Immune checkpoint inhibitor-induced inflammatory arthritis as a model of autoimmune arthritis

Case report: Inflammatory sternoclavicular joint arthritis induced by an immune checkpoint inhibitor with remarkable responsiveness to infliximab

This report describes the case of a 48-year-old woman who presented with sternoclavicular joint arthritis after administration of an immune checkpoint inhibitor (ICI), durvalumab, for small cell lung carcinoma. The onset of arthritis transpired 18 months after the commencement of the ICI therapeutic regimen and demonstrated resilience to glucocorticoid treatment. After excluding infectious aetiologies and metastatic involvement, the patient was diagnosed with ICI-induced arthritis (ICI-IA). Considering the articular implications akin to the SAPHO syndrome, the patient was treated with infliximab, resulting in complete resolution. This finding implies that biological DMARDs can serve as effective interventions for ICI-induced sternoclavicular joint arthritis. Given the heterogeneous nature of its pathogenesis, the selection of therapeutic agents may require customization based on the distinct clinical presentation of each individual case.

The Utility of Laboratory Investigations for the Assessment and Management of Rheumatic Immune Related Adverse Events

Immune checkpoint inhibitors (ICIs) have greatly improved survival of several cancers with historically very poor prognosis. ICIs act by stimulating the patient's own immune system to fight cancer. Simultaneously, this immune activation can lead to immune-related adverse events (irAEs), including rheumatic manifestations (Rh-irAEs). Rh-irAEs mimic primary rheumatic diseases including arthritis, polymyalgia rheumatica, myositis, vasculitis, sarcoidosis, and sicca. This article summarizes the latest evidence regarding the utility of laboratory investigations in Rh-irAEs.

Knowledge domains and emerging trends in immune-related adverse events from immune checkpoint inhibitors: A bibliometrics and visualized analysis

Objective

The primary objective of this paper is to investigate the research hotspots and future trends of immune-related adverse events induced by immune checkpoint inhibitors, offering valuable insights for researchers in this field.

Methodology

Using the visual analysis software, this study conducted quantitative statistics and visualization research on the relevant literature concerning immune-related adverse events caused by immune checkpoint inhibitors in the Web of Science Core Collection Database. By evaluating the publication trends, countries, institutions, keywords, research status, cited documents, and document co-citations, among several others, the discussion revolved around the hot spots and future development trends in this field and provided references for future research.

Findings and conclusions

A total of 514 English articles were included, and the top three countries in the research field at the time of this study were the United States, Japan, and China. More specifically, the University of Texas MD Anderson Cancer Center, Dana-Farber Cancer Institute, and Massachusetts General Hospital have been the top three research institutes with more than 10 publications. The frequency of keyword use linked to immune-related adverse events caused by immune checkpoint inhibitors in literature research has been steadily growing over the years. Additionally, the research with respect to the disease focuses on melanoma, cell lung cancer, hepatocellular carcinoma, and breast cancer. In the context of drugs, cancer-related research has mainly focused on the combined use of nivolumab, pembrolizumab, ipilimumab, and immune checkpoint inhibitors. Meanwhile, research on adverse events has delved into the immune checkpoint inhibitors causing vitiligo, thyroid dysfunction, pancreatitis, cholangitis, and rheumatism. Related studies cover acute arthritis, myositis, acute kidney injury, as well as the combination therapy of immune checkpoint inhibitors and docetaxel, management of irAEs in cancer immunotherapy, and biomarkers of immune adverse reactions of immune checkpoint inhibitors. Finally, case report studies of immune adverse reactions caused by immune checkpoint inhibitors could serve as research hotspots in the future.

STAT4 Gene Variant rs7574865 Is Associated with Rheumatoid Arthritis Activity and Anti-CCP Levels in the Western but Not in the Southern Population of Mexico

Rheumatoid Arthritis (RA) is a multifactorial autoimmune disease. Currently, several genes play an important role in the development of the disease. The objective was to evaluate the association of the STAT4 rs7574865 and rs897200 gene variants with RA susceptibility, DAS28, RF, and anti-CCP in Western and Southern Mexico populations. Genotyping was performed on 476 samples (cases = 240; controls = 236) using the Taqman® system and qPCR probes. Disease activity was assessed using DAS28 and HAQ DI. CRP, ESR, RF, and anti-CCP were determined for clinical assessment. Our study showed there is a statistically significant association with susceptibility to RA for the rs7574865 variant in the Western population for the GT and TT genotypes. The same genotypes also showed a moderate-to-high activity according to DAS28 and positive anti-CCP compared to the control group. This association was not found in the Southern population. This work confirms the association of the rs7574865 variant with RA, as well as a moderate-to-high activity and positive anti-CCP in the Western population but not in the Southern population. No association of the rs897200 variant was found in any of the studied populations.

A Review of Proposed Mechanisms in Rheumatoid Arthritis and Therapeutic Strategies for the Disease

Rheumatoid arthritis (RA) is characterized by synovial edema, inflammation, bone and cartilage loss, and joint degradation. Patients experience swelling, stiffness, pain, limited joint movement, and decreased mobility as the condition worsens. RA treatment regimens often come with various side effects, including an increased risk of developing cancer and organ failure, potentially leading to mortality. However, researchers have proposed mechanistic hypotheses to explain the underlying causes of synovitis and joint damage in RA patients. This review article focuses on the role of synoviocytes and synoviocytes resembling fibroblasts in the RA synovium. Additionally, it explores the involvement of epigenetic regulatory systems, such as microRNA pathways, silent information regulator 1 (SIRT1), Peroxisome proliferatoractivated receptor-gamma coactivator (PGC1-α), and protein phosphatase 1A (PPM1A)/high mobility group box 1 (HMGB1) regulators. These mechanisms are believed to modulate the function of receptors, cytokines, and growth factors associated with RA. The review article includes data from preclinical and clinical trials that provide insights into potential treatment options for RA.

Diagnostic Utility of 99m Tc-MDP Bone Scintigraphy for Nivolumab-Induced Inflammatory Arthritis

ABSTRACT

Immune checkpoint inhibitors can revive exhausted helper T-cells, and inflammatory cell reactivation may cause autoimmune disease-like conditions. Drug-induced arthritis is an immune-related adverse event, but the diagnostic approach is undefined. We present the diagnostic utility of 99m Tc-MDP bone scintigraphy for nivolumab-induced inflammatory arthritis. A 67-year-old man with hypopharyngeal carcinoma presented bilateral multiple metacarpophalangeal joint pain and swelling at each nivolumab administration. Regular imaging findings were atypical for inflammatory arthritis and did not fulfill the criteria for rheumatoid arthritis. We diagnosed nivolumab-induced inflammatory arthritis based on clinical symptoms and the symmetrical moderate uptake of the affected joints on 99m Tc-MDP bone scintigraphy.

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.

Rheumatic complications of checkpoint inhibitors: Lessons from autoimmunity

Immune checkpoint inhibitors are now an established treatment in the management of a range of cancers. Their success means that their use is likely to increase in future in terms of the numbers of patients treated, the indications and the range of immune checkpoints targeted. They function by counteracting immune evasion by the tumor but, as a consequence, can breach self-tolerance at other sites leading to a range of immune-related adverse events. Included among these complications are a range of rheumatologic complications, including inflammatory arthritis and keratoconjunctivitis sicca. These superficially resemble immune-mediated rheumatic diseases (IMRDs) such as rheumatoid arthritis and Sjogren's disease but preliminary studies suggest they are clinically and immunologically distinct entities. However, there appear to be common processes that predispose to the development of both that may inform preventative interventions and predictive tools. Both groups of conditions highlight the centrality of immune checkpoints in controlling tolerance and how it can be restored. Here we will discuss some of these commonalities and differences between rheumatic irAEs and IMRDs.

Clonally expanded CD38hi cytotoxic CD8 T cells define the T cell infiltrate in checkpoint inhibitor-associated arthritis

Immune checkpoint inhibitor (ICI) therapies used to treat cancer, such as anti-PD-1 antibodies, can induce autoimmune conditions in some individuals. The T cell mechanisms mediating such iatrogenic autoimmunity and their overlap with spontaneous autoimmune diseases remain unclear. Here, we compared T cells from the joints of 20 patients with an inflammatory arthritis induced by ICI therapy (ICI-arthritis) with two archetypal autoimmune arthritides, rheumatoid arthritis (RA) and psoriatic arthritis (PsA). Single-cell transcriptomic and antigen receptor repertoire analyses highlighted clonal expansion of an activated effector CD8 T cell population in the joints and blood of patients with ICI-arthritis. These cells were identified as CD38hiCD127- CD8 T cells and were uniquely enriched in ICI-arthritis joints compared with RA and PsA and also displayed an elevated interferon signature. In vitro, type I interferon induced CD8 T cells to acquire the ICI-associated CD38hi phenotype and enhanced cytotoxic function. In a cohort of patients with advanced melanoma, ICI therapy markedly expanded circulating CD38hiCD127- T cells, which were frequently bound by the therapeutic anti-PD-1 drug. In patients with ICI-arthritis, drug-bound CD8 T cells in circulation showed marked clonal overlap with drug-bound CD8 T cells from synovial fluid. These results suggest that ICI therapy directly targets CD8 T cells in patients who develop ICI-arthritis and induces an autoimmune pathology that is distinct from prototypical spontaneous autoimmune arthritides.

Cutaneous immune-related adverse events to immune checkpoint inhibitors: from underlying immunological mechanisms to multi-omics prediction

The development of immune checkpoint inhibitors (ICIs) has dramatically altered the landscape of therapy for multiple malignancies, including urothelial carcinoma, non-small cell lung cancer, melanoma and gastric cancer. As part of their anti-tumor properties, ICIs can enhance susceptibility to inflammatory side effects known as immune-related adverse events (irAEs), in which the skin is one of the most commonly and rapidly affected organs. Although numerous questions still remain unanswered, multi-omics technologies have shed light into immunological mechanisms, as well as the correlation between ICI-induced activation of immune systems and the incidence of cirAE (cutaneous irAEs). Therefore, we reviewed integrated biological layers of omics studies combined with clinical data for the prediction biomarkers of cirAEs based on skin pathogenesis. Here, we provide an overview of a spectrum of dermatological irAEs, discuss the pathogenesis of this "off-tumor toxicity" during ICI treatment, and summarize recently investigated biomarkers that may have predictive value for cirAEs via multi-omics approach. Finally, we demonstrate the prognostic significance of cirAEs for immune checkpoint blockades.

Type 1 diabetes and inborn errors of immunity: Complete strangers or 2 sides of the same coin?

Type 1 diabetes (T1D) is a polygenic disease and does not follow a mendelian pattern. Inborn errors of immunity (IEIs), on the other hand, are caused by damaging germline variants, suggesting that T1D and IEIs have nothing in common. Some IEIs, resulting from mutations in genes regulating regulatory T-cell homeostasis, are associated with elevated incidence of T1D. The genetic spectrum of IEIs is gradually being unraveled; consequently, molecular pathways underlying human monogenic autoimmunity are being identified. There is an appreciable overlap between some of these pathways and the genetic variants that determine T1D susceptibility, suggesting that after all, IEI and T1D are 2 sides of the same coin. The study of monogenic IEIs with a variable incidence of T1D has the potential to provide crucial insights into the mechanisms leading to T1D. These insights contribute to the definition of T1D endotypes and explain disease heterogeneity. In this review, we discuss the interconnected pathogenic pathways of autoimmunity, β-cell function, and primary immunodeficiency. We also examine the role of environmental factors in disease penetrance as well as the circumstantial evidence of IEI drugs in preventing and curing T1D in individuals with IEIs, suggesting the repositioning of these drugs also for T1D therapy.

Seronegative rheumatoid arthritis after combination therapy with ipilimumab and nivolumab for postoperative pancreatic and liver metastases from renal cell carcinoma

Introduction

Since the approval of immune checkpoint inhibitors for renal cell carcinoma treatment, therapeutic efficacy has been enhanced. However, although autoimmune-related side effects may occur, rheumatoid immune-related adverse events seldom develop.

Case presentation

A 78-year-old Japanese man with renal cell carcinoma developed pancreatic and liver metastases after bilateral partial nephrectomy and was treated with ipilimumab and nivolumab. After 22 months, he developed arthralgia in limbs and knee joints, accompanied by limb swelling. The diagnosis was seronegative rheumatoid arthritis. Nivolumab was discontinued, and prednisolone was initiated, quickly improving symptoms. Although nivolumab was resumed after 2 months, arthritis did not recur.

Conclusion

Immune checkpoint inhibitors may cause a wide variety of immune-related adverse events. When arthritis is encountered during immune checkpoint inhibitor administration, seronegative rheumatoid arthritis should be differentiated from other types of arthritis, despite being less frequent.

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.

Successful use of secukinumab in two melanoma patients with immune checkpoint inhibitor-induced inflammatory arthropathy

Immune-related adverse events (irAEs) are a major concern when treating cancer patients with immune checkpoint inhibitor (ICI) therapy. Selecting the most appropriate management of irAEs remains an ongoing challenge because prolonged use of glucocorticoids come with their own side effects and may counteract the antineoplastic effects from immunotherapy. In this case report, we present two patients with metastatic melanoma who developed symptoms of inflammatory arthritis attributed to ICI therapy. We found that treatment with secukinumab, an anti-IL-17A inhibitor, effectively managed their symptoms and did not lead to tumor progression. Our study suggests that secukinumab can be a safe and effective treatment option for ICI-induced inflammatory arthropathy.

Comparison of immune checkpoint inhibitor-induced arthritis and reactive arthritis to inform therapeutic strategy

INTRODUCTION

Immune checkpoint inhibitor-induced inflammatory arthritis (ICI-IA) is a relatively new disease entity caused by ICI agents during cancer therapy. Reactive arthritis (ReA) is a well-known disease entity caused by urogenital or gastrointestinal bacterial infection or pneumonia. In this sense, ICI-IA and ReA are both defined by a reaction to a well-specified causal event. As a result, comparing these diseases may help to determine therapeutic strategies.

METHODS

We compared ICI-IA and ReA with special focus on pharmacological management. Specifically regarding treatment, we conducted a literature search of studies published in the PubMed database. Inclusion criteria were studies on treatment with non-steroidal anti-inflammatory drugs (NSAIDs), glucocorticoids (GC), or disease modifying antirheumatic drugs (DMARDs) in ICI-IA or ReA. During systematic selection, 21 studies evaluating ICI-IA and 14 studies evaluating ReA were included.

RESULTS

In ICI-IA, prospective and retrospective studies have shown effects of non-steroidal anti-inflammatory drugs (NSAIDs), glucocorticoid (GC), sulfasalazine (SSZ), methotrexate (MTX), hydroxychloroquine (HCQ) and TNFi. In ReA, retrospective studies evaluated NSAIDs and GC. A randomized controlled trial reported the effect of SSZ, and a retrospective study reported the effect of MTX and SSZ in combination with tumor necrosis factor alpha inhibition (TNFi). For both entities, small case reports show treatment effects of interleukin 6 receptor inhibition (IL-6Ri).

DISCUSSION

This literature review identified both similarities and differences regarding the pathogenesis and clinical features of ReA and ICI-IA. Studies on treatment reported effectiveness of NSAIDs, GC, MTX, SSZ and TNFi in both diseases. Further, small case reports showed effects of IL-6Ri.

Activated osteoarthritis following immune checkpoint inhibitor treatment: an observational study

Immune checkpoint inhibitors (ICIs) have revolutionized cancer therapy but can result in toxicities, known as immune-related adverse events (irAEs), due to a hyperactivated immune system. ICI-related inflammatory arthritis has been described in literature, but herewith we introduce and characterize post-ICI-activated osteoarthritis (ICI-aOA). We conducted a multicenter, retrospective, observational study of patients with cancer treated with ICIs and diagnosed with ICI-aOA by a rheumatologist. ICI-aOA was defined by (1) an increase in non-inflammatory joint pain after ICI initiation, (2) in joints characteristically affected by osteoarthritis, and (3) lack of inflammation on exam. Cases were graded using the Common Terminology Criteria for Adverse Events (CTCAE) V.6.0 rubric for arthralgia. Response Evaluation Criteria in Solid Tumors V.1.1 (v.4.03) guidelines determined tumor response. Results were analyzed using χ² tests of association and multivariate logistic regression. Thirty-six patients had ICI-aOA with a mean age at time of rheumatology presentation of 66 years (51–81 years). Most patients had metastatic melanoma (10/36, 28%) and had received a PD-1/PD-L1 inhibitor monotherapy (31/36, 86%) with 5/36 (14%) combination therapy. Large joint involvement (hip/knee) was noted in 53% (19/36), small joints of hand 25% (9/36), and spine 14% (5/36). Two-thirds (24/36) suffered multiple joint involvement. Three of 36 (8%) had CTCAE grade 3, 14 (39%) grade 2 and 19 (53%) grade 1 manifestations. Symptom onset ranged from 6 days to 33.8 months with a median of 5.2 months after ICI initiation; five patients suffered from ICI-aOA after ICI cessation (0.6, 3.5, 4.4, 7.3, and 15.4 months after ICI cessation). The most common form of therapy was intra-articular corticosteroid injections only (15/36, 42%) followed by non-steroidal anti-inflammatory drugs only (7/36, 20%). Twenty patients (56%) experienced other irAEs, with rheumatic and dermatological being the most common. All three patients with high-grade ICI-aOA also had another irAE diagnosis at some point after ICI initiation. ICI-aOA should be recognized as an adverse event of ICI immunotherapy. Early referral to a rheumatologist can facilitate the distinction between ICI induced inflammatory arthritis from post-ICI mechanical arthropathy, the latter of which can be managed with local therapy that will not compromise ICI efficacy.

Systemic administration of cytotoxic T lymphocyte-associated antigen 4 (CTLA-4)-Ig abrogates alveolar bone resorption in induced periodontitis through inhibition of osteoclast differentiation and activation: An experimental investigation

BACKGROUND/OBJECTIVES

Cytotoxic T lymphocyte-associated antigen 4 (CTLA-4) is a critical immunoregulatory molecule expressed on T cells. CTLA-4 also binds to the surfaces of monocytes and macrophages, precursors of osteoclasts. Research on rheumatoid arthritis demonstrated that CTLA-4 suppresses inflammation and bone resorption. However, its effects on alveolar bone have yet to be understood. The purpose of this study was to investigate the role and potential mechanism of CTLA-4 in bone resorption in periodontitis.

MATERIALS AND METHODS

In vivo, the effects of systemic administration of CTLA-4 immunoglobulin fusion protein (CTLA-4-Ig) on alveolar bone resorption were investigated using a periodontitis mouse model. A total of 20 C57BL/6J mice were randomly assigned to two groups according to the administration modes. Periodontitis was induced by placing a ligature around the left maxillary second molar. The contralateral tooth was left un-ligated. In the CTLA-4-Ig (+) group, CTLA-4-Ig was administered by intraperitoneal injection at 1 and 3 days after ligature placement. Animals in the CTLA-4-Ig (-) group were given only phosphate-buffered saline each time. At 5 days after ligature placement, bone resorption was assessed by micro-computed tomography and histological examination, and the prevalence of osteoclast-like cells was assessed by tartrate-resistant acid phosphatase (TRAP) staining. In vitro, the effects of CTLA-4-Ig on osteoclasts were evaluated. Viability of RAW 264.7 cells treated with receptor activator of nuclear factor-κB ligand (RANKL) and CTLA-4-Ig was tested by WST-1 assay. Osteoclast-like cells were enumerated by TRAP staining, and osteoclast activity was evaluated by resorption pit assay. Gene expression levels of osteoclast differentiation markers (macrophage-colony stimulating factor receptor, carbonic anhydrase II, cathepsin K, and Trap) and protein phosphatase 2A (PP2A), a major serine-threonine phosphatase, were assessed by quantitative real-time polymerase chain reaction. The effect of CTLA-4-Ig on the nuclear factor-κB (NF-κB) activation was assessed by enzyme-linked immunosorbent assay.

RESULTS

In vivo, ligature-induced bone resorption and the numbers of osteoclast-like cells were significantly decreased by the administration of CTLA-4-Ig. In vitro, treatment with RANKL and CTLA-4-Ig had no significant effect on cell viability. CTLA-4-Ig significantly reduced the prevalence and activation of osteoclast-like cells and decreased the expressions of osteoclast differentiation markers, compared with the RANKL-treated control. CTLA-4-Ig significantly suppressed RANKL-induced phosphorylation of NF-κB p65 but increased PP2A expression.

CONCLUSION

These results suggest that CTLA-4-Ig abrogates bone resorption in induced periodontitis, possibly via inhibition of osteoclast differentiation and activation. The regulation of the NF-κB pathway and PP2A expression may be one mechanism by which CTLA-4-Ig suppresses osteoclast behavior.

Astragaloside regulates lncRNA LOC100912373 and the miR‑17‑5p/PDK1 axis to inhibit the proliferation of fibroblast‑like synoviocytes in rats with rheumatoid arthritis

Previous studies have confirmed that astragaloside (AST) exerts a positive effect on alleviating synovial and joint injury in rheumatoid arthritis (RA). However, the precise mechanisms through which AST acts in the treatment of RA remain unclear. Long non-coding RNA (lncRNA) LOC100912373 was identified as a key gene related to RA and has been proven to interact with miR-17-5p, in order to regulate the pyruvate dehydrogenase kinase 1 and protein kinase B axis (PDK1/AKT axis). The present study aimed to determine whether AST may treat RA through the interaction between lncRNA LOC100912373 and the miR-17-5p/PDK1 axis. MTT assays and flow cytometry were used to detect the proliferation and cell cycle progression of AST-treated fibroblast-like synoviocytes (FLSs). The expression of lncRNA LOC100912373 and miR-17-5p, as well as relative the mRNA expression of the PDK1 and AKT genes following AST intervention was detected by reverse transcription-quantitative PCR (RT-qPCR), immunofluorescence and western blot analysis. The results revealed that AST inhibited FLS proliferation, reduced lncRNA LOC100912373 expression levels, increased miR-17-5p expression levels, and decreased the PDK1 and p-AKT expression levels. Additionally, consecutive rescue experiments revealed that AST counteracted the effects of lncRNA LOC100912373 overexpression on FLS proliferation and cell cycle progression. On the whole, the present study demonstrates that AST inhibits FLS proliferation by regulating the expression of lncRNA LOC100912373 and the miR-17-5p/PDK1 axis.

A20: a master regulator of arthritis

A20, also known as TNF-α-induced protein 3 (TNFAIP3), is an anti-inflammatory protein that plays an important part in both immune responses and cell death. Impaired A20 function is associated with several human inflammatory and autoimmune diseases. Although the role of A20 in mediating inflammation has been frequently discussed, its intrinsic link to arthritis awaits further explanation. Here, we review new findings that further demonstrate the molecular mechanisms through which A20 regulates inflammatory arthritis, and we discuss the regulation of A20 by many factors. We conclude by reviewing the latest A20-associated mouse models that have been applied in related research because they reflect the characteristics of arthritis, the study of which will hopefully cast new light on anti-arthritis treatments.