Peptide targeting improves the delivery and therapeutic index of glucocorticoids to treat rheumatoid arthritis

Rheumatoid arthritis (RA) is a prevalent autoimmune disease characterized by excessive inflammation in the joints. Glucocorticoid drugs are used clinically to manage RA symptoms, while their dosage and duration need to be tightly controlled due to severe adverse effects. Using dexamethasone (DEX) as a model drug, we explored here whether peptide-guided delivery could increase the safety and therapeutic index of glucocorticoids for RA treatment. Using multiple murine RA models such as collagen-induced arthritis (CIA), we found that CRV, a macrophage-targeting peptide, can selectively home to the inflammatory synovium of RA joints upon intravenous injection. The expression of the CRV receptor, retinoid X receptor beta (RXRB), was also elevated in the inflammatory synovium, likely being the basis of CRV targeting. CRV-conjugated DEX increased the accumulation of DEX in the inflamed synovium but not in healthy organs of CIA mice. Therefore, CRV-DEX demonstrated a stronger efficacy to suppress synovial inflammation and alleviate cartilage/bone destruction. Meanwhile, CRV conjugation reduced immune-related adverse effects of DEX even after a long-term use. Last, we found that RXRB expression was significantly elevated in human patient samples, demonstrating the potential of clinical translation. Taken together, we provide a novel, peptide-targeted strategy to improve the therapeutic efficacy and safety of glucocorticoids for RA treatment.

Profibrotic VEGFR3-Dependent Lymphatic Vessel Growth in Autoimmune Valvular Carditis

BACKGROUND

Rheumatic heart disease is the major cause of valvular heart disease in developing nations. Endothelial cells (ECs) are considered crucial contributors to rheumatic heart disease, but greater insight into their roles in disease progression is needed.

METHODS

We used a Cdh5-driven EC lineage-tracing approach to identify and track ECs in the K/B.g7 model of autoimmune valvular carditis. Single-cell RNA sequencing was used to characterize the EC populations in control and inflamed mitral valves. Immunostaining and conventional histology were used to evaluate lineage tracing and validate single-cell RNA-sequencing findings. The effects of VEGFR3 (vascular endothelial growth factor receptor 3) and VEGF-C (vascular endothelial growth factor C) inhibitors were tested in vivo. The functional impact of mitral valve disease in the K/B.g7 mouse was evaluated using echocardiography. Finally, to translate our findings, we analyzed valves from human patients with rheumatic heart disease undergoing mitral valve replacements.

RESULTS

Lineage tracing in K/B.g7 mice revealed new capillary lymphatic vessels arising from valve surface ECs during the progression of disease in K/B.g7 mice. Unsupervised clustering of mitral valve single-cell RNA-sequencing data revealed novel lymphatic valve ECs that express a transcriptional profile distinct from other valve EC populations including the recently identified PROX1 (Prospero homeobox protein 1)+ lymphatic valve ECs. During disease progression, these newly identified lymphatic valve ECs expand and upregulate a profibrotic transcriptional profile. Inhibiting VEGFR3 through multiple approaches prevented expansion of this mitral valve lymphatic network. Echocardiography demonstrated that K/B.g7 mice have left ventricular dysfunction and mitral valve stenosis. Valve lymphatic density increased with age in K/B.g7 mice and correlated with worsened ventricular dysfunction. Importantly, human rheumatic valves contained similar lymphatics in greater numbers than nonrheumatic controls.

CONCLUSIONS

These studies reveal a novel mode of inflammation-associated, VEGFR3-dependent postnatal lymphangiogenesis in murine autoimmune valvular carditis, with similarities to human rheumatic heart disease.

HLA-DRB1*15 and Eosinophilia Are Common Among Patients With Systemic Juvenile Idiopathic Arthritis

OBJECTIVE

Concern exists that medications used to treat patients with systemic juvenile idiopathic arthritis (JIA), particularly interleukin (IL)-1 and IL-6 blocking agents, might be causing adverse drug reactions and lung disease (systemic JIA-LD). Carriage of HLA-DRB1*15 has been reported as a risk factor for adverse drug reactions among patients with systemic JIA. We performed a retrospective chart review to evaluate these factors at our center.

METHODS

We reviewed the records of 86 subjects with systemic JIA followed for at least 6 months between 1996 and 2022. HLA typing was performed in 23 of the subjects. We compared characteristics of patients with or without eosinophilia. Among patients with HLA typing, we compared clinical characteristics of subjects with or without DRB1*15 and with or without systemic JIA-LD.

RESULTS

Among the 23 patients with HLA typing, 74% carried DRB1*15, and 63% of patients without systemic JIA-LD carried DRB1*15. Seven subjects had systemic JIA-LD, all of whom carried DRB1*15. Patients with systemic JIA-LD were younger at the time of diagnosis and more likely to have had macrophage activation syndrome. Exposure to IL-1 and IL-6 blockers was common, occurring in 95% of patients. Eosinophilia occurred in 39% of patients with systemic JIA, often before IL-1 or IL-6 blockade. Eosinophilia was associated with adverse drug reactions and macrophage activation syndrome. There was 1 death, unrelated to active systemic JIA disease.

CONCLUSION

Carriage of DRB1*15 was more common in this cohort of patients with systemic JIA than in the general population. Eosinophilia and systemic JIA-LD were more common among patients with severe systemic JIA complicated by macrophage activation syndrome.

Aortic Stenosis Risk in Rheumatoid Arthritis

Importance

Although an increased risk of ischemic cardiovascular disease has been associated with rheumatoid arthritis (RA), the risk of aortic stenosis (AS) is unknown.

Objective

To examine the risk of incident AS, aortic valve intervention, AS-related death, and risk factors for AS development in patients with RA.

Design, Setting, and Participants

This cohort study linked data from the Veterans Health Administration (VHA) and Centers for Medicare & Medicaid Services from 2000 to 2019. Patients with RA were matched by age, sex, and VHA enrollment year with up to 10 patients without RA. The cohort was followed until incident AS, aortic valve intervention, or death. Data were analyzed from August 23, 2022, to March 3, 2023.

Exposures

the primary exposure was the presence of RA, defined using validated RA algorithms.

Main Outcomes and Measures

Aortic stenosis was defined as a composite of inpatient or outpatient diagnoses, surgical or transcatheter aortic valve replacement, or AS-related death using diagnostic and procedural codes. Risk of AS development was assessed with multivariable Cox proportional hazards models adjusted for race, ethnicity, smoking status, body mass index, rurality, comorbidities, and health care use.

Results

The cohort included 73 070 patients with RA (64 008 [87.6%] males; mean [SD] age, 63.0 [11.9] years) matched with 639 268 patients without RA (554 182 [86.7%] males; mean [SD] age, 61.9 [11.7] years) and 16 109 composite AS outcomes that occurred over 6 223 150 person-years. The AS incidence rate was 3.97 (95% CI, 3.81-4.13) per 1000 person-years in patients with RA and 2.45 (95% CI, 2.41-2.49) per 1000 person-years in the control patients (absolute difference, 1.52 per 1000 person-years). Rheumatoid arthritis was associated with an increased risk of composite AS (adjusted hazard ratio [AHR], 1.48; 95% CI, 1.41-1.55), aortic valve intervention (AHR, 1.34; 95% CI, 1.22-1.48), and AS-related death (AHR, 1.26; 95% CI, 1.04-1.54).

Conclusions and Relevance

In this cohort study, RA was associated with a higher risk of developing AS and the subsequent risks of undergoing aortic valve intervention and suffering from AS-related death. Future studies are needed to confirm whether valvular heart disease, specifically AS, may be an overlooked cardiovascular disease complication in RA.

Autoimmune Valvular Carditis Requires Endothelial Cell TNFR1 Expression

BACKGROUND

Inflammation is a key driver of cardiovascular pathology, and many systemic autoimmune/rheumatic diseases are accompanied by increased cardiac risk. In the K/B.g7 mouse model of coexisting systemic autoantibody-mediated arthritis and valvular carditis, valve inflammation depends on macrophage production of TNF (tumor necrosis factor) and IL-6 (interleukin-6). Here, we sought to determine if other canonical inflammatory pathways participate and to determine whether TNF signaling through TNFR1 (tumor necrosis factor receptor 1) on endothelial cells is required for valvular carditis.

METHODS

We first asked if type 1, 2, or 3 inflammatory cytokine systems (typified by IFNγ, IL-4, and IL-17, respectively) were critical for valvular carditis in K/B.g7 mice, using a combination of in vivo monoclonal antibody blockade and targeted genetic ablation studies. To define the key cellular targets of TNF, we conditionally deleted its main proinflammatory receptor, TNFR1, in endothelial cells. We analyzed how the absence of endothelial cell TNFR1 affected valve inflammation, lymphangiogenesis, and the expression of proinflammatory genes and molecules.

RESULTS

We found that typical type 1, 2, and 3 inflammatory cytokine systems were not required for valvular carditis, apart from a known initial requirement of IL-4 for autoantibody production. Despite expression of TNFR1 on a wide variety of cell types in the cardiac valve, deleting TNFR1 specifically on endothelial cells protected K/B.g7 mice from valvular carditis. This protection was accompanied by reduced expression of VCAM-1 (vascular cell adhesion molecule), fewer valve-infiltrating macrophages, reduced pathogenic lymphangiogenesis, and diminished proinflammatory gene expression.

CONCLUSIONS

TNF and IL-6 are the main cytokines driving valvular carditis in K/B.g7 mice. The interaction of TNF with TNFR1 specifically on endothelial cells promotes cardiovascular pathology in the setting of systemic autoimmune/rheumatic disease, suggesting that therapeutic targeting of the TNF:TNFR1 interaction could be beneficial in this clinical context.

Prolonged Elevations of Factor VIII and von Willebrand Factor Antigen After Multisystem Inflammatory Syndrome in Children

Multisystem Inflammatory Syndrome in Children (MIS-C) is a late systemic inflammatory response to a recent mild or asymptomatic coronavirus disease of 2019 infection. The pathophysiology is incompletely understood but it often features significant coagulopathy along with cardiac and endothelial dysfunction. Endothelial inflammation has been primarily described in acute coronavirus disease of 2019 infection, with less characterization in MIS-C. Here we describe novel findings of nearly universal severe and prolonged factor VIII (FVIII) and von Willebrand factor antigen elevations in an institutional cohort of patients with MIS-C ages younger than or 21 years old (N=31). All patients had elevated acute phase reactants and D-dimer at presentation and met published criteria for MIS-C. FVIII was high at presentation in 97% of patients but continued to rise during the ensuing weeks of treatment to a mean 429%, peaking on median day 17 of illness as an outpatient. FVIII levels were >600% in multiple patients. von Willebrand factor antigen was measured less frequently but showed similar trends. These escalations occurred amidst resolving cardiac dysfunction and acute phase reactant normalization and despite patients receiving multimodal anti-inflammatory treatments and aspirin and enoxaparin thromboprophylaxis. No thrombotic events occurred. Endothelial dysfunction represented by very elevated FVIII levels may persist longer than other acute phase reactants may reflect.

Capturing critical data elements in Juvenile Idiopathic Arthritis: initiatives to improve data capture

BACKGROUND

Documentation of critical data elements is a focus of the Pediatric Rheumatology Care and Outcomes Improvement Network to aid in clinical care and research for patients with juvenile idiopathic arthritis. We aimed to increase data capture for critical data elements and hypothesized that quality improvement methodology would improve data capture. We also hypothesized that data capture for all critical data elements would be lower for virtual visits compared to in-person visits.

METHODS

All visits for patients with JIA between 9/14/2020 and 12/31/2021 at the University of Minnesota were included. We assessed completeness of critical data element capture. Sixteen interventions with providers were conducted, including email reminders, individual discussions, group meetings, and feedback reports. We used statistical process control charts to evaluate change over time.

RESULTS

Baseline included 355 patient-visits: 221 (62%) in-person and 134 (38%) virtual with critical data elements entry ranging between 50 and 60%. Post-intervention included 1,596 patient-visits: 1,350 (85%) in-person and 246 (15%) virtual, with critical data elements entry reaching 91%. All providers improved data entry during this study. In-person visits had significantly higher data capture rates than virtual visits for all 4 critical data elements.

CONCLUSION

We achieved our aim to increase critical data element documentation by focusing on provider buy-in, frequent reminders, and individualized feedback. We also found that collection of critical data elements occurred significantly less often with virtual visits than with in-person visits. Now that we improved capture of critical data elements, we can shift the focus to efforts aimed at improving outcomes for patients with juvenile arthritis.

Non-criteria antiphospholipid antibodies and pediatric rheumatic disease: a case series

BACKGROUND

Non-criteria antiphospholipid antibodies (NC-aPL) are a relatively undefined subgroup of antiphospholipid antibodies (aPL). Knowledge about NC-aPL in adults is limited and even less is known in pediatric patients. Routine tests for antiphospholipid syndrome (APS)-a clinical state marked by the presence of aPL in association with vascular thrombosis-usually include lupus anticoagulant (LAC), anti-cardiolipin (aCL) and -beta-2 glycoprotein I (aβ2GPI). LAC is a functional screen for prothrombotic aPL, while the latter tests identify specific autoantibodies. Specific targets of NC-aPL include, but are not limited to, phosphatidylethanolamine, phosphatidylserine, and prothrombin.

PRESENTATION OF CASES

We present single-center data from eight pediatric patients with NC-aPL identified during a three-year period. All patients had presenting features raising suspicion for APS. Most patients were female with a primary rheumatic disease. One patient had a stroke. Another patient had alveolar hemorrhage and pulmonary hypertension. Raynaud's phenomenon, rashes involving distal extremities, and headaches were common. Most patients had a positive LAC, yet their routine aPL tests were negative, prompting testing for NC-aPL.

CONCLUSIONS

Our findings suggest NC-aPL are associated with typical signs and symptoms of APS in pediatric patients. Pediatricians and pediatric subspecialists should consider NC-aPL when clinical suspicion is high and routine aPL tests are negative, particularly when LAC is positive. While guidelines for NC-aPL do not yet exist for children or adults, these autoantibodies have pathogenic potential. Actionable items could include evaluation for the presence of other (primary) rheumatic diseases, and consultation with hematologists and/or obstetricians regarding anticoagulation/platelet inhibition and thrombosis education. Future guidelines regarding NC-aPL will only be generated by gathering more data, ideally prospectively.

The Conundrum of Lung Disease and Drug Hypersensitivity-like Reactions in Systemic Juvenile Idiopathic Arthritis

An unusual form of lung disease has begun to affect some children with systemic juvenile idiopathic arthritis (JIA), coincident with increasing utilization of interleukin-1 (IL-1) and IL-6 antagonists. Many children with systemic JIA-associated lung disease (SJIA-LD) have a history of clinical and laboratory features resembling drug reaction with eosinophilia and systemic symptoms (DRESS), a presentation now convincingly associated with HLA-DRB1*15. Treatment of DRESS typically requires drug discontinuation, a daunting prospect for clinicians and families who rely upon these agents. Here we review SJIA-LD and its associated DRESS-like phenotype. We suggest an alternative explanation, the cytokine plasticity hypothesis, proposing that IL-1 and IL-6 blockers modulate the milieu in which T cells develop, leading to a pathologic immune response triggered through exposure to common microbes, or to other exogenous or endogenous antigens, rather than to the drugs themselves. This hypothesis differs from DRESS in mechanism but also in clinical implications, predicting that control of pathogenic T cells could permit continued use of IL-1 and IL-6 antagonists in some individuals. The spectrum posed by these two hypotheses provides a conceptual framework that will guide investigation into the pathogenesis of SJIA-LD and may open up new therapeutic avenues for patients with systemic JIA.

CD47 Promotes Autoimmune Valvular Carditis by Impairing Macrophage Efferocytosis and Enhancing Cytokine Production

Systemic autoantibody-mediated diseases accelerate chronic cardiovascular disease in humans. In the K/B.g7 mouse model of spontaneous autoantibody-mediated inflammatory arthritis, valvular carditis arises in part because of Fc receptor-mediated activation of macrophages, leading to production of pathogenic TNF and IL-6. In this study, we explored whether impaired efferocytosis mediated by the interaction of CD47-expressing apoptotic cells with signal regulatory protein α (SIRPα) on macrophages contributes to disease progression in this model. CD47-expressing apoptotic cells and SIRPα⁺ macrophages were abundant in inflamed/rheumatic cardiac valves from both mice and humans. In vivo anti-CD47 blockade both prevented and treated valvular carditis in K/B.g7 mice. Blocking CD47 enhanced macrophage efferocytosis and reduced macrophage production of TNF and IL-6. These studies highlight the CD47:SIRPα interaction as a key driver of chronic cardiac valve inflammation and suggest these molecules as potential therapeutic targets to reduce cardiovascular disease risk in autoantibody-driven inflammatory diseases.

A dominant function of LynB kinase in preventing autoimmunity

Here, we report that the LynB splice variant of the Src-family kinase Lyn exerts a dominant immunosuppressive function in vivo, whereas the LynA isoform is uniquely required to restrain autoimmunity in female mice. We used CRISPR-Cas9 gene editing to constrain lyn splicing and expression, generating single-isoform LynA knockout (LynAKO) or LynBKO mice. Autoimmune disease in total LynKO mice is characterized by production of antinuclear antibodies, glomerulonephritis, impaired B cell development, and overabundance of activated B cells and proinflammatory myeloid cells. Expression of LynA or LynB alone uncoupled the developmental phenotype from the autoimmune disease: B cell transitional populations were restored, but myeloid cells and differentiated B cells were dysregulated. These changes were isoform-specific, sexually dimorphic, and distinct from the complete LynKO. Despite the apparent differences in disease etiology and penetrance, loss of either LynA or LynB had the potential to induce severe autoimmune disease with parallels to human systemic lupus erythematosus (SLE).

2021 American College of Rheumatology/Vasculitis Foundation Guideline for the Management of Kawasaki Disease

OBJECTIVE

To provide evidence-based recommendations and expert guidance for the management of Kawasaki disease (KD), focusing on clinical scenarios more commonly addressed by rheumatologists.

METHODS

Sixteen clinical questions regarding diagnostic testing, treatment, and management of KD were developed in the Patient/Population, Intervention, Comparison, and Outcomes (PICO) question format. Systematic literature reviews were conducted for each PICO question. We used the Grading of Recommendations, Assessment, Development and Evaluation method to assess the quality of evidence and formulate recommendations. Each recommendation required consensus from at least 70% of the Voting Panel.

RESULTS

We present 1 good practice statement, 11 recommendations, and 1 ungraded position statement to guide the management of KD and clinical scenarios of suspected KD. These recommendations for KD are focused on situations in which input from rheumatologists may be requested by other managing specialists, such as in cases of treatment-refractory, severe, or complicated KD. The good practice statement affirms that all patients with KD should receive initial treatment with intravenous immunoglobulin (IVIG). In addition, we developed 7 strong and 4 conditional recommendations for the management of KD or suspected KD. Strong recommendations include prompt treatment of incomplete KD, treatment with aspirin, and obtaining an echocardiogram in the setting of unexplained macrophage activation syndrome or shock. Conditional recommendations include use of IVIG with other adjuvant agents for patients with KD and high-risk features of IVIG resistance and/or coronary artery aneurysms. These recommendations endorse minimizing risk to the patient by using established therapy promptly at disease onset and identifying situations in which adjunctive therapy may be warranted.

CONCLUSION

These recommendations provide guidance regarding diagnostic strategies, use of pharmacologic agents, and use of echocardiography in patients with suspected or confirmed KD.

2021 American College of Rheumatology/Vasculitis Foundation Guideline for the Management of Kawasaki Disease

OBJECTIVE

To provide evidence-based recommendations and expert guidance for the management of Kawasaki disease (KD), focusing on clinical scenarios more commonly addressed by rheumatologists.

METHODS

Sixteen clinical questions regarding diagnostic testing, treatment, and management of KD were developed in the Patient/Population, Intervention, Comparison, and Outcomes (PICO) question format. Systematic literature reviews were conducted for each PICO question. We used the Grading of Recommendations, Assessment, Development and Evaluation method to assess the quality of evidence and formulate recommendations. Each recommendation required consensus from at least 70% of the Voting Panel.

RESULTS

We present 1 good practice statement, 11 recommendations, and 1 ungraded position statement to guide the management of KD and clinical scenarios of suspected KD. These recommendations for KD are focused on situations in which input from rheumatologists may be requested by other managing specialists, such as in cases of treatment-refractory, severe, or complicated KD. The good practice statement affirms that all patients with KD should receive initial treatment with intravenous immunoglobulin (IVIG). In addition, we developed 7 strong and 4 conditional recommendations for the management of KD or suspected KD. Strong recommendations include prompt treatment of incomplete KD, treatment with aspirin, and obtaining an echocardiogram in the setting of unexplained macrophage activation syndrome or shock. Conditional recommendations include use of IVIG with other adjuvant agents for patients with KD and high-risk features of IVIG resistance and/or coronary artery aneurysms. These recommendations endorse minimizing risk to the patient by using established therapy promptly at disease onset and identifying situations in which adjunctive therapy may be warranted.

CONCLUSION

These recommendations provide guidance regarding diagnostic strategies, use of pharmacologic agents, and use of echocardiography in patients with suspected or confirmed KD.

Using quality improvement methodology and tools to reduce patient wait time in a paediatric subspecialty rheumatology clinic

Our paediatric rheumatology clinic has experienced inefficient patient flow. Our aim was to reduce mean wait time and minimise variation for patients. Baseline data showed that most waiting occurs after a patient has been roomed, while waiting for the physician. Wait time was not associated with a patient's age, time of day, day of the week or individual physician. We implemented a checkout sheet and staggered start times. After a series of plan-do-study-act cycles, we observed an initial 26% reduction in the variation of wait time and a final 17% reduction in the mean wait time. There was no impact on patient-physician contact time. Overall, we demonstrate how process improvement methodology and tools were used to reduce patient wait time in our clinic, adding to the body of literature on process improvement in an ambulatory setting.

Anti-MDA5 juvenile idiopathic inflammatory myopathy with second-degree heart block but no skin or lung involvement: a case report

Background

Patients with idiopathic inflammatory myopathy and autoantibodies directed against melanoma differentiation-associated protein 5 (MDA5) characteristically have interstitial lung disease, severe cutaneous involvement, arthritis, and relatively mild myositis. Cardiac involvement in idiopathic inflammatory myopathy can occur and has been associated with anti-signal recognition particle and anti-polymyositis-scleroderma autoantibodies, but not with anti-MDA5 autoantibodies.

Case presentation

A 14-year-old male presented with weakness, second-degree heart block, arthritis, and hematologic cytopenias. Imaging and biopsies confirmed the diagnosis of juvenile idiopathic inflammatory myopathy, and he had high titer anti-MDA5 autoantibodies. There were no cutaneous or pulmonary abnormalities. While on prednisone and methotrexate, the patient’s heart block improved from second- to first-degree and the cytopenias resolved. Persistent myositis prompted the addition of intravenous immunoglobulin. Seven months into the disease course, the arthritis and myositis are in remission and the patient is no longer taking corticosteroids.

Conclusions

We report a novel case of a patient with juvenile idiopathic myositis who lacked the typical cutaneous and pulmonary findings associated with anti-MDA5 positivity, but who had cardiac conduction defects. This report broadens the clinical spectrum of anti-MDA5-associated inflammatory myopathy.

Case Report: A Novel TNFAIP3 Mutation Causing Haploinsufficiency of A20 With a Lupus-Like Phenotype

Genetic mutations that result in loss-of-function of the protein A20 result in an early-onset autoinflammatory disease—haploinsufficiency of A20 (HA20). The reported clinical presentations of HA20 include a Behcet’s disease-like phenotype and a more lupus-like phenotype. We have identified a novel mutation in the gene encoding A20 in a pediatric patient with chronic lymphadenopathy, lupus-like symptoms, and progressive hypogammaglobulinemia. This case illustrates the wide range of clinical symptoms, including immunodeficiency, that can occur in patients with HA20.

Rapid Infliximab Infusion in the Pediatric Population

OBJECTIVES

To compare infusion reaction rates between rapid infliximab (REMICADE, Janssen Biotech Inc) infusions and previous standard 2- to 3-hour infusions; additionally, to assess patient satisfaction and reduction in chair time associated with rapid infliximab infusions.

METHODS

Pediatric rheumatology and gastroenterology patients receiving maintenance infliximab therapy using a standard 2- to 3-hour titrated infusion had the opportunity to enroll in the non-titrated rapid 1-hour infusion protocol following tolerance of induction dosing at 0, 2, and 6 weeks. Patients were included from December 1, 2017, to March 31, 2018, via retrospective chart review and patient satisfaction surveys.

RESULTS

Data were collected on 55 patients receiving a total of 160 rapid infliximab infusions. There were 2 infusion reactions during the enrollment and data collection period, resulting in an overall infusion reaction rate of 1.3%. The patient satisfaction survey results showed all patients were at minimum satisfied with the information provided regarding rapid infliximab, decreased time spent in clinic, ease of scheduling, and overall process.

CONCLUSIONS

Our data suggest rapid infliximab infusions are safe in pediatric rheumatology and gastroenterology patients receiving maintenance infliximab infusion therapy. The overall infusion reaction rate of 1.3% in this study is well below the accepted infusion reaction rate of standard-length infliximab infusions of 2% to 3%.

T cell-intrinsic role for Nod2 in protection against Th17-mediated uveitis

Mutations in nucleotide-binding oligomerization domain-containing protein 2 (NOD2) cause Blau syndrome, an inflammatory disorder characterized by uveitis. The antimicrobial functions of Nod2 are well-established, yet the cellular mechanisms by which dysregulated Nod2 causes uveitis remain unknown. Here, we report a non-conventional, T cell-intrinsic function for Nod2 in suppression of Th17 immunity and experimental uveitis. Reconstitution of lymphopenic hosts with Nod2^-/- CD4⁺ T cells or retina-specific autoreactive CD4⁺ T cells lacking Nod2 reveals a T cell-autonomous, Rip2-independent mechanism for Nod2 in uveitis. In naive animals, Nod2 operates downstream of TCR ligation to suppress activation of memory CD4⁺ T cells that associate with an autoreactive-like profile involving IL-17 and Ccr7. Interestingly, CD4⁺ T cells from two Blau syndrome patients show elevated IL-17 and increased CCR7. Our data define Nod2 as a T cell-intrinsic rheostat of Th17 immunity, and open new avenues for T cell-based therapies for Nod2-associated disorders such as Blau syndrome.

Noninvasive ultrasound stimulation of the spleen to treat inflammatory arthritis

Targeted noninvasive control of the nervous system and end-organs may enable safer and more effective treatment of multiple diseases compared to invasive devices or systemic medications. One target is the cholinergic anti-inflammatory pathway that consists of the vagus nerve to spleen circuit, which has been stimulated with implantable devices to improve autoimmune conditions such as rheumatoid arthritis. Here we report that daily noninvasive ultrasound (US) stimulation targeting the spleen significantly reduces disease severity in a mouse model of inflammatory arthritis. Improvements are observed only with specific parameters, in which US can provide both protective and therapeutic effects. Single cell RNA sequencing of splenocytes and experiments in genetically-immunodeficient mice reveal the importance of both T and B cell populations in the anti-inflammatory pathway. These findings demonstrate the potential for US stimulation of the spleen to treat inflammatory diseases.

Autoantibodies in the Pathogenesis, Diagnosis, and Prognosis of Juvenile Idiopathic Arthritis

Autoantibody production occurs in juvenile idiopathic arthritis (JIA) and numerous other autoimmune diseases. In some conditions, the autoantibodies are clearly pathogenic, whereas in others the roles are less defined. Here we review various autoantibodies associated with JIA, with a particular focus on antinuclear antibodies and antibodies recognizing citrullinated self-antigens. We explore potential mechanisms that lead to the development of autoantibodies and the use of autoantibody testing in diagnosis and prognosis. Finally, we compare and contrast JIA-associated autoantibodies with those found in adults with rheumatoid arthritis (RA).

A bivalent compound targeting CCR5 and the mu opioid receptor treats inflammatory arthritis pain in mice without inducing pharmacologic tolerance

Background

Pain accompanies rheumatoid arthritis and other chronic inflammatory conditions and is difficult to manage. Although opioids provide potent analgesia, chronic opioid use can cause tolerance and addiction. Recent studies have demonstrated functional interactions between chemokine and opioid receptor signaling pathways. Reported heterodimerization of chemokine and opioid receptors led our group to develop bivalent compounds that bind both types of receptors, with the goal of targeting opioids to sites of inflammation. MCC22 is a novel bivalent compound containing a CCR5 antagonist and mu opioid receptor (MOR) agonist pharmacophores linked through a 22-atom spacer. We evaluated the efficacy of MCC22 in the K/B.g7 T-cell receptor transgenic mouse model of spontaneous inflammatory arthritis.

Methods

MCC22 or morphine was administered intraperitoneally at varying doses to arthritic K/B.g7 mice or nonarthritic control mice. Mechanical pain hypersensitivity was measured each day before and after drug administration, using the electronic von Frey test. The potency of MCC22 relative to that of morphine was calculated. Functional readouts of pain included grip strength and nesting behavior. A separate dosing regimen was used to determine whether the drugs induced pharmacologic tolerance.

Results

MCC22 provided ~ 3000-fold more potent analgesia than morphine in this model. Daily treatment with MCC22 also led to a cumulative analgesic effect, reducing the daily baseline pain level. MCC22 produced no observable analgesic effect in nonarthritic control mice. Importantly, repeated administration of MCC22 did not induce pharmacologic tolerance, whereas a similar regimen of morphine did. Both grip strength and nesting behaviors improved among arthritic mice treated with MCC22. Ankle thickness and arthritis scores were not affected by MCC22. The analgesic effect of MCC22 was abolished in K/B.g7 mice genetically lacking CCR5, demonstrating the receptor specificity of the antagonist pharmacophore.

Conclusions

MCC22 is a novel bivalent ligand that targets CCR5 and MOR. Our findings demonstrate that MCC22 provides highly potent analgesia and improved functional outcomes in a model of inflammatory arthritis, without inducing typical opioid tolerance. These findings suggest that MCC22 or similar compounds could be used to treat the pain associated with inflammatory arthritis and related conditions, while minimizing the risks typically associated with chronic opioid use.

Electronic supplementary material

The online version of this article (10.1186/s13075-018-1661-5) contains supplementary material, which is available to authorized users.

Inflammatory arthritis in pediatric patients with morphea

BACKGROUND

Morphea or localized scleroderma is an inflammatory disorder resulting in fibrosis of the skin and subcutaneous tissues. Joint contractures, arthralgias, and functional compromise are recognized associations of pediatric morphea. The co-existence of inflammatory arthritis and morphea is not well-described in the literature.

OBJECTIVE

To investigate the relationship between pediatric morphea and inflammatory arthritis with regards to cutaneous, musculoskeletal, and laboratory findings and treatment regimens.

METHODS

A systematic retrospective chart review of 53 patients with pediatric morphea was performed and analyzed for morphea subtypes, arthritic joint involvement, serum autoantibodies, and therapeutic interventions.

RESULTS

Eleven out of 53 patients had polyarthritis that involved joints unrelated to the site of the cutaneous morphea. These patients were mostly girls with either the linear or generalized subtypes of morphea. Serum levels of antinuclear antibodies were more significantly elevated in patients with arthritis. All children were treated with methotrexate in addition to other systemic or topical immunosuppressive agents.

LIMITATIONS

This was a small, single-center retrospective study.

CONCLUSION

Pediatric morphea co-existed with inflammatory arthritis in 11 of 53 children. Further understanding and appreciation of this relationship may direct more intensive therapy and musculoskeletal screening.

The Contribution of Autoantibodies to Inflammatory Cardiovascular Pathology

Chronic inflammation and resulting tissue damage underlie the vast majority of acquired cardiovascular disease (CVD), a general term encompassing a widely diverse array of conditions. Both innate and adaptive immune mechanisms contribute to chronic inflammation in CVD. Although maladies, such as atherosclerosis and cardiac fibrosis, are commonly conceptualized as disorders of inflammation, the cellular and molecular mechanisms that promote inflammation during the natural history of these diseases in human patients are not fully defined. Autoantibodies (AAbs) with specificity to self-derived epitopes accompany many forms of CVD in humans. Both adaptive/induced iAAbs (generated following cognate antigen encounter) and also autoantigen-reactive natural antibodies (produced independently of infection and in the absence of T cell help) have been demonstrated to modulate the natural history of multiple forms of CVD including atherosclerosis (atherosclerotic cardiovascular disease), dilated cardiomyopathy, and valvular heart disease. Despite the breadth of experimental evidence for the role of AAbs in CVD, there is a lack of consensus regarding their specific functions, primarily due to disparate conclusions reached, even when similar approaches and experimental models are used. In this review, we seek to summarize the current understanding of AAb function in CVD through critical assessment of the clinical and experimental evidence in this field. We additionally highlight the difficulty in translating observations made in animal models to human physiology and disease and provide a summary of unresolved questions that are critical to address in future studies.

CD301b/MGL2+ Mononuclear Phagocytes Orchestrate Autoimmune Cardiac Valve Inflammation and Fibrosis

BACKGROUND

Valvular heart disease is common and affects the mitral valve (MV) most frequently. Despite the prevalence of MV disease (MVD), the cellular and molecular pathways that initiate and perpetuate it are not well understood.

METHODS

K/B.g7 T-cell receptor transgenic mice spontaneously develop systemic autoantibody-associated autoimmunity, leading to fully penetrant fibroinflammatory MVD and arthritis. We used multiparameter flow cytometry, intracellular cytokine staining, and immunofluorescent staining to characterize the cells in inflamed K/B.g7 MVs. We used genetic approaches to study the contribution of mononuclear phagocytes (MNPs) to MVD in this model. Specifically, we generated K/B.g7 mice in which either CX3CR1 or CD301b/macrophage galactose N-acetylgalactosamine-specific lectin 2 (MGL2)-expressing MNPs were ablated. Using K/B.g7 mice expressing Cx3Cr1-Cre, we conditionally deleted critical inflammatory molecules from MNPs, including the Fc-receptor signal-transducing tyrosine kinase Syk and the cell adhesion molecule very late antigen-4. We performed complementary studies using monoclonal antibodies to block key inflammatory molecules. We generated bone marrow chimeric mice to define the origin of the inflammatory cells present in the MV and to determine which valve cells respond to the proinflammatory cytokine tumor necrosis factor (TNF). Finally, we examined specimens from patients with rheumatic heart disease to correlate our findings to human pathology.

RESULTS

MNPs comprised the vast majority of MV-infiltrating cells; these MNPs expressed CX3CR1 and CD301b/MGL2. Analogous cells were present in human rheumatic heart disease valves. K/B.g7 mice lacking CX3CR1 or in which CD301b/MGL2-expressing MNPs were ablated were protected from MVD. The valve-infiltrating CD301b/MGL2⁺ MNPs expressed tissue-reparative molecules including arginase-1 and resistin-like molecule α. These MNPs also expressed the proinflammatory cytokines TNF and interleukin-6, and antibody blockade of these cytokines prevented MVD. Deleting Syk from CX3CR1-expressing MNPs reduced their TNF and interleukin-6 production and also prevented MVD. TNF acted through TNF receptor-1 expressed on valve-resident cells to increase the expression of vascular cell adhesion molecule-1. Conditionally deleting the vascular cell adhesion molecule-1 ligand very late antigen-4 from CX3CR1-expressing MNPs prevented MVD.

CONCLUSIONS

CD301b/MGL2⁺ MNPs are key drivers of autoimmune MVD in K/B.g7 mice and are also present in human rheumatic heart disease. We define key inflammatory molecules that drive MVD in this model, including Syk, TNF, interleukin-6, very late antigen-4, and vascular cell adhesion molecule-1.

Brief Report: Arthritis in KRN T Cell Receptor-Transgenic Mice Does Not Require Interleukin-17 or Th17 Cells

OBJECTIVE

Th17 cells and interleukin-17 (IL-17) cytokine family members are implicated in the pathogenesis of many rheumatic diseases. Most studies in mouse models of inflammatory arthritis have demonstrated a key role for the proinflammatory cytokine IL-17A and its receptor, the IL-17 receptor (IL-17R) A/C heterodimer. The aim of this study was to use a rigorous genetic approach to evaluate the contribution of Th17 cells and IL-17 in the autoantibody-dependent KRN T cell receptor-transgenic mouse model of arthritis.

METHODS

We bred KRN mice expressing the major histocompatibility complex class II molecule A(g7) (referred to as K/B/g7 mice) and genetically lacking the related cytokines IL-17A and IL-17F or their critical receptor subunit, IL-17RA. Using bone marrow transplantation, we generated mice in which hematopoietic cells from K/B/g7 donor mice lacked the key Th17-differentiating transcription factor, retinoic acid receptor-related orphan nuclear receptor γt (Rorγt).

RESULTS

K/B/g7 mice lacking both IL-17A and IL-17F produced normal titers of pathogenic autoantibodies, and arthritis developed in a typical manner. Similarly, neither IL-17RA nor Rorγt expression by hematopoietic cells was required for disease development in this model.

CONCLUSION

Despite prior reports suggesting that Th17 cells and IL-17A are crucially involved in the pathogenesis of arthritis in K/BxN mice, the results presented here provide genetic evidence that IL-17A and IL-17F, IL-17RA, and Rorγt expression by hematopoietic cells are dispensable for normal arthritis progression in the K/B/g7 mouse model system. We discuss potential explanations for the discrepancies between these 2 highly similar model systems. These findings plus those in other mouse models of arthritis provide insight regarding why therapeutic biologic agents targeting the Th17/IL-17 axis are beneficial in some human rheumatic diseases but not others.

Cutting Edge: Dual TCRα Expression Poses an Autoimmune Hazard by Limiting Regulatory T Cell Generation

Despite accounting for 10-30% of the T cell population in mice and humans, the role of dual TCR-expressing T cells in immunity remains poorly understood. It has been hypothesized that dual TCR T cells pose an autoimmune hazard by allowing self-reactive TCRs to escape thymic selection. We revisited this hypothesis using the NOD murine model of type 1 diabetes. We bred NOD mice hemizygous at both TCRα and β (TCRα^+/- β^+/-) loci, rendering them incapable of producing dual TCR T cells. We found that the lack of dual TCRα expression skewed the insulin-specific thymocyte population toward greater regulatory T (T_reg) cell commitment, resulting in a more tolerogenic T_reg to conventional T cell ratio and protection from diabetes. These data support a novel hypothesis by which dual TCR expression can promote autoimmunity by limiting agonist selection of self-reactive thymocytes into the T_reg cell lineage.

Use of Rheumatology Laboratory Studies Among Primary Pediatricians

Rheumatology laboratory tests are often inappropriately ordered in situations for which they are of low diagnostic utility. We surveyed pediatricians to investigate reasons for ordering these tests. The response rate was 15.3% (93/609). The most commonly ordered tests were antinuclear antibody (ANA), anti-double-stranded DNA (dsDNA) antibody, and rheumatoid factor (RF). Of the 89% (83/93) who ordered an ANA, 86% ordered it for correct/possibly correct reasons; of the 73% (68/93) who ordered RF, 80% did so for correct/possibly correct reasons; and among the 59% (54/92) who had ordered anti-dsDNA antibody, 34% ordered it for correct reasons. A positive relationship was seen between years since residency completion and correct use of ANA. However, positive associations were not seen between measures of pediatric rheumatology experience and correct use of other tests. Interventions are needed to improve pediatricians' utilization of rheumatology tests.

Bi-Allelic TCRα or β Recombination Enhances T Cell Development but Is Dispensable for Antigen Responses and Experimental Autoimmune Encephalomyelitis

Dual TCRα-expressing T cells outnumber dual TCRβ-expressing cells by ~10:1. As a result, efforts to understand how dual TCR T cells impact immunity have focused on dual TCRα expression; dual TCRβ expression remains understudied. We recently demonstrated, however, that dual TCRβ expression accelerated disease in a TCR transgenic model of autoimmune arthritis through enhanced positive selection efficiency, indicating that dual TCRβ expression, though rare, can impact thymic selection. Here we generated mice hemizygous for TCRα, TCRβ, or both on the C57BL/6 background to investigate the impact bi-allelic TCR chain recombination has on T cell development, repertoire diversity, and autoimmunity. Lack of bi-allelic TCRα or TCRβ recombination reduced αβ thymocyte development efficiency, and the absence of bi-allelic TCRβ recombination promoted γδ T cell development. However, we observed no differences in the numbers of naïve and expanded antigen-specific T cells between TCRα^+/-β^+/- and wildtype mice, and TCR repertoire analysis revealed only subtle differences in Vβ gene usage. Finally, the absence of dual TCR T cells did not impact induced experimental autoimmune encephalomyelitis pathogenesis. Thus, despite more stringent allelic exclusion of TCRβ relative to TCRα, bi-allelic TCRβ expression can measurably impact thymocyte development and is necessary for maintaining normal αβ/γδ T cell proportions.

Barriers and alternatives to pediatric rheumatology referrals: survey of general pediatricians in the United States

BACKGROUND

Access to pediatric rheumatology (PR) care is limited, however the impact that limited access to PR has on pediatricians has not been examined. The goal of this study was to investigate barriers to PR referrals and resulting alternative referral patterns among primary pediatricians.

METHODS

A web-based survey was emailed to primary pediatricians practicing in Minnesota, North Dakota, and South Dakota in order to investigate access to PR care issues. Basic descriptive analysis was performed.

RESULTS

The response rate was 15 % (93/609). Twenty-nine percent (27/92) of respondents' clinics were at least two hours by car from a pediatric rheumatologist, and 9 % (8/92) were more than six hours away. Ninety-two percent (85/92) had referred a patient to PR at least once, but 89 % (83/93) had experienced a situation in which they considered a referral to PR but ultimately did not. Many had referred to other subspecialists instead: 29 % (24/83) to pediatric infectious disease, 20 % to adult rheumatology, and 12 % to pediatric orthopedics, while 34 % managed the patient themselves. Thirty-five percent (32/60) had referred to an adult rheumatologist, commonly due to decreased travel (44 %), while physician preference was never selected as a reason.

CONCLUSION

Pediatricians often refer children with possible rheumatic disease to specialists other than PR mainly due to long travel distances. Referral to adult rheumatologists occurs, but not based on pediatrician preference. These findings suggest that the PR workforce is inadequate to meet demand, at least in the Upper Midwest. Interventions are needed to improve access to PR care.

Fcγ receptor III and Fcγ receptor IV on macrophages drive autoimmune valvular carditis in mice

OBJECTIVE

Arthritis and valvular carditis coexist in several human rheumatic diseases, including systemic lupus erythematosus, rheumatic fever, and rheumatoid arthritis. T cell receptor-transgenic K/BxN mice develop spontaneous autoantibody-associated arthritis and valvular carditis. The common Fc receptor γ (FcRγ) signaling chain is required for carditis to develop in K/BxN mice. FcRγ pairs with numerous receptors in a variety of cells. The aim of this study was to identify the FcRγ-associated receptors and Fcγ receptor (FcγR)-expressing cells that mediate valvular carditis in this model.

METHODS

We bred K/BxN mice lacking the genes that encode activating Fcγ receptors (FcγRI, FcγRIII, and FcγRIV), and we assessed these mice for valvular carditis. We similarly evaluated complement component C3-deficient K/BxN mice. Immunohistochemistry, bone marrow transplantation, and macrophage depletion were used to define the key FcRγ-expressing cell type.

RESULTS

Genetic deficiency of only one of the activating Fcγ receptors did not prevent carditis, whereas deficiency of all 3 activating Fcγ receptors did. Further analysis demonstrated that FcγRIII and FcγRIV were the key drivers of valve inflammation; FcγRI was dispensable. C3 was not required. FcRγ expression by radioresistant cells was critical for valvular carditis to develop, and further analysis indicated that macrophages were the key candidate FcγR-expressing effectors of carditis.

CONCLUSION

FcγRIII and FcγRIV act redundantly to promote valvular carditis in K/BxN mice with systemic autoantibody-associated arthritis. Macrophage depletion reduced the severity of valve inflammation. These findings suggest that pathogenic autoantibodies engage Fcγ receptors on macrophages to drive valvular carditis. Our study provides new insight into the pathogenesis of cardiovascular inflammation in the setting of autoantibody-associated chronic inflammatory diseases.

Cutting edge: type 1 diabetes occurs despite robust anergy among endogenous insulin-specific CD4 T cells in NOD mice

Insulin-specific CD4(+) T cells are required for type 1 diabetes. How these cells are regulated and how tolerance breaks down are poorly understood because of a lack of reagents. Therefore, we used an enrichment method and tetramer reagents to track insulin-specific CD4(+) T cells in diabetes-susceptible NOD and resistant B6 mice expressing I-A(g7). Insulin-specific cells were detected in both strains, but they only became activated, produced IFN-γ, and infiltrated the pancreas in NOD mice. Unexpectedly, the majority of Ag-experienced cells in NOD mice displayed an anergic phenotype, but this population decreased with age as tolerance was lost. B6 mice expressing I-A(g7) were protected because insulin-specific cells did not become effector or anergic T cells but remained naive. These data suggest that NOD mice promote tolerance through anergy induction, but a small proportion of autoreactive T cells escape anergy to provoke type 1 diabetes.

The autoimmunity-associated gene PTPN22 potentiates toll-like receptor-driven, type 1 interferon-dependent immunity

Immune cells sense microbial products through Toll-like receptors (TLR), which trigger host defense responses including type 1 interferons (IFNs) secretion. A coding polymorphism in the protein tyrosine phosphatase nonreceptor type 22 (PTPN22) gene is a susceptibility allele for human autoimmune and infectious disease. We report that Ptpn22 selectively regulated type 1 IFN production after TLR engagement in myeloid cells. Ptpn22 promoted host antiviral responses and was critical for TLR agonist-induced, type 1 IFN-dependent suppression of inflammation in colitis and arthritis. PTPN22 directly associated with TNF receptor-associated factor 3 (TRAF3) and promotes TRAF3 lysine 63-linked ubiquitination. The disease-associated PTPN22W variant failed to promote TRAF3 ubiquitination, type 1 IFN upregulation, and type 1 IFN-dependent suppression of arthritis. The findings establish a candidate innate immune mechanism of action for a human autoimmunity "risk" gene in the regulation of host defense and inflammation.

Macrophage scavenger receptor 1 (Msr1, SR-A) influences B cell autoimmunity by regulating soluble autoantigen concentration

The class A macrophage scavenger receptor Msr1 (SR-A, CD204) has been reported to participate in the maintenance of immunological tolerance. We investigated the role of Msr1 in a mouse model of autoantibody-dependent arthritis. Genetic deficiency of Msr1 in K/BxN TCR transgenic mice decreased the incidence and severity of arthritis because of decreased autoantibody production. Despite normal initial activation of autoreactive CD4(+) T cells, potentially autoreactive B cells in Msr1(-/-) K/BxN mice retained a naive phenotype and did not expand. This was not due to an intrinsic B cell defect. Rather, we found that macrophages lacking Msr1 were inefficient at taking up the key autoantigen glucose-6-phosphate isomerase and that Msr1-deficient mice had elevated serum concentrations of glucose-6-phosphate isomerase. Arthritis developed normally when bone marrow from Msr1(-/-) K/BxN mice was transplanted into hosts whose macrophages did express Msr1. Thus, Msr1 can regulate the concentration of a soluble autoantigen. In this model, the absence of Msr1 led to higher levels of soluble autoantigen and protected mice from developing pathogenic autoantibodies, likely because of altered cognate interactions of autoreactive T and B cells with impaired differentiation of follicular Th cells.

Autoimmune retinopathy in a patient with autoimmune polyendocrine syndrome type I

PURPOSE

To present a case of autoimmune retinopathy resulting from a mutation in the autoimmune regulator (AIRE) gene.

DESIGN

Case study.

METHODS

Case review.

RESULTS

Mild improvement of goldmann visual field following treatment with systemic and local immunosuppression.

CONCLUSIONS

There are a limited number of cases linking autoimmune retinopathy with a mutation in the AIRE gene. Further research is needed to find more effective treatment and to prevent tissue damage.

Autoantibody-mediated arthritis in the absence of C3 and activating Fcγ receptors: C5 is activated by the coagulation cascade

Introduction

The effector functions of immunoglobulin G (IgG) are mediated by interaction of its Fc region with Fc receptors (FcγRs) and/or the complement system. The three main pathways of complement activation converge at C3. However, C3-independent pathways can activate C5 and other downstream complement components during IgG-initiated inflammatory responses. These C3-independent pathways of C5 activation are triggered by activating FcγRs in some systems or can be activated by factors of the coagulation cascade such as thrombin. Here we studied the interplay of C3, C5, and activating FcγRs in a model of spontaneous autoantibody-driven arthritis.

Methods

We utilized the K/BxN TCR transgenic mouse model of arthritis. We bred K/BxN mice bearing targeted or naturally-occurring mutations in one or more of the genes encoding complement components C3, C5, and FcRγ, the cytoplasmic signaling chain shared by the activating FcγRs. We measured arthritis development, the production of arthritogenic autoantibodies, T cell activation status and cytokine synthesis. In addition, we treated mice with anti-C5 monoclonal antibodies or with the thrombin inhibitor argatroban.

Results

We have previously shown that genetic deficiency of C5 protects K/BxN mice from the development of arthritis. We found here that C3-deficient K/BxN mice developed arthritis equivalent in severity to C3-sufficient animals. Arthritis also developed normally in K/BxN mice lacking both C3 and FcRγ, but could be ameliorated in these animals by treatment with anti-C5 monoclonal antibody or by treatment with argatroban. Production of arthritogenic autoantibodies, T cell activation, and T cell cytokine production were not affected by the absence of C3, C5, and/or FcRγ.

Conclusions

In K/BxN mice, C5-dependent autoantibody-driven arthritis can occur in the genetic absence of both complement C3 and activating FcγRs. Our findings suggest that in this setting, thrombin activates C5 to provoke arthritis.

Incomplete TCR-β allelic exclusion accelerates spontaneous autoimmune arthritis in K/BxN TCR transgenic mice

Allelic exclusion of antigen receptor loci is a fundamental mechanism of immunological self-tolerance. Incomplete allelic exclusion leads to dual T-cell receptor (TCR) expression and can allow developing autoreactive αβ T lymphocytes to escape clonal deletion. Because allelic exclusion at the TCR-β locus is more stringent than at the TCR-α locus, dual TCR-β expression has not been considered a likely contributor to autoimmunity. We show here that incomplete TCR-β allelic exclusion permits developing thymocytes bearing the autoreactive, transgene-encoded KRN TCR to be positively selected more efficiently, thereby accelerating the onset of spontaneous autoimmune arthritis. Our findings highlight dual TCR-β expression as a mechanism that can enhance the maturation of autoreactive pathogenic T cells and lead to more rapid development of autoimmune disease.

The neuropeptide neuromedin U promotes autoantibody-mediated arthritis

Introduction

Neuromedin U (NMU) is a neuropeptide with pro-inflammatory activity. The primary goal of this study was to determine if NMU promotes autoantibody-induced arthritis. Additional studies addressed the cellular source of NMU and sought to define the NMU receptor responsible for its pro-inflammatory effects.

Methods

Serum containing arthritogenic autoantibodies from K/BxN mice was used to induce arthritis in mice genetically lacking NMU. Parallel experiments examined whether NMU deficiency impacted the early mast-cell-dependent vascular leak response induced by these autoantibodies. Bone-marrow chimeric mice were generated to determine whether pro-inflammatory NMU is derived from hematopoietic cells or stromal cells. Mice lacking the known NMU receptors singly and in combination were used to determine susceptibility to serum-transferred arthritis and in vitro cellular responses to NMU.

Results

NMU-deficient mice developed less severe arthritis than control mice. Vascular leak was not affected by NMU deficiency. NMU expression by bone-marrow-derived cells mediated the pro-arthritogenic effect. Deficiency of all of the known NMU receptors, however, had no impact on arthritis severity and did not affect the ability of NMU to stimulate intracellular calcium flux.

Conclusions

NMU-deficient mice are protected from developing autoantibody-induced inflammatory arthritis. NMU derived from hematopoietic cells, not neurons, promotes the development of autoantibody-induced inflammatory arthritis. This effect is mediated by a receptor other than the currently known NMU receptors.

Arthritogenic self-reactive CD4+ T cells acquire an FR4hiCD73hi anergic state in the presence of Foxp3+ regulatory T cells

Rheumatoid arthritis develops in association with a defect in peripheral CD4(+) T cell homeostasis. T cell lymphopenia has also been shown to be a barrier to CD4(+) T cell clonal anergy induction. We therefore explored the relationship between clonal anergy induction and the avoidance of autoimmune arthritis by tracking the fate of glucose-6-phosphate isomerase (GPI)-reactive CD4(+) T cells in the setting of selective T cell lymphopenia. CD4(+) T cell recognition of self-GPI peptide/MHC class II complexes in normal murine hosts did not lead to arthritis and instead caused those T cells to develop a Folate receptor 4(hi)CD73(hi) anergic phenotype. In contrast, hosts selectively depleted of polyclonal Foxp3(+)CD4(+) regulatory T cells could not make GPI-specific CD4(+) T cells anergic and failed to control arthritis. This suggests that autoimmune arthritis develops in the setting of lymphopenia when Foxp3(+)CD4(+) regulatory T cells are insufficient to functionally inactivate all autoreactive CD4(+) T cells that encounter self-Ag.

Absence of β2 integrins impairs regulatory T cells and exacerbates CD4+ T cell-dependent autoimmune carditis

The immunopathogenic mechanisms mediating inflammation in multiorgan autoimmune diseases may vary between the different target tissues. We used the K/BxN TCR transgenic mouse model to investigate the contribution of CD4(+) T cells and β(2) integrins in the pathogenesis of autoimmune arthritis and endocarditis. Depletion of CD4(+) T cells following the onset of arthritis specifically prevented the development of cardiac valve inflammation. Genetic absence of β(2) integrins had no effect on the severity of arthritis and unexpectedly increased the extent of cardiovascular pathology. The exaggerated cardiac phenotype of the β(2) integrin-deficient K/BxN mice was accompanied by immune hyperactivation and was linked to a defect in regulatory T cells. These findings are consistent with a model in which the development of arthritis in K/BxN mice relies primarily on autoantibodies, whereas endocarditis depends on an additional contribution of effector T cells. Furthermore, strategies targeting β(2) integrins for the treatment of systemic autoimmune conditions need to consider not only the role of these molecules in leukocyte recruitment to sites of inflammation, but also their impact on the regulation of immunological tolerance.

Pericarditis as the presenting feature of adrenoleukodystrophy

X-linked adrenoleukodystrophy is characterized by elevated levels of very long chain fatty acids in the serum, brain, and adrenal glands that can lead to neurodevelopmental impairment and decreased adrenal function. We report here the case of a pediatric patient with pericarditis who was found to have adrenoleukodystrophy. More common causes of pericarditis (such as infectious, autoimmune, and metabolic) were excluded. On the basis of the examination finding of cutaneous hyperpigmentation, hypocortisolism was discovered. Further evaluation revealed elevated serum levels of very long chain fatty acids and a partial deletion of the ABCD1 gene, consistent with the diagnosis of X-linked adrenoleukodystrophy. Two of the index patient's brothers were subsequently found to have the same disease. Although pericarditis has been reported previously in association with autoimmune diseases that affect the adrenal glands, this is the first reported case (to our knowledge) of pericarditis in association with hypocortisolism from a nonautoimmune cause. Therefore, we suggest that hypocortisolism itself may lead to pericarditis in some patients.

Macrophage activation syndrome in patients with systemic juvenile idiopathic arthritis is associated with MUNC13-4 polymorphisms

OBJECTIVE

Systemic juvenile idiopathic arthritis (JIA) is associated with macrophage activation syndrome. Macrophage activation syndrome bears a close resemblance to familial hemophagocytic lymphohistiocytosis (HLH). The development of familial HLH has been recently associated with mutations in MUNC13-4. The purpose of this study was to assess for possible sequence alterations in MUNC13-4 in patients with systemic JIA/macrophage activation syndrome.

METHODS

The MUNC13-4 sequence was analyzed in 18 unrelated patients with systemic JIA/macrophage activation syndrome, using 32 primer pair sets designed to amplify the 32 exons and at least 100 basepairs of the adjacent intronic regions. DNA samples obtained from 73 unrelated patients with systemic JIA and no history of macrophage activation syndrome and 229 unrelated healthy individuals were used as controls.

RESULTS

The biallelic sequence variants in MUNC13-4 reported in familial HLH were present in 2 of the 18 patients with JIA/macrophage activation syndrome. Further analysis of the MUNC13-4 sequences revealed an identical combination of 12 single-nucleotide polymorphisms (SNPs) in 9 of the remaining 16 patients with systemic JIA/macrophage activation syndrome (56%). Additional analysis suggested that these 12 SNPs (154[-19] g>a, 261[+26] c>g, 388[+81] g>a, 388[+122] c>t, 570[-60] t>g, 888 G>C, 1389[+36] g>a, 1992[+5] g>a, 2447[+144] c>t, 2599 A>G, 2830[+37] c>g, 3198 A>G) were inherited as an extended haplotype. In several patients, in addition to the described haplotype, there were other SNPs in the second allele of MUNC13-4. Moreover, 1 patient had a complex mutation with 2 changes, 2542 A>C and 2943 G>C, in a cis configuration. The haplotype was present in only 27 (12%) of 229 healthy control subjects (chi(2) = 23.5) and in 6 (8.2%) of 73 patients with systemic JIA and no history of macrophage activation syndrome.

CONCLUSION

The data suggest an association between MUNC13-4 polymorphisms and macrophage activation syndrome in patients with systemic JIA.

Mutations of the hemophagocytic lymphohistiocytosis-associated gene UNC13D in a patient with systemic juvenile idiopathic arthritis

The clinical syndromes of hemophagocytic lymphohistiocytosis (HLH) and macrophage activation syndrome (MAS) are both characterized by dysregulated inflammation with prolonged fever, hepatosplenomegaly, coagulopathy, hematologic cytopenias, and evidence of hemophagocytosis in the bone marrow or liver. While HLH is either inherited or acquired, children with severe rheumatic diseases, most notably systemic juvenile idiopathic arthritis, are at risk for MAS. The phenotypic similarity between HLH and MAS raises the possibility that they share common pathogenetic mechanisms. Familial forms of HLH have been attributed to mutations in the genes encoding perforin (PRF1) and Munc13-4 (UNC13D), among others, and are characterized by defective cytotoxic lymphocyte function. While some patients with systemic JIA have decreased levels of perforin protein expression and natural killer (NK) cell function, mutations of HLH-associated genes in patients with systemic JIA have not been reported. We report the case of an 8-year-old girl with systemic JIA without MAS who was found to have compound heterozygous mutations of UNC13D and reduced NK cell cytotoxic function. This case broadens the range of clinical phenotypes attributable to UNC13D mutations and offers new insights into the etiology and pathogenesis of systemic JIA.

Clinical effects and safety of rituximab for treatment of refractory pediatric autoimmune diseases

OBJECTIVE

To evaluate the safety, tolerability, and clinical effects of rituximab, an anti-CD20 monoclonal antibody, in the treatment of severe pediatric autoimmune diseases.

STUDY DESIGN

We reviewed the records of 10 patients treated with rituximab for severe, refractory autoimmune diseases at a single tertiary care children's hospital. Adverse events as well as treatment effects were recorded.

RESULTS

All patients received 4 weekly doses of rituximab at 375 mg/m2 per dose. One patient died as the result of complications of her underlying systemic lupus erythematosus 7 weeks after rituximab therapy. Three patients had serious infections, all of which resolved with standard therapy. Rituximab led to transient or sustained improvement in clinical and laboratory parameters in nine subjects. At a median follow-up of 9 months, the median prednisone dose was reduced in the responders by 0.75 mg/kg per day (mean decrease of 63%), and four patients were able to discontinue corticosteroids entirely. With longer follow-up (median, 22 months), we found that 5 of 9 patients remained clinically stable after rituximab therapy, whereas 4 patients had recurrent or new features of their underlying autoimmune disorders requiring additional corticosteroids or other immunosuppressive medications.

CONCLUSIONS

Rituximab had an acceptable toxicity profile in this group of patients with severe, refractory autoimmune diseases, although there were three serious infections and one patient death. Rituximab appears to be beneficial for patients with refractory autoimmune diseases and may reduce corticosteroid exposure. Although rituximab therapy provided a durable clinical benefit for some patients in this population, other patients had reemergence of their underlying autoimmune disease.

Mast cells contribute to initiation of autoantibody-mediated arthritis via IL-1

Mast cells are immune sentinels that participate in the defense against bacteria and parasites. Resident within the joint, mast cells become activated in human rheumatoid arthritis and are implicated in the pathogenesis of experimental murine synovitis. However, their arthritogenic role remains undefined. Using a model of autoantibody-induced arthritis, we show that mast cells contribute to the initiation of inflammation within the joint by elaboration of IL-1. Mast cells become activated to produce this cytokine via the IgG immune complex receptor FcgammaRIII. Interestingly, mast cells become dispensable for the perpetuation of arthritis after delivery of IL-1, highlighting the contribution of this lineage to arthritis induction. These findings illuminate a mechanism by which mast cells can participate in the pathogenesis of autoimmune inflammatory arthritis and provide insights of potential relevance to human rheumatoid arthritis.