Th17/IL-17A axis is critical for pulmonary arterial hypertension (PAH) in systemic sclerosis (SSc): SSc patients with high levels of serum IL-17A exhibit reduced lung functions and increased prevalence of PAH.

BACKGROUND: It is thought that systemic sclerosis (SSc) might be a T helper 17 (Th17) cell-driven autoimmune disease. Noticeably, pulmonary arterial hypertension (PAH) is a leading cause of death in patients with SSc. Here, we investigated the association between serum Th17-related cytokines and prevalence of PAH in SSc patients. METHODS: This study included 72 SSc patients and 51 healthy controls (HC). We determined clinical manifestations, immunophenotypes including Th subsets in peripheral blood lymphocytes, and the serum levels of interleukin (IL)-17A, IL-17A/F, IL-17B. IL-17C, IL-17D. IL-1ß, IL-6, IL-21, IL-22, and IL-23. RESULTS: The frequency of Th17 cells was significantly increased in SSc patients compared to HC and was positively correlated with the modified Rodnan skin scores. Furthermore, the serum levels of IL-17A, IL-17D, IL-1ß, and IL-6 were significantly increased in SSc patients compared to HC. SSc patients with detected IL-17A showed high levels of IL-17A/F, IL-1ß, IL-6, and IL-22, and high frequency of Th17 cells. Interestingly, these patients exhibited the reduced lung functions and increased prevalence of PAH significantly compared to patients with undetected IL-17A. Similarly, SSc patients with detected IL-17A and high IL-6 (≥1.2 pg/mL) exhibited the decreased lung functions and increased prevalence of PAH compared to patients with undetected IL-17A and low IL-6. CONCLUSION: We found that SSc patients with high levels of serum IL-17A or both IL-17A and IL-6 show reduced lung functions and high prevalence of PAH. Consequently, it is highly probable that Th17/IL-17A axis is critical for the prevalence of PAH in SSc patients.

Performance of the 2022 ACR/EULAR Classification Criteria in Comparison With the European Medicines Agency Algorithm in Antineutrophil Cytoplasmic Antibody-Associated Vasculitis.

OBJECTIVE: This study aimed to compare the 2022 American College of Rheumatology (ACR)/European Alliance of Associations for Rheumatology (EULAR) classification criteria with the European Medicines Agency (EMA) algorithm for antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV). METHODS: All consecutive, newly diagnosed patients with AAV according to the 2012 Chapel Hill Consensus Conference who visited Keio University Hospital between March 2012 and May 2022 were retrospectively reviewed. Patients were reclassified according to the EMA algorithm and the 2022 ACR/EULAR criteria, and their clinical characteristics were statistically analyzed. RESULTS: A total of 114 patients with AAV were included in the analyses. Using the EMA algorithm as a reference, reclassification of the patients revealed sensitivity and specificity of the 2022 ACR/EULAR criteria of 100% and 96% for eosinophilic granulomatosis with polyangiitis, 40% and 97% for granulomatosis with polyangiitis (GPA), and 90% and 49% for microscopic polyangiitis (MPA), respectively. Approximately half of patients classified as EMA-GPA or EMA-unclassifiable were reclassified as 2022-MPA; these patients were older, were more disposed to be positive for myeloperoxidase (MPO)-ANCA, and had interstitial lung disease (ILD) more frequently than patients with 2022-GPA or non-2022-MPA. Further, some patients positive for MPO-ANCA with biopsy-proven granulomatous inflammation were also reclassified from EMA-GPA to 2022-MPA. Over the mean observation period of 4.0 years, 16 patients died. Overall survival for each classification group differed significantly from the 2022 ACR/EULAR criteria (P = 0.02), but not with the EMA algorithm (P = 0.21). CONCLUSION: Among the patients classified as EMA-GPA or EMA-unclassifiable, older patients with MPO-ANCA and ILD tended to be reclassified as 2022-MPA. The 2022 ACR/EULAR criteria were more useful in prognostic prediction than the EMA algorithm.

Human T follicular helper cells and their impact on IgE and IgG4 production across allergy, malignancy, and IgG4-related disease.

Human T follicular helper (Tfh) cells play a crucial role in orchestrating B cell differentiation, maturation, and immunoglobulin class switching. Recent studies have underscored the presence of Bcl-6 + Tfh cells not only in secondary lymphoid organs but also within tertiary lymphoid structures at inflammatory sites, emphasizing their pivotal role in disease pathogenesis. Furthermore, Tfh cells have been found to transit between lesion sites, lymph nodes, and peripheral blood, as revealed by T cell receptor repertoire analysis. Among Tfh subsets, Tfh2 cells have emerged as central orchestrators in driving the production of IgE and IgG4 from B cells. Their critical role in diseases such as allergy, malignancy, and IgG4-related disease highlights their profound impact on balancing inflammation and immune tolerance. Our current review provides the molecular characteristics of human Tfh cells, the differentiation pathways of Tfh subsets, mechanisms by which Tfh subsets induce IgE and IgG4 production, and their clinical implications in allergy, malignancy, and IgG4-related disease.

Risk factors for adverse drug reactions to sulfamethoxazole-trimethoprim prophylaxis in patients with rheumatic and musculoskeletal diseases.

OBJECTIVES: Risk factors for adverse drug reactions (ADRs) associated with prophylactic sulfamethoxazole-trimethoprim (SMX/TMP) in patients with rheumatic and musculoskeletal diseases undergoing immunosuppressive therapy remain unclear, we aimed to identify the risk factors associated with ADRs. METHODS: Consecutive patients with rheumatic and musculoskeletal diseases, who were admitted to Keio University Hospital and received prophylactic administration of SMX/TMP, were included. Data regarding ADRs to SMX/TMP were collected to identify associated risk factors using multivariable analysis. RESULTS: Of 438 patients included in the analysis, 82 (18.7%) experienced ADRs. Patients in the ADRs group were significantly older, had chronic kidney disease, and exhibited lower lymphocyte and platelet counts, lower albumin levels, lower estimated glomerular filtration rates, higher aspartate aminotransferase levels, and higher ferritin levels than those in the non-ADR group. Regarding underlying rheumatic and musculoskeletal diseases, adult-onset Still's disease (ASD) was associated with a significantly higher incidence of ADRs (67%) than other diseases. Multivariable analysis identified the presence of ASD and low lymphocyte counts as independent risk factors for allergic ADRs, and older age and use of angiotensin-converting enzyme inhibitors/angiotensin receptor blockers for non-allergic ADRs. CONCLUSIONS: Risk factors for ADRs associated with prophylactic SMX/TMP treatment in patients with rheumatic and musculoskeletal diseases were identified.

T follicular helper cells and T peripheral helper cells in rheumatic and musculoskeletal diseases.

Recent technological progress has greatly advanced our understanding of human immunology. In particular, the discovery of human T follicular helper (Tfh) and T peripheral helper (Tph) cells has significantly advanced our understanding of human adaptive immune system. Tfh and Tph cells share similar molecular characteristics and both play critical roles in B cell differentiation and maturation. However, they differ in their functional properties, such as chemokine receptor expression and cytokine production. As a result, Tfh cells are mainly involved in B cell differentiation and maturation in germinal centres of secondary lymphoid tissues, while Tph cells are involved in B cell differentiation and tissue damage in peripheral inflammatory lesions. Importantly, the involvement of Tfh and Tph cells in the pathogenesis of rheumatic and musculoskeletal diseases has become clear. In rheumatoid arthritis and systemic lupus erythematosus, Tph cell infiltration is predominant in peripheral inflammatory lesions, whereas Tfh cell infiltration is predominant in the affected lesions of IgG4-related disease. Therefore, the contribution of Tfh and Tph cells to the development of rheumatic and musculoskeletal diseases varies depending on each disease. In this review, we provide an overview of human Tfh and Tph cells and summarise the latest findings on these novel T cell subsets in various rheumatic and musculoskeletal diseases.

Disease-specific expansion of CD29+IL-17RA+ T effector cells possessing multiple signalling pathways in spondyloarthritis.

OBJECTIVES: T cells adhere to enthesis fibrocartilage via integrins and intrinsically require IL-17RA-mediated signals to maintain their effector function. We analysed CD29+IL-17RA+ T cells in inflamed lesions and peripheral blood in patients with SpA and investigated their association with disease activity and therapeutic response. METHODS: Transcriptome analysis of synovial fluid T cells from PsA was performed using publicly available bulk cell RNA sequencing data. Blood samples were obtained from healthy controls (n = 37), RA (n = 12), IgG4-related disease (IgG4-RD; n = 12), large vessel vasculitis (LVV; n = 12) and SpA (n = 28) and were analysed by flow cytometry. RESULTS: T cells in the inflamed joints of PsA showed CD29 and IL-17RA expression. CD29+IL-17RA+ T cells showed enriched CXCR3+CD45RA+ effector cells and activation of spleen tyrosine kinase (Syk), nuclear factor κB (NF-κB) and Janus kinase-signal transducer and activator of transcription (JAK-STAT) pathways. The proportion of peripheral blood CD29+IL-17RA+ T cells was significantly increased in patients with SpA compared with patients with RA, IgG4-RD or LVV and in healthy controls. Based on the ASDAS-CRP scores, the proportion of CD29+IL-17RA+ T cells was positively correlated with disease activity in treatment-naïve patients with active SpA. Anti-IL-17 but not anti-TNF monoclonal antibodies reduced CD29+IL-17RA+ T cells. CONCLUSIONS: CD29+IL-17RA+ T effector cells with enhanced Syk, NF-κB and JAK-STAT pathways were specifically increased in SpA and were correlated with disease activity, implicating a role of this newly identified T cell population in the pathogenesis. Anti-IL-17 monoclonal antibodies may be effective for patients by reducing this pathogenic T cell population.

Significant association of CX3CR1+CD8 T cells with aging and distinct clinical features in Sjögren's syndrome and IgG4-related disease.

OBJECTIVES: Recent studies have implicated cytotoxic CD4 and CD8 T cells in primary Sjögren's syndrome (pSS) and IgG4-related disease (IgG4-RD), but their association with immune aging and organ-specific clinical features remain unclear. CX3CR1 is expressed on cytotoxic CD4 and CD8 T cells. The aim of this study was to determine associations of peripheral CX3CR1+CD4 and CX3CR1+CD8 T cells with aging and clinical features. METHODS: Whole blood samples were freshly obtained from consecutive patients with active, treatment-naïve pSS (n=57), IgG4-RD (n=54), and healthy individuals (n=40) and analysed by flow cytometry for CX3CR1+CD4 and CX3CR1+CD8 proportions. Associations of those T cells with aging and clinical features were determined. RESULTS: CX3CR1+CD4 and CX3CR1+CD8 T cells selectively expressed perforin and granzyme B. Proportions of CX3CR1+CD4 and CX3CR1+CD8 T cells were significantly higher in pSS and IgG4-RD than in healthy individuals. Higher proportions of CX3CR1+CD8 T cells were associated with aging in pSS and IgG4-RD but not in healthy individuals. Sex differences were not associated with proportions of CX3CR1+CD8 T cells. Furthermore, patients with pSS with interstitial lung disease showed higher proportions of CX3CR1+CD8 T cells than those without interstitial lung disease. IgG4-RD patients with retroperitoneal fibrosis and/or aortitis exhibited higher proportions of CX3CR1+CD8 T cells compared with those with Mikulicz's disease. Moreover, proportions of CX3CR1+CD8 T cells were decreased following glucocorticoid treatment in paralleled with clinical improvements in IgG4-RD. CONCLUSIONS: CX3CR1+CD8 T cells might be involved in immune aging and distinct clinical phenotypes of patients with pSS or IgG4-RD.

Distinct impact of malignancy and allergy on the clinical and immunological features of IgG4-related disease.

OBJECTIVES: To clarify the clinical and immunological characteristics of IgG4-RD based on the underlying diseases. METHODS: Consecutive patients with IgG4-RD treated at Keio University Hospital between 2010 and 2021 were divided according to the presence of malignancy or allergy into three groups. The clinical characteristics and 56 immune cell subsets in the peripheral blood were compared among the groups. RESULTS: Among 123 patients, 18 (14.6%) had malignancy including 4 with allergy (malignancy group), 57 (46.3%) had allergy alone (allergy group), and 48 (39.0%) had neither (idiopathic group). In the malignancy group, the patients were older (70.1 vs. 54.4 vs. 64.9 years, p<0.001), male-dominant (83.3 vs. 42.1 vs. 54.2%, p=0.008), and had smoking habits (77.8 vs. 42.1 vs. 43.8%, p=0.02). They also had significant involvement of the aorta/large vessels (33.3 vs. 7.0 vs. 20.8%, p=0.02), while the patients in the allergy group tended to have orbital/lacrimal gland involvement. Remission and relapse rates were not different between the groups; however, overall survival was significantly poorer in the malignancy group (p=0.02). Comprehensive immunophenotyping of the peripheral blood revealed that the increase in CXCR5+CD2-double negative T cells and the decrease in naive CD8 T cells were characteristic of the malignancy group. CONCLUSIONS: The clinical and immunological phenotypes of IgG4-RD differ among those with underlying diseases.

Giant cell arteritis successfully treated with subcutaneous tocilizumab monotherapy.

Glucocorticoid remains the mainstay for treatment of large vessel vasculitis (LVV) including giant cell arteritis (GCA); however, the disease affects the elderly for whom the adverse effects of glucocorticoid are problematic. Recently, some reports have suggested that intravenous tocilizumab (TCZ) monotherapy is effective for this disease. To date, it remains unknown whether subcutaneous TCZ monotherapy is also effective. Here, we present a first case of GCA successfully treated with subcutaneous TCZ monotherapy. A 75-year-old woman presented with shoulder and hip pain. She was diagnosed with polymyalgia rheumatica (PMR) and treated with low-dose prednisolone (15 mg daily); however, she discontinued glucocorticoid therapy at her discretion due to the psychiatric adverse effect (cognitive dysfunction). Seven months later, her shoulder and hip pain relapsed. Furthermore, 18F-fluorodeoxyglucose (FDG)-positron emission tomography (PET)/computed tomography (CT) revealed uptake in the descending thoracic aorta, indicating a complication of LVV. She refused to take glucocorticoid for fear of psychiatric adverse effects and chose subcutaneous TCZ monotherapy (162 mg weekly) for treating this life-threatening urgent condition. Nine months later, her shoulder and hip pain resolved and FDG-PET/CT demonstrated no uptake in the descending thoracic aorta, indicating a successful treatment with subcutaneous TCZ monotherapy for the disease. No adverse events and disease relapse were found during observation period. Our case and the literature review suggest that not only intravenous injection but also subcutaneous injection of TCZ monotherapy can serve as an alternative treatment for patients with GCA who have comorbidities or refuse to take glucocorticoid.

Systematic review and meta-analysis for 2023 clinical practice guidelines of the Japan Research Committee of the Ministry of Health, Labour, and Welfare for Intractable Vasculitis for the management of ANCA-associated vasculitis.

OBJECTIVES: The objective of this study is to provide evidence for the revision of clinical practice guidelines for the management of antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis by the Japan Research Committee for Intractable Vasculitis. METHODS: PubMed, CENTRAL, and the Japan Medical Abstracts Society databases were searched for articles published between 2015 and 2020 to update the systematic review for existing clinical questions, while PubMed, CENTRAL, EMBASE, and the Japan Medical Abstracts Society were searched for articles published between 2000 and 2020 to conduct a systematic review for newly developed clinical questions. The certainty of evidence was assessed with the GRADE approach. RESULTS: For remission induction, when used in conjunction with cyclophosphamide or rituximab, reduced-dose glucocorticoid lowered the risk of serious adverse events compared to standard-dose glucocorticoid. Avacopan improved sustained remission at 12 months compared to high-dose glucocorticoid. Addition of plasma exchange to remission induction therapy did not reduce the risk of death, end-stage kidney disease, or relapse. For remission maintenance, rituximab reduced the risk of relapse compared to azathioprine. Long-term rituximab or azathioprine reduced the risk of relapse compared to short-term rituximab or azathioprine, respectively. CONCLUSIONS: This systematic review provided evidence required to develop the 2023 clinical practice guideline for the management of ANCA-associated vasculitis.

Immunoglobulin G4-related disease and idiopathic multicentric Castleman's disease: confusable immune-mediated disorders.

IgG4-related disease (IgG4-RD) and idiopathic multicentric Castleman's disease (iMCD) are both rare systemic immune-mediated disorders. However, the pathogenesis differs markedly between the two diseases and differing therapeutic strategies are adopted: IgG4-RD is treated using a moderate dose of glucocorticoids or rituximab, while iMCD therapy involves an IL-6-targeted approach. Nonetheless, some clinical features of IgG4-RD and iMCD overlap, so differential diagnosis is sometimes difficult, even though the classification and diagnostic criteria of the diseases require careful exclusion of the other. The key findings in IgG4-RD are high IgG4:IgG ratio, allergic features and germinal centre expansion involving T follicular helper cells, while iMCD involves polyclonal antibody production (high IgA and IgM levels), sheet-like mature plasma cell proliferation and inflammatory features driven by IL-6. The distribution of organ involvement also provides important clues in both diseases. Particular attention should be given to differential diagnosis using combined clinical and/or pathological findings, because single features cannot distinguish IgG4-RD from iMCD. In the present review, we discuss the similarities and differences between IgG4-RD and iMCD, as well as how to distinguish the two diseases.

Dropped head in systemic sclerosis: a case based review.

Dropped head syndrome is a rare disease entity characterized by severe weakness of the cervical para-spinal muscles, resulting in a chin-on-chest deformity. Systemic sclerosis is one of the causes of dropped head syndrome, but its characteristics and prognosis remain unclear due to the extreme rarity of this condition. We present a case of dropped head which occurred in systemic sclerosis. He presented with severe dropped head and relatively mild weakness of the proximal limb muscles. Serum level of creatine kinase was elevated, myopathic change was observed in electromyography, and gadolinium enhancement was found in magnetic resonance imaging of his posterior neck muscles. Anti-topoisomerase I antibody was positive, while other autoantibodies such as anti-PM/Scl and anti-Ku antibodies were negative. Since his dropped head acutely progressed, high dose of glucocorticoid therapy was initiated, which successfully improved dropped head, serum level of creatine kinase, and gadolinium enhancement in magnetic resonance imaging. Our present case and literature review suggest that dropped head occurring in systemic sclerosis can be treatable with immunosuppressive therapy. It is important to recognize this rare but treatable involvement of systemic sclerosis because early diagnosis and treatment initiation are crucial to prevent the irreversible organ damage and the significant decrease of daily activities.

Lymphadenopathy in IgG4-related disease: a phenotype of severe activity and poor prognosis, with eotaxin-3 as a new biomarker.

OBJECTIVE: To clarify relevant proteins and clinical characteristics of a phenotype of IgG4-related disease (IgG4-RD) with lymphadenopathy. METHODS: We enrolled patients newly diagnosed with IgG4-RD in our department between January 2000 and June 2018 and performed proteomic analysis to measure serum concentrations of 1305 proteins. We extracted proteins overexpressed in patients with IgG4-RD with lymphadenopathy by comparing between those with lymphadenopathy, those without lymphadenopathy and healthy controls. We further reviewed all the patients with IgG4-RD in our institution and investigated the characteristics and prognosis of the patients with IgG4-RD with lymphadenopathy. RESULTS: Eighty-five patients with IgG4-RD were enrolled, of which, 55% had lymphadenopathy. Proteomic analysis in 31 patients with IgG4-RD and 6 healthy controls revealed that eotaxin-3 was a potential serum biomarker in the patients with lymphadenopathy versus those without lymphadenopathy and healthy controls. A cohort of 85 patients with IgG4-RD demonstrated that patients with lymphadenopathy showed a significantly higher serum IgG4, IgG4:IgG ratio, IgG4-RD responder index and eosinophilia (P < 0.001 for all), irrelevant of the extent to which organ involvement developed. Patients with lymphadenopathy treated with glucocorticoid alone relapsed with significantly higher rates than those without lymphadenopathy (P = 0.03). CONCLUSION: Lymphadenopathy in IgG4-RD represents a phenotype associated with high disease activities, eosinophilia and relapsing disease. Eotaxin-3 is a novel biomarker related to IgG4-RD with lymphadenopathy.

[ALLERGIC DISEASES IN ADULT-ONSET STILL'S DISEASE AND RHEUMATOID ARTHRITIS].

BACKGROUND: A high prevalence of allergic diseases was found in patients with adult-onset Still's disease (AOSD). However, the relative prevalence is unknown compared with other diseases. OBJECTIVES: We sought to compare the prevalence of allergic diseases in the control group of patients with rheumatoid arthritis (RA). METHODS: We retrospectively examined consecutive patients diagnosed with AOSD or RA in our hospital from 2010 to 2020. The patients with AOSD met the preliminary criteria for classification of AOSD. The patients with RA met the EULAR/ACR 2010 criteria. We included patients with RA without other rheumatic diseases. The analysis was performed on six types of allergic reactions: food allergy, drug allergy, allergic contact dermatitis, allergic rhinitis and/or allergic conjunctivitis, and asthma. RESULTS: Twenty-four patients with AOSD and 409 patients with RA were enrolled. The median ages (AOSD, RA) were 46.6, 68.2 years old. Females were 83.3%, 78.0%. Fifty% of AOSD patients and 34.5% of RA patients presented at least one type of allergic diseases (p = 0.12). These included food allergy (4.2%, 6.4%: p = 1.0), drug allergy (37.5%, 16.6%: p = 0.02), allergic rhinitis/allergic conjunctivitis (25.0%, 8.6%: p = 0.02), contact dermatitis (4.2%, 4.4%: p = 1.0), and asthma (4.2%, 5.9%: p = 1.0). CONCLUSION: Patients with AOSD had a higher prevalence of drug allergy, and allergic rhinitis/allergic conjunctivitis than patients with RA.

Tocilizumab for the treatment of TAFRO syndrome: a systematic literature review.

TAFRO syndrome is a newly recognized disease entity characterized by thrombocytopenia, anasarca, fever, reticulin myelofibrosis, renal dysfunction, and organomegaly. The objective of this study was to investigate the effectiveness of tocilizumab, an anti-interleukin-6 receptor antibody, in patients with TAFRO syndrome. We performed a systematic literature review from inception to July 5, 2020, for articles reporting tocilizumab administration for the treatment of TAFRO syndrome. We identified 31 patients with TAFRO syndrome treated with tocilizumab. The mean age was 49.8 years, and 61.3% of the patients were male. The mean observation period was 12.6 months. Tocilizumab was used at the standard intravenous dose (8 mg/kg) weekly or every 2 weeks in combination with other immunosuppressive drugs, such as glucocorticoids, rituximab, cyclosporine, or cyclophosphamide, in most of the patients. Eighteen patients (58.1%) received tocilizumab as a first-line treatment, while it was a second-line or a third-line treatment for 13 patients with insufficient responses to the prior treatments. Sixteen patients (51.6%) obtained complete response to tocilizumab treatment, whereas 15 patients showed only partial or no response. Detailed factors of ineffectiveness included persistent thrombocytopenia (n = 7), persistent anasarca (n = 5), persistent renal dysfunction (n = 2), and persistent fever (n = 2). A total of four patients (12.9%) succumbed to the disease, while the remaining twenty-seven patients survived. Two patients achieved drug-free remission at last visit, and disease remission was maintained with tocilizumab monotherapy in five patients. No new safety signal was reported. Tocilizumab was effective in ~ 50% of the patients, suggesting it could serve as a treatment choice for TAFRO syndrome. Poor clinical response to tocilizumab observed in other patients highlights the need for the additional therapeutic treatment options.

Cytokines, growth factors and proteases in medium and large vessel vasculitis.

Giant cell arteritis and Takayasu arteritis are autoimmune vasculitides that cause aneurysm formation and tissue infarction. Extravascular inflammation consists of an intense acute phase response. Deeper understanding of pathogenic events in the vessel wall has highlighted the loss of tissue protective mechanisms, the intrusion of immune cells into "forbidden territory", and the autonomy of self-renewing vasculitic infiltrates. Adventitial vasa vasora critically control vessel wall access and drive differentiation of tissue-invasive T cells. Selected T cells establish tissue residency and build autonomous, self-sufficient inflammatory lesions. Pathogenic effector T cells intrude and survive due to failed immune checkpoint inhibition. Vasculitis-sustaining T cells and macrophages provide a broad portfolio of effector functions, involving heterogeneous populations of pro-inflammatory T cells and diverse macrophage subsets that ultimately induce wall capillarization and intimal hyperplasia. Redirecting diagnostic and therapeutic strategies from control of extravascular inflammatory markers to suppression of vascular inflammation will improve disease management.

Follicular helper T cells in the pathogenesis of IgG4-related disease.

IgG4-related disease (IgG4-RD) is a recently recognized disease entity characterized by high serum IgG4 concentrations and infiltration of IgG4+ plasma cells with hyperplastic ectopic germinal centres at affected sites. Although the underlying immune mechanism of this disease remains unclear, T cells are abundantly present at affected sites and key players in IgG4-RD pathogenesis. The role of T cell subsets has been investigated thoroughly in this disease. Recent advances in this field have clarified the importance of T follicular helper cells. In this review, we describe the role of T follicular helper cells in the disease process of IgG4-RD, in particular, for IgG4 class-switching, plasmablast and plasma cell differentiation, and germinal centre formation.

Interleukin-4 contributes to the shift of balance of IgG subclasses toward IgG4 in IgG4-related disease.

IgG4-related disease (IgG4-RD) is a systemic disorder characterized by elevated serum IgG4 level, which is mediated by T follicular helper 2 (Tfh2) cell. However, the cytokines responsible for enhancing IgG4 production remain unclear in IgG4-RD. The aim of this study was to identify responsible Tfh2-related cytokines (interleukin (IL)-4 and IL-21) for enhancing IgG4 production in IgG4-RD. Peripheral blood mononuclear cells obtained from consecutive patients with active, untreated IgG4-RD and healthy controls were examined. The production of both IgG and IgG4 were significantly increased by stimulation with IL-4 alone as well as IL-21 alone compared to background stimulation with anti-CD40 antibody in IgG4-RD. On the other hand, the IgG4/IgG ratio was statistically higher by stimulation with IL-4 alone compared to the other Tfh2-related cytokines including IL-21 in IgG4-RD. IgG4 production was not increased by stimulation with IL-4 in healthy controls. These results suggest that IL-4 can contribute to the shift of balance of IgG subclasses toward IgG4 compared to the other Tfh2-related cytokines in IgG4-RD.

Serum soluble interleukin-2 receptor is a useful biomarker for disease activity but not for differential diagnosis in IgG4-related disease and primary Sjögren's syndrome adults from a defined population.

OBJECTIVES: To identify biomarkers for disease activity in IgG4-related disease (IgG4-RD) and primary Sjögren's syndrome (pSS). METHODS: Forty-three consecutive treatment-naïve patients with IgG4-RD, 62 patients with pSS, and 5 patients with sicca syndrome were enrolled. IgG4-RD and pSS disease activity was assessed based on the IgG4-RD responder index (IgG4-RD RI) and EULAR Sjögren's Syndrome Disease Activity Index (ES- SDAI), respectively. The associations of biomarkers with disease activity were examined. RESULTS: Comparison of the three dis- eases identified the serum levels of IgG, IgG4, IgG4/IgG ratio, IgE, and soluble interleukin-2 receptor (sIL-2R) for IgG4-RD and the serum levels of IgM and sIL-2R and lymphocyte counts for pSS as potential biomarkers of disease activity. Among these, serum sIL-2R levels correlate with baseline IgG4-RD RI scores and the number of affected organs in IgG4-RD (ρ=0.74, p<0.0001 and ρ=0.75, p<0.0001, respectively). Serum sIL-2R levels also correlate with ESSDAI scores and the number of af- fected organs in pSS (ρ=0.67, p<0.0001 and ρ=0.41, p<0.0001, respectively). Receiver operating characteristic curve analysis suggested serum sIL-2R levels as an efficient biomarker to distinguish the presence of extra-dacryosialadenitis involvements in IgG4-RD with a cut-off value of 424 U/mL (AUC=0.93, p<0.0001), and in pSS with 452 U/mL (AUC=0.89, p<0.0001). Serum sIL-2R levels decreased significantly after treatment in patients with IgG4-RD and pSS. CONCLUSIONS: Serum sIL-2R levels are a potentially valuable biomarker for evaluating disease activity and treatment response in IgG4-RD and pSS.

Risk factors of relapse following glucocorticoid tapering in IgG4-related disease.

OBJECTIVES: To identify risk factors of relapse in IgG4-related disease (IgG4-RD) during glucocorticoid (GC) tapering. METHODS: A total of 27 consecutive patients with IgG4-RD (7 with and 20 without relapse) treated with GC for more than 6 months were enrolled. Baseline characteristics were compared in patients with and without relapse. Longitudinal analysis was also performed. RESULTS: Patients with relapse had significantly higher levels of serum IgG4 (816.0 vs. 346.5 mg/dL, p=0.048) and number of organs involved (5 vs. 3, p=0.008) and lower levels of serum IgA (82 vs. 176 mg/dL, p=0.002) at baseline, compared to patients without relapse. The most useful cut-off value of baseline serum IgG4 to predictive relapse was 813 mg/dl with a sensitivity of 57.1% and a specificity of 95.0%. In longitudinal analysis, serum IgG4 decreased at 6 months after treatment in both groups, but was elevated at relapse in patients with relapse, while remaining low in those without relapse. CONCLUSIONS: Higher levels of serum IgG4 at baseline were associated with relapse in IgG4-RD. Re-elevation of serum IgG4 levels during GC treatment reflected disease relapse.