Lymphoma Driver Mutations in the Pathogenic Evolution of an Iconic Human Autoantibody.

Pathogenic autoantibodies arise in many autoimmune diseases, but it is not understood how the cells making them evade immune checkpoints. Here, single-cell multi-omics analysis demonstrates a shared mechanism with lymphoid malignancy in the formation of public rheumatoid factor autoantibodies responsible for mixed cryoglobulinemic vasculitis. By combining single-cell DNA and RNA sequencing with serum antibody peptide sequencing and antibody synthesis, rare circulating B lymphocytes making pathogenic autoantibodies were found to comprise clonal trees accumulating mutations. Lymphoma driver mutations in genes regulating B cell proliferation and V(D)J mutation (CARD11, TNFAIP3, CCND3, ID3, BTG2, and KLHL6) were present in rogue B cells producing the pathogenic autoantibody. Antibody V(D)J mutations conferred pathogenicity by causing the antigen-bound autoantibodies to undergo phase transition to insoluble aggregates at lower temperatures. These results reveal a pre-neoplastic stage in human lymphomagenesis and a cascade of somatic mutations leading to an iconic pathogenic autoantibody.

In early rheumatoid arthritis, anticitrullinated peptide antibodies associate with low number of affected joints and rheumatoid factor associates with systemic inflammation.

OBJECTIVES: To investigate how individual rheumatoid arthritis (RA) autoantibodies associate with individual signs and symptoms at the time of RA diagnosis. METHODS: IgA, IgG, IgM rheumatoid factor (RF), antibodies against cyclic citrullinated peptide version 2 (anti-CCP2) and 16 individual antibodies against citrullinated protein (ACPA) reactivities were analysed centrally in baseline sera from 1600 patients with RA classified according to the 1987 American College of Rheumatology (ACR) criteria. These results were related to C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), number of swollen and tender joints (SJC and TJC), 28-joint disease activity scores (DAS28 and DAS28CRP), global disease activity evaluated by the patients and Health Assessment Questionnaire, all obtained at baseline. RESULTS: Individually, all autoantibodies except immunoglobulin G (IgG) RF associated with low SJC and TJC and with high ESR. In IgM RF-negative patients, ACPA associated strictly with low number of swollen and tender joints. This association persisted in multiple regression and stratified analyses where IgM and IgA RF instead associated with inflammation expressed as ESR. Among subjects without any ACPA peptide reactivity, there was no association between RF isotypes and ESR. The effect of RF on ESR increased with the number of ACPA reactivities, especially for IgM RF. In patients fulfilling the 1987 ACR criteria without taking RF into account, associations between IgM RF and high ESR, as well as between ACPA and low joint counts, remained. CONCLUSION: Whereas ACPA associate with low counts of affected joints in early RA, RF associates with elevated measures of systemic inflammation in an ACPA-dependent manner. This latter finding corroborates in vitro models of ACPA and RF in immune complex-induced inflammation. These phenotypic associations are independent of classification criteria.

Association of rheumatoid factor, anti-citrullinated protein antibodies and shared epitope with clinical response to initial treatment in patients with early rheumatoid arthritis: data from a randomised controlled trial.

OBJECTIVES: To investigate whether rheumatoid factor (RF), anti-citrullinated protein antibodies (ACPAs) and shared epitope (SE) allele-related genetic markers associate with treatment response to abatacept, certolizumab pegol or tocilizumab versus active conventional treatment (ACT). METHODS: Patients with treatment-naïve early rheumatoid arthritis were randomised in the NORD-STAR trial to ACT, certolizumab pegol, abatacept or tocilizumab, all with methotrexate. Centralised laboratory analyses for ACPA, RF and SE were performed. Clinical Disease Activity Index remission was analysed longitudinally with logistic generalised estimating equations. Differences in treatment effect across RF, ACPA and SE subgroups were assessed with interaction terms at 24 and 48 weeks, adjusted for sex, country, age, body mass index, Disease Activity Score of 28 joints based on C-reactive protein and smoking. RESULTS: In total, 778 patients were included. At 24 weeks, abatacept treatment showed a better response than ACT in the RF and/or ACPA-positive subgroups, but this effect was not significantly different from the negative subgroups. By 48 weeks, abatacept treatment showed better response regardless of RF/ACPA status. No differences were found across RF, ACPA, SE allele, valine at amino acid position 11 or valine-arginine-alanine haplotype subgroups for any biological treatment at 48 weeks. CONCLUSIONS: Based on this randomised controlled trial, abatacept treatment was associated with a better response than ACT in the RF and/or ACPA-positive subgroup at 24 weeks, but this was no longer seen at 48 weeks; adding SE allele-related genetic markers did not strengthen the association. Moreover, ACPA, RF and SE allele-related genotypes were not, alone or in combination, associated with clinical responses of importance sufficiently strongly to warrant implementation in clinical practice. TRIAL REGISTRATION NUMBER: EudraCT 2011-004720-35; ClinicalTrials.gov NCT01491815.

Early identification of rheumatoid arthritis: does it induce treatment-related cost savings?

OBJECTIVE: Early diagnosis and treatment-start is key for rheumatoid arthritis (RA), but the economic effect of an early versus a later diagnosis has never been investigated. We aimed to investigate whether early diagnosis of RA is associated with lower treatment-related costs compared with later diagnosis. METHODS: Patients with RA consecutively included in the Leiden Early Arthritis Clinic between 2011 and 2017 were studied (n=431). Symptom duration was defined as the time between symptom onset and first presentation at the outpatient clinic; early treatment start was defined as symptom duration <12 weeks. Information on disease-modifying anti-rheumatic drug use per patient over 5 years was obtained from prescription data from patient records. Prices were used from 2022 and 2012 (proxy of time of prescription) to study the impact of changes in drug costs. Autoantibody-positive and autoantibody-negative RA were studied separately because differences in disease severity may influence costs. RESULTS: Within autoantibody-negative RA, costs were 316% higher in the late compared with the early group (ß=4.16 (95% CI 1.57 to 11.1); €4856 vs €1159). When using 2012 prices, results were similar. For autoantibody-positive RA, costs were 19% higher in the late group (€9418 vs €7934, ß=1.19, 0.57 to 2.47). This effect was present but smaller when using 2012 prices. Within patients with autoantibody-positive RA using biologicals, late treatment start was associated with 46% higher costs (ß=1.46 (0.91 to 2.33)); higher costs were also seen when using 2012 prices. CONCLUSION: When RA is detected within 12 weeks after symptom onset, treatment-related costs were lower in both autoantibody-negative and autoantibody-positive RA. This study is the first to report how early diagnosis and treatment start impact treatment-related costs.

Novel and unique rheumatoid factors cross-react with viral epitopes in COVID-19.

Rheumatoid factors (RFs), polyreactive antibodies canonically known to bind two conformational epitopes of IgG Fc, are a hallmark of rheumatoid arthritis but also can arise in other inflammatory conditions and infections. Also, infections may contribute to the development of rheumatoid arthritis and other autoimmune diseases. Recently, RFs only in rheumatoid arthritis were found to bind novel linear IgG epitopes as well as thousands of other rheumatoid arthritis autoantigens. Specific epitopes recognized by infection-induced polyreactive RFs remain undefined but could provide insights into loss of immune tolerance. Here, we identified novel linear IgG epitopes bound by RFs in COVID-19 but not rheumatoid arthritis or other conditions. The main COVID-19 RF was polyreactive, binding two IgG and multiple viral peptides with a tripeptide motif, as well as IgG Fc and SARS-CoV-2 spike proteins. In contrast, a rheumatoid arthritis-specific RF recognized IgG Fc, but not tripeptide motif-containing peptides or spike. Thus, RFs have disease-specific IgG reactivity and distinct polyreactivities that reflect the broader immune response. Moreover, the polyreactivity of a virus-induced RF appears to be attributable to a very short peptide motif. These findings refine our understanding of RFs and provide new insights into how viral infections may contribute to autoimmunity.

The impact of autoantibodies on the efficacy of biological disease-modifying anti-rheumatic drugs in rheumatoid arthritis: meta-analysis of randomized controlled trials.

OBJECTIVE: To investigate the efficacy of bDMARDs in patients with RA with RF/ACPA compared with patients without these autoantibodies. METHODS: Previous systematic literature reviews performed by EULAR RA management task forces were searched for qualifying RCTs. RCTs investigating the efficacy of bDMARDs and including both autoantibody-positive (≤80% of total population) and -negative RA patients were eligible. For trials comparing bDMARD+csDMARD vs csDMARD, relative risks (RR) comparing two groups (RF + vs RF-, ACPA+ vs ACPA-) were calculated for efficacy outcomes for each arm. Subsequently, relative risk ratios (RRRs) were computed, as the ratio of RR of the bDMARD-arm and the RR from the non-bDMARD-arm. Pooled effects were obtained with random effect meta-analyses. RESULTS: Data from 28 eligible RCTs were analyzed, pooling 23 studies in three subgroups: 6 including csDMARD-naïve patients, 14 csDMARD-IR, and 3 TNFi-IR patients. In csDMARD-naïve and csDMARD-IR patients, seropositivity was not associated with a better response to bDMARDs: pooled 6-month ACR20 RRRs 1.02 (0.88-1.18) and 1.09 (0.90-1.32), respectively. Other outcomes showed no difference between groups either. In TNFi-IR patients, based on 3 trials, the 6-month ACR20 RRR was 2.28 (1.31-3.95), favoring efficacy in seropositive patients. Other outcomes mostly showed no significant difference between the groups. Based on the mode of action, efficacy was comparable between RF-positive and RF-negative patients for both TNFi and non-TNFi treatment and also for the individual bDMARDs. CONCLUSION: The effect of bDMARDs is generally comparable in patients with and without RF/ACPA, regardless of the patient population, the mechanism of action or individual drug used.

Are the cut-offs of the rheumatoid factor and anti-cyclic citrullinated peptide antibody different to distinguish rheumatoid arthritis from their primary differential diagnoses?

OBJECTIVE: Rheumatoid factor (RF) and anti-cyclic citrullinated peptide antibody (anti-CCP) are commonly used for diagnosis of rheumatoid arthritis (RA), although other rheumatic diseases with arthritis can test positive. This study aimed to determine the cutoff values for RF and anti-CCP with the best diagnostic performance in a sample of patients with RA, compared with other rheumatic diseases. METHODS: This was a descriptive, prospective study. EUROINMMUN enzyme-linked immunosorbent assays for RF isotypes immunoglobulin (Ig) A (IgA), IgG and IgM and third-generation assay IgG for anti-CCP were used in serum samples of patients with RA, other rheumatic diseases and healthy subjects. The cutoff with the best diagnostic performance was determined by the Youden Index and receiver operating characteristic analysis Results: Three hundred and thirty-two serum samples were analysed. The cutoffs proposed in our population were for RF in RA patients versus other rheumatic diseases, and healthy subjects IgM 135 IU/mL, for each disease, compared with RA, were psoriatic arthritis (Psa) IgA 47.2 IU/mL, clinically suspicious arthralgia (CSA) IgA 39.5 IU/mL, primary Sjögren's syndrome (pSS) IgM 180.6 IU/mL, systemic lupus erythematosus (SLE) IgA 42.6 IU/mL, primary fibromyalgia (pFM) IgM 68.6 IU/mL, osteoarthritis (OA) IgM 48 IU/mL, gout IgM 117 IU/mL and healthy IgM 16.3 IU/mL. For anti-CCP, in RA patients versus other rheumatic diseases, and healthy subjects 6.95 IU/mL, for each disease, compared with RA, were Psa 6.8 IU/mL, CSA 9.95 IU/mL, pSS 20.7 IU/mL, SLE 6 IU /mL, pFM 11.8 IU/mL, OA 11.9 IU/mL, gout 5 IU/mL and healthy 5 IU/mL. CONCLUSION: Irrespective of the manufacturer's suggested cutoff, the RA versus differential diagnosis cutoffs must be considered.

Exploring the Link between Hydrodynamic Size and Immunoglobulins of Circulating Immune Complexes in Rheumatoid Arthritis Patients.

The function of immune complexes in rheumatoid arthritis (RA) is related to their composition and size. Using dynamic light scattering (DLS), we investigated the link between the RA circulating immune complex (CIC) particles' size and the CIC immunoglobulin level. In this study, 30 RA patients and 30 healthy individuals were included. IgA, IgG, and IgM were found in all analyzed CICs, but more IgA and IgG were found in RA than in control CICs. In both control and RA CICs, DLS detected 50 particles that differed in size and clustered around two size groups: with a 7.5-164 nm radius and with a 342-1718 nm radius. An increased level of IgA in RA CICs, compared to control ones, was associated with more than 50% of CIC particles. In RA, compared to the control, a higher number of CICs with 28.2 nm, 531 nm, 712 nm, and 1718 nm particles and a lower number of CICs with 78.8 nm particles were detected. This particle distribution pattern did not reflect the changes in the CIC immunoglobulin level. Thus, RA elevated CIC IgA was linked with all these particles (except the 1718 nm particle), the IgM increase was linked with 43.8 nm and 712 nm particles, and the IgG increase was linked with the 712 nm particle only. This study provides the very first data on the association between CIC particles' size, CIC immunoglobulin level, and RA. It opens the possibility that the size of CICs determined by DLS can be used as a criterion in RA diagnosis or monitoring after a large-scale study confirmation.

Complete Description of the Three Pathways of the Complement System in a Series of 430 Patients with Rheumatoid Arthritis.

The complement (C) system is implicated in the etiopathogenesis of rheumatoid arthritis (RA). However, there is a lack of studies characterizing all three C pathways in RA patients. This study aimed to evaluate the association between an in-depth examination of the C system and RA patient characteristics, focusing on disease activity and the presence of rheumatoid factor and anti-citrullinated protein autoantibodies (ACPA). In a cohort of 430 RA patients, functional assays of the three C pathways (classical, alternative, and lectin) and serum levels of their components were assessed. Components included C1q (classical); factor D and properdin (alternative); lectin (lectin); C1-inhibitor; C2, C4, and C4b (classical and lectin); C3, C3a, and C4b (common); and C5, C5a, and C9 (terminal). A multivariable linear regression analysis showed significant positive correlations between C-reactive protein and C system proteins and functional assays, especially in the terminal and common pathways. Disease activity, measured by scores with or without acute phase reactants, positively correlated with the classical pathway functional test and terminal pathway products. Conversely, rheumatoid factor or ACPA presence was associated with lower classical pathway values and decreased C3a and C4b levels, suggesting complement depletion. In conclusion, RA disease activity increases C molecules and functional complement assays, while rheumatoid factor or ACPA positivity is linked to C consumption. Our study offers a detailed analysis of the complement system's role in RA, potentially guiding the development of more targeted and effective treatment strategies.

Lung inflammation in the pathogenesis of rheumatoid arthritis.

The primary manifestation of rheumatoid arthritis (RA) is articular disease; however, extra-articular disease can also occur. In particular, pulmonary disease is a leading cause of morbidity and mortality in individuals with RA. Herein, we will review the types, prevalence, risk factors, and potential pathophysiology of lung disease in individuals with established RA. We will also discuss the emerging understanding of potential role of the lung in the generation of RA-related autoantibodies during a period of disease development termed "pre-RA." Finally, we will discuss a research agenda outlining the next steps to improve our understanding and management of lung inflammation and lung disease throughout the natural history of RA.

Clinical Utility of Pro-inflammatory Oligomeric Glycoprotein Tenascin-C in the Diagnosis of Seropositive and Seronegative Rheumatoid Arthritis.

Owing to limited usefulness of Rheumatoid Factor and anti-CCP in rheumatoid arthritis, there is a need to identify a more sensitive and specific biomarker to detect rheumatoid arthritis (RA), particularly seronegative RA cases. Tenascin-C is an extracellular matrix glycoprotein, which has been implicated in the pathophysiology of RA. The objective of our study was to evaluate the diagnostic utility of serum Tenascin-C in seropositive and seronegative rheumatoid arthritis patients. We conducted a cross-sectional case control study. Sixty patients who fulfilled the ACR 2010 criteria for rheumatoid arthritis were included in the study. Thirty patients were found to be positive for RF and/or anti-CCP and 30 were negative for both RF and anti-CCP. Thirty age and gender-matched healthy subjects were taken as controls. Serum Tenascin-C was measured by quantitative sandwich enzyme immunoassay technique. The mean serum concentration of Tenascin-C in controls, seronegative and seropositive cases was 0.66 ng/ml, 20.54 ng/ml and 23.42 ng/ml, respectively. Tenascin-C levels were significantly higher in RA cases compared to controls (p < 0.0001). There was no significant difference in Tenascin-C between seropositive and seronegative cases (p = 0.603). ROC curve analysis showed a sensitivity of 96.6% and specificity of 100% with AUC of 0.98 at 2.21 ng/ml as cut-off value for diagnosing RA. Tenascin-C is elevated in both seronegative and seropositive RA, which indicates that it can be used as a sensitive marker for RA. The addition of Tenascin-C to the existing RF and anti-CCP may help in identifying a large number of patients with RA, particularly seronegative rheumatoid arthritis cases.

Association Between Rheumatic Autoantibodies and Immune-Related Adverse Events.

BACKGROUND: Side effects of immune checkpoint inhibitors (ICIs), called immune-related adverse events (irAEs), closely resemble primary autoimmune or rheumatic diseases. We aimed to understand the clinical utility of rheumatic autoantibodies (rhAbs) for diagnosing irAEs. PATIENTS AND METHODS: Patients without pre-existing autoimmune disease (pAID) who had cancer treated with ICI(s) treatment from 1/1/2011 to 12/21/2020 and a rhAb checked were retrospectively identified. Logistic regression assessed associations between autoantibodies and irAEs, cancer outcome, and survival. Specificity, sensitivity, and positive/negative predictive values (PPV, NPV) were estimated for key rhAbs and ICI-arthritis. Kaplan-Meier analyzed objective response rate (ORR) and overall survival (OS). RESULTS: A total of 2662 patients were treated with≥1 ICIs. One hundred and thirty-five without pAID had ≥ 1 rhAb tested. Of which 70/135(52%) were female; median age at cancer diagnosis was 62 years with most common cancers: melanoma (23%) or non-small cell lung cancer (21%), 96/135 (75%) were anti-PD1/PDL1 treated. Eighty had a rhAb ordered before ICI, 96 after ICI, and 12 before and after. Eighty-two (61%) experienced an irAE, 33 (24%) with rheumatic-irAE. Pre-ICI RF showed significant association with rheumatic-irAEs (OR = 25, 95% CI, 1.52-410.86, P = .024). Pre- and post-ICI RF yielded high specificity for ICI-arthritis (93% and 78%), as did pre- and post-ICI CCP (100% and 91%). Pre-ICI RF carried 93% NPV and pre-ICI CCP had 89% PPV for ICI-arthritis. No variables were significantly correlated with ORR. Any-type irAE, rheumatic-irAE and ICI-arthritis were all associated with better OS (P = .000, P = .028, P = .019). CONCLUSIONS: Pre-ICI RF was associated with higher odds of rheumatic-irAEs. IrAEs had better OS; therefore, clinical contextualization for rhAbs is critical to prevent unnecessary withholding of lifesaving ICI for fear of irAEs.

Rheumatoid factor autoantibody repertoire profiling reveals distinct binding epitopes in health and autoimmunity.

BACKGROUND: Rheumatoid factors (RF) are one of the hallmark autoantibodies characteristic of rheumatoid arthritis (RA), and are frequently observed in other diseases and in healthy individuals. RFs comprise multiple subtypes with different specificities towards the constant region of human IgG. Studies indicate that these patterns differ between naturally occurring RFs and RFs associated with disease. However, individual specificities characteristic of either have not been clearly defined. METHODS: In this study, we developed an extended set of engineered IgG-fragment crystallisable (Fc) targets with preferential RF binding to specific (conformational) epitopes, which was subsequently used for profiling of RF binding patterns in a compiled exploration cohort, consisting of sera from healthy donors with measurable RF and patients with RA, primary Sjögren's syndrome (pSS) and seropositive arthralgia. RESULTS: We identified an epitope that is strongly associated with RA, which was targeted by both IgM-RF and IgA-RF. We also identified an epitope that is preferentially targeted by healthy donor (IgM) RFs. IgM-RFs derived from healthy donors and patients with RA and pSS all target distinct regions on the IgG-Fc, whereas overall, the IgA-RF repertoire is largely restricted to pathology-associated specificities. Using monoclonal RFs with different specificities, we furthermore demonstrate that the capacity to activate complement or even inhibit IgG-mediated complement activation varies according to the epitopes to which RFs bind. CONCLUSIONS: Our results demonstrate both the need and feasibility to redefine 'RF' into pathological and physiological autoantibody subtypes.

Interleukin 4-driven reversal of self-reactive B cell anergy contributes to the pathogenesis of systemic lupus erythematosus.

OBJECTIVES: Reactivation of anergic autoreactive B cells (BND cells) is a key aetiological process in systemic lupus erythematosus (SLE), yet the underlying mechanism remains largely elusive. This study aimed to investigate how BND cells participate in the pathogenesis of SLE and the underlying mechanism. METHODS: A combination of phenotypical, large-scale transcriptome and B cell receptor (BCR) repertoire profiling were employed at molecular and single cell level on samples from healthy donors and patients with SLE. Isolated naïve B cells from human periphery blood were treated with anti-CD79b mAb in vitro to induce anergy. IgM internalisation was tracked by confocal microscopy and was qualified by flow cytometer. RESULTS: We characterised the decrease and disruption of BND cells in SLE patients and demonstrated IL-4 as an important cytokine to drive such pathological changes. We then elucidated that IL-4 reversed B cell anergy by promoting BCR recycling to the cell surface via STAT6 signalling. CONCLUSIONS: We demonstrated the significance of IL-4 in reversing B cell anergy and established the scientific rationale to treat SLE via blocking IL-4 signalling, also providing diagnostic and prognostic biomarkers to identify patients who are most likely going to benefit from such treatments.

Annals of the Rheumatic Diseases collection on autoantibodies in the rheumatic diseases: new insights into pathogenesis and the development of novel biomarkers.

The rheumatic diseases are a diverse group of conditions that can display autoantibody production, functional immune disturbances and systemic disease manifestations. These autoantibodies can serve as markers for classification, diagnosis, prognosis and disease activity. Among specificities prominently expressed by patients, those directed to nuclear antigens (antinuclear antibodies or ANAs) are markers for specific rheumatic diseases. ANAs can bind to DNA, RNA and complexes of proteins with nucleic acids. Other autoantibodies expressed in the rheumatic diseases are directed to proteins, including IgG, post-translational modifications of proteins and soluble mediators such as cytokines. While autoantibodies have been investigated for over 50 years, recent studies published in the Annals of the Rheumatic Diseases (ARD) have provided an exciting perspective on the mechanisms of autoantibody production and the power of new technologies to identify novel autoantibody targets to elucidate aetiology and underpin patient evaluation. Furthermore, in-depth serological studies have demonstrated a phenomenon known as clustering; clustering defines sets of autoantibodies that are commonly expressed together in patients with a given rheumatic disease. Other research reported in ARD has used B cell phenotyping and genotypic analysis to subtype patients, and has explored the relationship of autoantibodies, complement activation and patterns of gene expression as exemplified by the interferon gene signature. Together, these studies provide important new insights into disease mechanisms as well as actionable information to facilitate personalised patient care.

Irreversible covalent Bruton's tyrosine kinase inhibitor, TAS5315 versus placebo in rheumatoid arthritis patients with inadequate response to methotrexate: a randomised, double-blind, phase IIa trial.

OBJECTIVE: To examine the efficacy and safety of TAS5315, an irreversible covalent Bruton's tyrosine kinase inhibitor, in Japanese patients with rheumatoid arthritis (RA) refractory to methotrexate. METHODS: In part A of this phase IIa double-blind study, patients were randomised to TAS5315 4 or 2 mg or placebo once daily for 12 weeks; in part B, all patients received TAS5315 for another 24 weeks. The proportion of patients meeting American College of Rheumatology criteria for 20% improvement (ACR20) at week 12 was assessed (primary endpoint). RESULTS: Ninety-one patients were randomised in part A, and 84 entered part B. At week 12, 78.9% of patients achieved ACR20 in the TAS5315 combined group vs 60.0% with placebo (p=0.053), 33.3% vs 13.3% achieved ACR50 (p=0.072) and 7.0% vs 0.0% achieved ACR70 (p=0.294), respectively. More patients receiving TAS5315 than placebo had low disease activity or remission at week 12. Clinical and biomarker improvements were maintained during part B. Adverse event (AE) incidence in TAS5315 was similar to placebo in part A; common AEs with TAS5315 were nasopharyngitis (10.3%), pruritus (6.9%) and cystitis (5.2%). Over 36 weeks, nine patients experienced bleeding events of whom four and two patients recovered with drug continuation and interruption, respectively. Three patients recovered after TAS5315 discontinuation. CONCLUSIONS: The primary endpoint was not achieved. TAS5315 appears to have some bleeding risks, but nevertheless demonstrated numerical differences, compared with placebo, in the improvement rates of all measures of RA disease activity. Future analysis of the risk-benefit of TAS5315 should be considered. TRIAL REGISTRATION NUMBERS: NCT03605251, JapicCTI-184020, jRCT2080223962.

Autoimmune markers and vascular immune deposits in Finkelstein-Seidlmayer vasculitis: Systematic literature review.

Finkelstein-Seidlmayer vasculitis, also called acute hemorrhagic edema of young children or infantile immunoglobulin A vasculitis, is habitually a benign skin-limited small vessel leukocytoclastic vasculitis that mainly affects infants 24 months or less of age. Since this disease is commonly triggered by an infection, an immune-mediated origin has been postulated. To better appreciate the possible underlying immune mechanism of this vasculitis, we addressed circulating autoimmune markers and vascular immune deposits in patients contained in the Acute Hemorrhagic Edema BIbliographic Database, which incorporates all original reports on Finkelstein-Seidlmayer vasculitis. A test for at least one circulating autoimmune marker or a vascular immune deposit was performed in 243 cases. Subunits of complement system C4 resulted pathologically reduced in 4.7% and C3 in 1.4%, rheumatoid factor was detected in 6.1%, and antinuclear antibodies in 1.9% of cases. Antineutrophil cytoplasmic antibodies were never demonstrated. Immunofluorescence studies were performed on 125 skin biopsy specimens and resulted positive for complement subunits in 46%, fibrinogen in 45%, immunoglobulin A in 25%, immunoglobulin M in 24%, immunoglobulin G in 13%, and immunoglobulin E in 4.2% of cases. Infants testing positive for vascular immunoglobulin A deposits did not present a higher prevalence of systemic involvement or recurrences, nor a longer disease duration. In conclusion, we detected a very low prevalence of circulating autoimmune marker positivity in Finkelstein-Seidlmayer patients. Available immunofluorescence data support the notion that immune factors play a relevant role in this vasculitis. Furthermore, vascular immunoglobulin A deposits seem not to play a crucial role in this disease.

Serum calprotectin correlates more strongly with inflammation and disease activity in ACPA positive than ACPA negative rheumatoid arthritis.

OBJECTIVES: The aim of the present study was to evaluate performance of serum and synovial fluid levels of the granulocyte protein calprotectin as inflammatory biomarker in rheumatoid arthritis (RA) patients with knee synovitis. METHODS: 76 RA patients with ongoing knee synovitis were included. Data on disease activity score with 28 joints and their subcomponents and radiological destruction of the affected knee were collected. White blood cell count, C-reactive protein, anti-citrullinated peptide antibodies (ACPA) against cyclic citrullinated peptide version 2 (anti-CCP2), IgM rheumatoid factor (RF) and calprotectin were analysed in parallel in circulation and in synovial fluid (SF). Counts of polynuclear and mononuclear cells were measured in SF. RESULTS: Serum (S) calprotectin correlated stronger than SF-calprotectin with inflammatory markers and disease activity. Instead, SF-calprotectin showed a strong correlation to SF counts of white blood cells, and especially to polymorphonuclear cell counts (Spearman's rho = 0.72, p< 0.001). S-calprotectin showed markedly stronger correlation with inflammatory markers and disease activity in ACPA positive as compared with ACPA negative RA patients; a similar difference was observed for patients with and without IgM RF. CONCLUSION: The particularly strong association between circulating calprotectin and inflammation in ACPA positive RA is a new argument for a specific role for polymorphonuclear granulocytes/neutrophils in this RA subset. Measurement of calprotectin in SF does not convey any additional benefit compared with measurement in the circulation in RA patients with knee synovitis.

Value of diagnosing immunological phenomena in patients with suspected endocarditis.

PURPOSE: Immunological phenomena are a minor criteria in the modified Duke Criteria for endocarditis. Given the changes in epidemiology and diagnostics, the added value of determining these phenomena in today's patients with suspected endocarditis is unknown. METHODS: In a retrospective cohort study of all patients with suspected endocarditis admitted to our hospital and discussed in our endocarditis team, we determined the proportion of patients classified as definite endocarditis because of either positive IgM rheumatoid factor (IgM RF), haematuria, or Roth's spots on ophthalmology consultation. We also determined diagnostic accuracy of each of these immunological phenomena separately and combined. RESULTS: Of 285 patients included, 138 (48%) had definite endocarditis and at least one immunological test was performed in 222 patients (78%). Elevated IgM RF was found in 22 of 126 patients tested (17%), haematuria in 78 of 196 tested (40%) and Roth's spots in six of 120 tested (5%). Eighteen of 138 patients with definite IE (13%) were classified as such because of a positive IgM RF, haematuria or Roth's spots. Haematuria had the highest sensitivity: 50.5% (95% CI 40.4-60.6) and Roth's spots the highest specificity: 98.3% (95% CI 90.8-99.9). The diagnostic accuracy results were robust in a sensitivity analysis aimed at avoiding incorporation bias. CONCLUSION: Among patients with a clinical suspicion of endocarditis, recommended systematic testing for immunological phenomena helped classify more patients as definite IE and is useful to confirm the diagnosis of endocarditis.

Regulatory Rheumatoid Factor is Specific to PD-1 and Uses PD-1 Pathway to Control CD4 T Lymphocytes.

BACKGROUND: We have earlier discovered a new factor of autoimmunity downregulation, called regulatory rheumatoid factor (regRF). Being anti-idiotypic antibodies, regRF restricts the expansion of CD4+ T lymphocytes to the idiotype of which it is specific, according to the negative feedback principle. It has been shown that only activated CD4+ T lymphocytes are the target of regRF. However, it is still not clear the way regRF distinguishes activated cells from naive ones. RegRF molecules, apart from individual paratopes specific to unique sequences of B- and T-cell receptors, have a shared paratope. We assume that regRF by means of a shared paratope recognizes one of the surface activation molecules of CD4+ T lymphocytes and initiates the cell death. Programmed death-1 (PD-1) has been tested as a potential receptor of the shared regRF paratope and transmitter of the negative regRF signal into activated CD4+ T lymphocytes. METHODS: The specificity of the shared regRF paratope to PD-1 was determined by ELISA. T cell activation was performed with immobilized anti-CD3ε antibodies. Flow cytometry was used to study the effect of regRF on PD-1+CD4+ lymphocytes. RESULTS: We found that regRF binds to PD-1. IgG Fc fragments carrying epitopes specific to the shared paratope of regRF compete with PD-1 for binding to regRF. It follows that regRF recognizes specifically PD-1 by means of a shared paratope. RegRF-containing serum reduced the number of PD-1+CD4+ lymphocytes in proportion to their increase resulting from the action of anti-CD3ε antibodies. CONCLUSION: RegRF uses PD-1 pathway to control activated CD4+ T lymphocytes.