-mediated arthritis characterized by inflammation of the axial skeleton, peripheral joints, and entheses. It is estimated that 1 in every 200 people are affected by AS, making it an important healthcare and socioeconomic issue. In this review, we aim to explore the current understanding of AS risk factors and provide a comprehensive update. Multiple search strings were used to identify articles of interest published in PubMed between January 1, 2013, and February 1, 2021. On the basis of the literature review and analysis, we present up-to-date information on the risk factors of developing AS and our viewpoints on disease onset and progression. Multiple genetic and nongenetic risk factors have been suggested in the onset of AS. HLA-B27 is known to have a strong association with the disease, but other genes have been implicated in disease development. Aside from genetics, other factors are thought to be involved; up to 70% of patients with AS have subclinical intestinal inflammation, suggesting that the origin of the disease may be in the gut. The exact mechanism by which AS onset begins is most likely complex and multifactorial. Key Points • It remains unclear how interactions between genes, microbes, mechanical stress, gender, and other environmental and lifestyle factors predispose patients to the development of ankylosing spondylitis (AS). • The exact mechanisms of AS are complex and multifactorial which will require much future research • Recognizing the risk factors, as well as understanding gene-environment interactions, may offer valuable insights into the etiology of AS and have important implications for diagnosis and treatment strategies.

Osteoimmunological insights into the pathogenesis of ankylosing spondylitis

Ankylosing spondylitis (AS) is inflammatory arthritis predominantly affecting the spine, which is involved in the disorders of both immune and skeletal systems. The exact pathogenesis of AS is not fully understood. Osteoimmunology is a new subject of study in inflammatory arthritis, in particular the pathogenic events involved in the cross-regulation of both skeletal and immune systems. In this review, we discuss osteoimmunological and pathological changes of AS in the spine that are characterized by altered osteogenesis and osteolytic bone destruction, accompanied by the changes of the immune system. It was revealed that bone cells like mesenchymal stem cells, osteoblast, and osteoclast in crossing talking with immune cells such as T cells, B cells coregulate to the pathogenesis of AS. Further, an array of cytokines and molecules expressed by both skeletal and immune systems contribute to these complex interplays. Understanding the cellular and molecular mechanisms underlying the pathogenesis of AS will lay a foundation for the exploration of the potential new treatment to AS.

Modulatory Impact of Adipose-Derived Mesenchymal Stem Cells of Ankylosing Spondylitis Patients on T Helper Cell Differentiation

The domination of pro-inflammatory Th subsets (Th1, Th17) is characteristic of ankylosing spondylitis (AS). Mesenchymal stem cells (MSC) were reported to normalize Th imbalance, but whether MSCs from AS adipose tissue (AS/ASCs) possess such properties is unknown. We examined AS/ASCs' impact on Th-cell differentiation, using healthy donors ASCs (HD/ASCs) as a control. The assessment of the expression of transcription factors defining Th1 (T-bet), Th2 (GATA3), Th17 (RORc), and Treg (FoxP3) subsets by quantitative RT-PCR, the concentrations of subset-specific cytokines by ELISA, and Treg (CD4⁺CD25^highFoxP3⁺) formation by flow cytometry, were performed in the co-cultures of ASCs with activated CD4⁺ T cells or peripheral blood mononuclear cells (PBMCs). AS/ASCs and HD/ASCs exerted similar immunomodulatory effects. Acting directly on CD4⁺ T cells, ASCs decreased the T-bet/GATA3 and RORc/FoxP3 ratios, diminished Treg formation, but increase IFNγ and IL-17AF production, while ASCs co-cultured with PBMCs enhanced Treg generation and reduced IFNγ release. ASCs failed to up-regulate the anti-inflammatory IL-10 and TGFβ. AS/ASCs' impact on allogeneic and autologous PBMCs was similar. In conclusion, to shift Th differentiation to a functional anti-inflammatory direction, ASCs require accessory cell support, whereas their direct effect may be pro-inflammatory. Because ASCs neither inhibit IL-17AF nor up-regulate anti-inflammatory cytokines, their usefulness for AS patients' treatment remains uncertain.

TNF-α inhibitor therapy can improve the immune imbalance of CD4+ T cells and negative regulatory cells but not CD8+ T cells in ankylosing spondylitis

BACKGROUND

Studies into ankylosing spondylitis (AS) and its relationship with immune imbalance are controversial, and the correlation between the efficacy of TNF-α inhibitor and changes in immune imbalance is unclear.

METHODS

A total of 40 immune cells were tested with flow cytometry, and the results of 105 healthy control (HC) subjects, 177 active-stage AS patients, and 23 AS cases before and after 12 weeks of TNF-α inhibitor therapy (Anbainuo) were analyzed.

RESULTS

Compared with the HC group, the proportion of immune cells, such as naïve and central memory CD4+T cells, in AS increased (P < 0.0001), but effector memory and terminally differentiated CD4+T cells were decreased (P < 0.01 and 0.0001, respectively). Naïve, central memory, and effector memory CD8+T cells were increased (P < 0.0001, 0.001, and 0.01, respectively), but terminally differentiated CD8+T cells were decreased (P < 0.0001). Th1 cells (helper T cells-1), Tfh1 cells (follicular helper T cells-1), Tc1 cells (cytotoxic T cells-1), and Tregs (regulatory T cells) were lower (P < 0.01, 0.05, 0.0001, and 0.001, respectively), but Th17 cells, Tfh17 cells, and Tc cells were higher (P < 0.001, 0.0001, and 0.001, respectively). The proportions of total B cells and class-switched B cells were increased (P < 0.05), but non-switched B cells, plasma cells, memory B cells, and immature Bregs (regulatory B cells) were lower (P < 0.01, 0.0001, 0.0001, and 0.0001, respectively). After Anbainuo therapy, the percentage of naïve CD4+ T cells had decreased (P < 0.05) but Tregs and B10 cells (IL-10-producing regulatory B cells) had increased (P < 0.01 and 0.05, respectively), and the increase in Tregs was positively correlated with the decrease in C-reactive protein (CRP) (r = 0.489, P = 0.018).

CONCLUSIONS

We found that active-stage AS patients have an immunity imbalance of frequency involving multiple types of immune cells, including CD4+T cells, CD8+T cells, Th cells, Tfh cells, Tc cells, Tregs, Bregs, and B cells. TNF-α inhibitor Anbainuo can not only help to inhibit disease activity but can also improve the immune imbalance of CD4+ T cells and negative regulatory cells in frequency. But CD8+ T cells have not been rescued.

The PD-1/PD-L pathway in rheumatic diseases

BACKGROUND/PURPOSE

Autoimmune diseases are diseases in which the body produces an abnormal immune response to self-antigens and damages its own tissues. Programmed death-1 (PD-1) and its ligands (PD-Ls) have been discovered to be important negative regulators of the immune system, playing crucial roles in autoimmunity.

METHODS

We analyzed the existing scientific literature dealing with this issue. In this review, the PD-1/PD-L pathway in the genetic susceptibility to and pathogenesis of rheumatic diseases is discussed. The PD-1/PD-L pathway might be helpful for diagnosing, evaluating the disease activity of and treating rheumatic diseases.

RESULTS

PD-1/PD-L gene polymorphisms are associated with a genetic predisposition to rheumatic disorders, which can provide reference information for diagnosis and disease activity. The conclusion of the crucial role of the PD-1/PD-L pathway in the pathogenesis of rheumatic diseases is consistent, but the details remain controversial. In some animal models, manipulating the PD-1/PD-L pathway could decrease disease severity. PD-1/PD-Ls may enable us to develop new therapeutics for patients with rheumatic diseases in the future.

CONCLUSION

The PD-1/PD-L pathway plays crucial roles in rheumatic disease. More work is needed to provide a better mechanistic understanding of the PD-1/PD-L pathway and to facilitate the precise therapeutic manipulation of this pathway.

Meta-Analysis of Changes in the Number and Proportion of Regulatory T Cells in Patients with Ankylosing Spondylitis

Studies on the number and proportion of regulatory T cells (Tregs) in ankylosing spondylitis (AS) patients have been controversial, which has led to a disagreement regarding the role of Tregs in the pathogenesis of AS. To clarify this debate, we conducted a meta-analysis to verify the reported changes in Tregs during AS. We systematically searched the PubMed, Foreign Medical Retrieval System (FMRS), and China National Knowledge Infrastructure (CNKI) web of knowledge databases for eligible articles. A meta-analysis of studies that examined the proportion and number of Tregs among peripheral blood mononuclear cells (PBMCs) and CD4⁺ T cells was performed using Stata software. Further, subgroup analysis was performed based on Treg definition markers and disease activity to identify potential sources of heterogeneity. Forty-seven studies involving a total of 4373 participants were included in the meta-analysis. The Treg/PBMC and Treg/CD4⁺ T cell ratios were significantly lower in AS patients than those in healthy controls (HCs). A subgroup analysis indicated that patients defined by CD4⁺CD25^+/high, CD4⁺CD25⁺CD127^low/-, and CD4⁺CD25⁺FOXP3⁺ had much lower Treg/PBMC and Treg/CD4⁺ T cell ratios than HCs. Active AS patients also had a substantially lower proportion of Tregs/PBMCs and Treg/CD4⁺ T cells than HCs. The proportion of Tregs among both PBMCs and CD4⁺ T cells was significantly decreased in AS patients. Treg definition markers and disease activity may influence the proportion of Tregs measured among the PBMC and CD4⁺ T cell populations. Further study of the correlation between AS disease activity and the proportion of Tregs in peripheral blood is needed to determine the physiological role of this association. This study implies that loss of Tregs may play a role in the pathogenesis of AS and helps clarify the contradictory Treg results in AS patients. This trial is registered with PROSPERO (CRD42019147064).

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.

Protein inhibitor of activated STAT3 reduces peripheral arthritis and gut inflammation and regulates the Th17/Treg cell imbalance via STAT3 signaling in a mouse model of spondyloarthritis

Background

Spondyloarthritis (SpA) is chronic inflammatory arthritis, and interleukin (IL)-17 is crucial in SpA pathogenesis. Type 17 helper T (Th17) cells are one of major IL-17-secreting cells. Signal transducer and activator of transcription (STAT)-3 signaling induces Th17 differentiation. This study investigated the effects of protein inhibitor of activated STAT3 (PIAS3) on SpA pathogenesis. Curdlan was injected into SKG ZAP-70^W163C mice for SpA induction.

Methods

The PIAS3 or Mock vector was inserted into mice for 10 weeks. Clinical and histologic scores of the paw, spine, and gut were evaluated. The expression of IL-17, tumor necrosis factor-α (TNF-α), STAT3, and bone morphogenic protein (BMP) was measured. Confocal microscopy and flow cytometry were used to assess Th cell differentiation.

Results

PIAS3 significantly diminished the histologic scores of the paw and gut. PIAS3-treated mice displayed decreased expression of IL-17, TNF-α, and STAT3 in the paw, spine, and gut. BMP-2/4 expression was lower in the spines of PIAS3-treated mice. Th cell differentiation was polarized toward the upregulation of regulatory T cells (Tregs) and the downregulation of Th17 in PIAS3-treated mice.

Conclusion

PIAS3 had beneficial effects in mice with SpA by reducing peripheral arthritis and gut inflammation. Pro-inflammatory cytokines and Th17/Treg differentiation were controlled by PIAS3. In addition, BMPs were decreased in the spines of PIAS3-treated mice. These findings suggest that PIAS3 could have therapeutic benefits in patients with SpA.

Identification of key genes in Ankylosing spondylitis

Ankylosing spondylitis (AS) is a common form of seronegative spondyloarthritis. We had identified differentially expressed genes (DEGs) in AS based on our previous RNA-sequencing results. Our study aimed to identify key genes in AS by integrated microarray analysis. In this present study, we identified 1328 DEGs between AS and normal control by using integrated analysis of two datasets derived from the Gene Expression Omnibus (GEO) database. Functional annotation of DEGs were performed. Pathways in cancer, Pancreatic cancer and Natural killer cell mediated cytotoxicity were significantly enriched pathways for DEGs. Based on the shared DEGs of AS in both integrated analysis and our previous RNA-sequencing results, we constructed the protein and protein interaction (PPI) network. BIRC2, MAPILC3A and MAGED1 were hub proteins. Validation of gene expression by qRT-PCR were performed and the results were consistent with our integrated analysis generally. Our finding provided new clues for understanding the mechanism of AS.

The role of interleukin-4 in rheumatic diseases

Rheumatism is a group of diseases, most of which are autoimmune diseases, that violate joints, bones, muscles, blood vessels and related soft tissue. As is well known, cytokines play a role in the pathogenesis of several rheumatic diseases, such as rheumatoid arthritis, spondyloarthritides, and systemic lupus erythematosus. Recently, the role of interleukin-4 (IL-4), which may participate in the mechanism of rheumatism, have been discovered. It is reported that IL-4 takes part in the regulation of T cell activation, differentiation, proliferation, and survival of different T cell types. IL-4 also has an immunomodulatory effect on B cells, mast cells, macrophages, and many cell types. A review of the literature on functions of IL-4 in rheumatic diseases is presented.

The role of innate lymphoid cells in health and disease

Innate lymphoid cells (ILCs) are kind of innate immune cells which can be divided into three main subsets according to their cytokine release profile, transcription factors, and surface markers. ILCs affect the initial stages of immunity in response to microbes and participate in immunity, inflammation, and tissue repair. ILCs modulate immunity through resistance to the pathogens and regulation of autoimmune inflammation and metabolic homeostasis. Therefore dysregulation of ILCs may lead to chronic pathologies such as allergies (i.e., asthma), inflammation (i.e., inflammatory bowel disease), and autoimmunity (i.e., psoriasis, atopic dermatitis, rheumatoid arthritis, multiple sclerosis, and ankylosing spondylitis). Regarding the critical role of ILCs in the regulation of immune system, the elucidation of their function in different conditions makes an interesting target for improvement of novel therapeutic approach to modulate an immune response in different disease context.