The class II peptide editor, H2-M, affects the development and repertoire of B-1 cells

Non-classical major histocompatibility complex class-II (MHCII) protein H2-M edits peptides bound to conventional MHCII (pMHCII) in favor of stable pMHCII complexes. Although the impact of H2-M deficiency on pMHCII expression and T cell activation is well-studied, information on how this protein affects the development and phenotypic profile of APCs is lacking. We found that the absence of H2-M in C57BL/6 (B6) mice, resulted in a loss of surface expression and peptide-cargo of MHCII molecules in B cells across lymphoid organs. Lower pMHCII expression reduced MHCII association with BCR, affecting the integrated BCR signaling. Importantly, in H2-M deficient B6 mice, compared to the wildtype mice, frequency and abundance of B-1 cells, but not conventional B-2 cells, was reduced in the spleen and peritoneum. This H2-M mediated effect on the B-1 cell population was only evident in the B6 background (I-Ab), but not in BALB/c (I-Ad/I-Ed), indicating an MHCII haplotype-dependent phenomenon. A decrease in B-1 cell number also was evident in immature B-1 cells, emphasizing that H2-M deficiency affects B-1 cell development. In H2-M KO mice compared to WT B6, B-1 cells display a significantly lower self-renewal capacity and a higher rate of apoptosis. Furthermore, H2-M deficiency alters the B-1 BCR repertoire, selecting for B-1 cells specific for highly abundant epitopes, but not for low-frequency epitopes. Collectively, these data identify the impact of H2-M/MHCII interaction as a regulator of BCR signaling that influences the selection, maturation, and maintenance of mature B-1 cell clones in the periphery.

Psoriatic arthritis in childhood: A commentary on the controversy

Approximately 5% of children with juvenile idiopathic arthritis (JIA) are diagnosed with the psoriatic form of the disease. In recent years, there has been substantial scholarship demonstrating both heterogeneity within the disease as well as similarities with other forms of JIA, culminating in a recent proposal for the categorization of JIA that excluded the psoriatic form altogether. The purpose of the review is to summarize the clinical, epidemiologic, and genetic features of psoriatic JIA (PsJIA), comparing it with other categories of JIA including spondyloarthritis. We conclude that there are sufficient unique clinical and genetic features within PsJIA as well as similarities with its adult counterpart that warrant including it within the JIA paradigm.

HLA associations in inflammatory arthritis: emerging mechanisms and clinical implications

Our understanding of the mechanisms underlying HLA associations with inflammatory arthritis continues to evolve. Disease associations have been refined, and interactions of HLA genotype with other genes and environmental risk factors in determining disease risk have been identified. This Review provides basic information on the genetics and molecular function of HLA molecules, as well as general features of HLA associations with disease. Evidence is discussed regarding the various peptide-dependent and peptide-independent mechanisms by which HLA alleles might contribute to the pathogenesis of three types of inflammatory arthritis: rheumatoid arthritis, spondyloarthritis and systemic juvenile idiopathic arthritis. Also discussed are HLA allelic associations that shed light on the genetic heterogeneity of inflammatory arthritides and on the relationships between adult and paediatric forms of arthritis. Clinical implications range from improved diagnosis and outcome prediction to the possibility of using HLA associations in developing personalized strategies for the treatment and prevention of these diseases.

Combined Assay for Detecting Autoantibodies to Nucleic Acids and Apolipoprotein H in Patients with Systemic Lupus Erythematosus

The complicated clinical picture and biomolecular pattern of human autoimmune diseases (ADs) make knowledge on their etiology still fragmentary. The diagnostic approaches for ADs require improvement both for clinical and research effort to progress. Synthetic biomolecular antigens find growing applications for diagnosis and investigation of ADs. The main goal of this work is to detect interaction between synthetic antigens and autoantibodies in systemic lupus erythematosus within a combined, high-throughput assay. A panel of synthetic antigens has been prepared from DNA, RNA, locked nucleic acids and apolipoprotein H. The binding of synthetic antigens to autoantibodies has been confirmed in sera samples from those with active systemic lupus erythematosus (SLE) by indirect enzyme linked immunosorbent assay. Our study provides an efficient methodology for combined autoantibody profiling in SLE.

Diacylglycerol Kinase ζ Regulates Macrophage Responses in Juvenile Arthritis and Cytokine Storm Syndrome Mouse Models

Dysregulation of monocyte and macrophage responses are often observed in children with systemic juvenile idiopathic arthritis (sJIA) and cytokine storm syndrome (CSS), a potentially fatal complication of chronic rheumatic diseases. Both conditions are associated with activation of TLR signaling in monocyte and macrophage lineage cells, leading to overwhelming inflammatory responses. Despite the importance of TLR engagement in activating proinflammatory macrophages, relatively little is known about activation of intrinsic negative regulatory pathways to attenuate excessive inflammatory responses. In this study, we demonstrate that loss of diacylglycerol (DAG) kinase (Dgk) ζ, an enzyme which converts DAG into phosphatidic acid, limits inflammatory cytokine production in an arthritic mouse model dependent on TLR2 signaling and in a CSS mouse model dependent on TLR9 signaling. In vitro, Dgkζ deficiency results in reduced production of TNF-α, IL-6, and IL-1β and in limited M1 macrophage polarization. Mechanistically, Dgkζ deficiency decreases STAT1 and STAT3 phosphorylation. Moreover, Dgkζ levels are increased in macrophages derived from mice with CSS or exposed to plasma from sJIA patients with active disease. Our data suggest that Dgkζ induction in arthritic conditions perpetuates systemic inflammatory responses mediated by macrophages and highlight a potential role of Dgkζ-DAG/phosphatidic acid axis as a modulator of inflammatory cytokine production in sJIA and CSS.

Emergent high fatality lung disease in systemic juvenile arthritis

OBJECTIVE

To investigate the characteristics and risk factors of a novel parenchymal lung disease (LD), increasingly detected in systemic juvenile idiopathic arthritis (sJIA).

METHODS

In a multicentre retrospective study, 61 cases were investigated using physician-reported clinical information and centralised analyses of radiological, pathological and genetic data.

RESULTS

LD was associated with distinctive features, including acute erythematous clubbing and a high frequency of anaphylactic reactions to the interleukin (IL)-6 inhibitor, tocilizumab. Serum ferritin elevation and/or significant lymphopaenia preceded LD detection. The most prevalent chest CT pattern was septal thickening, involving the periphery of multiple lobes ± ground-glass opacities. The predominant pathology (23 of 36) was pulmonary alveolar proteinosis and/or endogenous lipoid pneumonia (PAP/ELP), with atypical features including regional involvement and concomitant vascular changes. Apparent severe delayed drug hypersensitivity occurred in some cases. The 5-year survival was 42%. Whole exome sequencing (20 of 61) did not identify a novel monogenic defect or likely causal PAP-related or macrophage activation syndrome (MAS)-related mutations. Trisomy 21 and young sJIA onset increased LD risk. Exposure to IL-1 and IL-6 inhibitors (46 of 61) was associated with multiple LD features. By several indicators, severity of sJIA was comparable in drug-exposed subjects and published sJIA cohorts. MAS at sJIA onset was increased in the drug-exposed, but was not associated with LD features.

CONCLUSIONS

A rare, life-threatening lung disease in sJIA is defined by a constellation of unusual clinical characteristics. The pathology, a PAP/ELP variant, suggests macrophage dysfunction. Inhibitor exposure may promote LD, independent of sJIA severity, in a small subset of treated patients. Treatment/prevention strategies are needed.

Systemic Juvenile Idiopathic Arthritis-Associated Lung Disease: Characterization and Risk Factors

OBJECTIVE

Systemic juvenile idiopathic arthritis (JIA) is associated with a recently recognized, albeit poorly defined and characterized, lung disease (LD). The objective of this study was to describe the clinical characteristics, risk factors, and histopathologic and immunologic features of this novel inflammatory LD associated with systemic JIA (designated SJIA-LD).

METHODS

Clinical data collected since 2010 were abstracted from the medical records of patients with systemic JIA from the Cincinnati Children's Hospital Medical Center. Epidemiologic, cellular, biochemical, genomic, and transcriptional profiling analyses were performed.

RESULTS

Eighteen patients with SJIA-LD were identified. Radiographic findings included diffuse ground-glass opacities, subpleural reticulation, interlobular septal thickening, and lymphadenopathy. Pathologic findings included patchy, but extensive, lymphoplasmacytic infiltrates and mixed features of pulmonary alveolar proteinosis (PAP) and endogenous lipoid pneumonia. Compared to systemic JIA patients without LD, those with SJIA-LD were younger at the diagnosis of systemic JIA (odds ratio [OR] 6.5, P = 0.007), more often had prior episodes of macrophage activation syndrome (MAS) (OR 14.5, P < 0.001), had a greater frequency of adverse reactions to biologic therapy (OR 13.6, P < 0.001), and had higher serum levels of interleukin-18 (IL-18) (median 27,612 pg/ml versus 5,413 pg/ml; P = 0.047). Patients with SJIA-LD lacked genetic, serologic, or functional evidence of granulocyte-macrophage colony-stimulating factor pathway dysfunction, a feature that is typical of familial or autoimmune PAP. Moreover, bronchoalveolar lavage (BAL) fluid from patients with SJIA-LD rarely demonstrated proteinaceous material and had less lipid-laden macrophages than that seen in patients with primary PAP (mean 10.5% in patients with SJIA-LD versus 66.1% in patients with primary PAP; P < 0.001). BAL fluid from patients with SJIA-LD contained elevated levels of IL-18 and the interferon-γ-induced chemokines CXCL9 and CXCL10. Transcriptional profiling of the lung tissue from patients with SJIA-LD identified up-regulated type II interferon and T cell activation networks. This signature was also present in SJIA-LD human lung tissue sections that lacked substantial histopathologic findings, suggesting that this activation signature may precede and drive the lung pathology in SJIA-LD.

CONCLUSION

Pulmonary disease is increasingly detected in children with systemic JIA, particularly in association with MAS. This entity has distinct clinical and immunologic features and represents an uncharacterized inflammatory LD.

Citrullinated Peptide Epitope Targets Therapeutic Nanoparticles to Human Neutrophils

Multiple drugs have been proposed for reducing harsh symptoms of human rheumatic diseases. However, a targeted therapy with mild to no side effects is still missing. In this study, we have prepared and tested a series of therapeutic nanoparticles for specific targeting of human neutrophils associated with rheumatoid arthritis. In doing this, a series of citrullinated peptide epitopes derived from human proteins, fibrinogen, vimentin, and histone 3, were screened with regard to specific recognition of neutrophils. The most potent epitope proved to be a mutated fragment of an alpha chain in human fibrinogen. Next, a straightforward synthetic strategy was developed for nanoparticles decorated with this citrullinated peptide epitope and an antisense oligonucleotide targeting disease associated microRNA miR-125b-5p. Our study shows that the nanoparticles specifically recognize neutrophils and knock down miR-125b-5p, with no apparent toxicity to human cells. In contrast to organic dendrimers, chitosan-hyaluronic acid formulations do not activate human innate immune response. Our data proves that the strategy we report herein is effective in developing peptide epitopes for decorating delivery vehicles bearing biological drugs, targeted to a specific cell type.

Human Intestinal Enteroids Model MHC-II in the Gut Epithelium

The role of intestinal epithelial cells (IECs) in mucosal tolerance and immunity remains poorly understood. We present a method for inducing MHC class II (MHC-II) in human enteroids, "mini-guts" derived from small intestinal crypt stem cells, and show that the intracellular MHC-II peptide-pathway is intact and functional in IECs. Our approach enables human enteroids to be used for novel in vitro studies into IEC MHC-II regulation and function during health and disease.

The class II peptide editor, H2-M, affects the development and function of B-1 cells

B-1 cells are known for their innate, polyreactive BCR repertoire, and proficiency at polarizing T cells towards inflammatory effector T cells, a critical component in host defense and autoimmunity. B-1 cells are antigen presenting cells (APCs) and express MHCII proteins to bind and display self and foreign peptides to CD4 T cells. H2-M edits peptide-MHCII complexes to ensure display of stably bound peptides by APCs. Absence of H2-M has most widely been studied for its impact on T cell activation, but knowledge of how this protein affects the development and function of APCs is lacking. We found that absence of H2-M down-regulated the surface expression and altered the distribution of MHCII molecules in B cells across lymphoid organs. Importantly, in H2-M KO mice, compared to the wild-type C57BL/6 (B6) mice, the frequency and abundance of B-1 cells, but not conventional B-2 cells was affected. Interestingly, the H2-M mediated effect on B-1 cell population was only evident in I-Ab expressing B6, not in Balb/c (I-Ad/I-Ed), indicating an MHCII haplotype dependent effect. Decrease in B-1 cell number was evident in both immature and mature B-1 cells, further indicating an H2-M mediated developmental defect of B-1 cells. In H2-M KO mice, B-1 cells display a significantly lower self-renewal capacity and higher rate of apoptosis compared to WT B6. Despite a lower total B-1 cell number, the frequency of B-1 cells specific for predominant self-antigens (like – phosphatidylcholine) is increased in H2-M KO mice, indicating skewing of B-1 BCR repertoire in absence of H2-M. Collectively, these data identify a novel impact of H2-M/MHCII interaction that regulates the development of B-1 cells and influences the selection of mature B-1 cell clones in the periphery.

Tmem178 negatively regulates store-operated calcium entry in myeloid cells via association with STIM1

Store-operated calcium entry (SOCE) modulates cytosolic calcium in multiple cells. Endoplasmic reticulum (ER)-localized STIM1 and plasma membrane (PM)-localized ORAI1 are two main components of SOCE. STIM1:ORAI1 association requires STIM1 oligomerization, its re-distribution to ER-PM junctions, and puncta formation. However, little is known about the negative regulation of these steps to prevent calcium overload. Here, we identified Tmem178 as a negative modulator of STIM1 puncta formation in myeloid cells. Using site-directed mutagenesis, co-immunoprecipitation assays and FRET imaging, we determined that Tmem178:STIM1 association occurs via their transmembrane motifs. Mutants that increase Tmem178:STIM1 association reduce STIM1 puncta formation, SOCE activation, impair inflammatory cytokine production in macrophages and osteoclastogenesis. Mutants that reduce Tmem178:STIM1 association reverse these effects. Furthermore, exposure to plasma from arthritic patients decreases Tmem178 expression, enhances SOCE activation and cytoplasmic calcium. In conclusion, Tmem178 modulates the rate-limiting step of STIM1 puncta formation and therefore controls SOCE in inflammatory conditions.

Epitope Selection for HLA-DQ2 Presentation: Implications for Celiac Disease and Viral Defense

We have reported that the major histocompatibility molecule HLA-DQ2 (DQA1*05:01/DQB1*02:01) (DQ2) is relatively resistant to HLA-DM (DM), a peptide exchange catalyst for MHC class II. In this study, we analyzed the role of DQ2/DM interaction in the generation of DQ2-restricted gliadin epitopes, relevant to celiac disease, or DQ2-restricted viral epitopes, relevant to host defense. We used paired human APC, differing in DM expression (DM^null versus DM^high) or differing by expression of wild-type DQ2, versus a DM-susceptible, DQ2 point mutant DQ2α+53G. The APC pairs were compared for their ability to stimulate human CD4⁺ T cell clones. Despite higher DQ2 levels, DM^high APC attenuated T cell responses compared with DM^null APC after intracellular generation of four tested gliadin epitopes. DM^high APC expressing the DQ2α+53G mutant further suppressed these gliadin-mediated responses. The gliadin epitopes were found to have moderate affinity for DQ2, and even lower affinity for the DQ2 mutant, consistent with DM suppression of their presentation. In contrast, DM^high APC significantly promoted the presentation of DQ2-restricted epitopes derived intracellularly from inactivated HSV type 2, influenza hemagglutinin, and human papillomavirus E7 protein. When extracellular peptide epitopes were used as Ag, the DQ2 surface levels and peptide affinity were the major regulators of T cell responses. The differential effect of DM on stimulation of the two groups of T cell clones implies differences in DQ2 presentation pathways associated with nonpathogen- and pathogen-derived Ags in vivo.

Epithelial MHC Class II Expression and Its Role in Antigen Presentation in the Gastrointestinal and Respiratory Tracts

As the primary barrier between an organism and its environment, epithelial cells are well-positioned to regulate tolerance while preserving immunity against pathogens. Class II major histocompatibility complex molecules (MHC class II) are highly expressed on the surface of epithelial cells (ECs) in both the lung and intestine, although the functional consequences of this expression are not fully understood. Here, we summarize current information regarding the interactions that regulate the expression of EC MHC class II in health and disease. We then evaluate the potential role of EC as non-professional antigen presenting cells. Finally, we explore future areas of study and the potential contribution of epithelial surfaces to gut-lung crosstalk.

IL1RN Variation Influences Both Disease Susceptibility and Response to Recombinant Human Interleukin-1 Receptor Antagonist Therapy in Systemic Juvenile Idiopathic Arthritis

OBJECTIVE

To determine whether systemic juvenile idiopathic arthritis (JIA) susceptibility loci that were identified by candidate gene studies demonstrate association with systemic JIA in the largest study population assembled to date.

METHODS

Single-nucleotide polymorphisms (SNPs) from 11 previously reported systemic JIA risk loci were examined for association in 9 populations, including 770 patients with systemic JIA and 6,947 controls. The effect of systemic JIA-associated SNPs on gene expression was evaluated in silico in paired whole genome and RNA sequencing data from the lymphoblastoid cell lines (LCLs) of 373 European subjects from the 1000 Genomes Project. Responses of systemic JIA-associated SNPs to anakinra treatment were evaluated in 38 US patients for whom treatment response data were available.

RESULTS

We found no association between the previously reported 26 SNPs and systemic JIA. Expanded analysis of the regions containing the 26 SNPs revealed only 1 significant association: the promoter region of IL1RN (P < 1 × 10-4 ). Systemic JIA-associated SNPs correlated with IL1RN expression in LCLs, with an inverse correlation between systemic JIA risk and IL1RN expression. The presence of homozygous IL1RN high expression alleles correlated strongly with a lack of response to anakinra therapy (odds ratio 28.7 [95% confidence interval 3.2-255.8]).

CONCLUSION

In our study, IL1RN was the only candidate locus associated with systemic JIA. The implicated SNPs are among the strongest known determinants of IL1RN and interleukin-1 receptor antagonist levels, linking low expression with increased systemic JIA risk. Homozygous high expression alleles predicted nonresponsiveness to anakinra therapy, making them ideal candidate biomarkers to guide systemic JIA treatment. This study is an important first step toward the personalized treatment of systemic JIA.

Interleukin-1 in monocyte activation phenotypes in systemic juvenile idiopathic arthritis: Observations from a clinical trial of rilonacept, an interleukin-1 inhibitor

Systemic juvenile idiopathic arthritis (sJIA) is a childhood rheumatic disease of unknown origin. Dysregulated innate immunity is implicated in disease pathology. We investigated if IL-1 inhibition affects circulating cytokines and monocyte gene expression. CD14+ monocytes from patients in the RAPPORT trial were analyzed by RT-PCR for expression of IL1B and transcription factors associated with monocyte activation. Serum IL-1ra decreased with treatment, and IL-18BP transiently increased. Serum levels of IL-1β, IL-6, IL-10 and IL-18 were unchanged. IRF5 and STAT6 were decreased, and PPARG was increased, independent of clinical response, and may represent a skew toward a PPARG-driven M2-like phenotype. IL1B expression was decreased in early clinical responders. A transient increase in STAT1, and a decrease in SOCS1 preceded the reduction in IL1B in early clinical responders. Changes in IL1B/STAT1/SOCS1 could be associated with crosstalk between IL-1 and IFN pathways in sJIA. These transcriptional changes might be useful as drug response biomarkers.

Juvenile Psoriatic Arthritis: A Report from the GRAPPA 2017 Annual Meeting

Juvenile psoriatic arthritis (JPsA), a subtype of juvenile idiopathic arthritis (JIA), constitutes 5% of JIA. The literature is inconsistent regarding features of JPsA, and physicians debate whether it is a distinct entity within JIA. A biphasic age of onset distribution has been noted. Early-onset disease is characterized by female predominance, small joint involvement, dactylitis, and positive antinuclear antibodies. Late-onset JPsA resembles adult-onset psoriatic arthritis (PsA), with male predominance, psoriasis, enthesitis, and axial disease. Recent studies report improved outcomes, likely due to the widespread use of traditional and biologic disease-modifying antirheumatic drugs. Conflicting HLA associations have been reported in JPsA, but notably both HLA class I and II allele associations are suggested. Similar to PsA cohorts, subjects with JPsA have a lower frequency of a protective interleukin 23R allele than controls or other JIA subtypes. Data in the Childhood Arthritis and Rheumatology Research Alliance (CARRA) patient registry suggest the aggressive characteristics of JPsA: 24.6% of children have joint damage 4.6 years after symptom onset. Pediatric and adult PsA classification criteria define different JPsA cohorts within the registry and support a previous suggestion that the International League of Associations for Rheumatology criteria for JPsA may be overly stringent. Increased collaboration between pediatric and adult physicians and comparative research on these clinically related conditions are warranted.

A myeloid population potentially corresponding to myeloid monocytic suppressor cells (MoMDSCs) is increased in the blood of Rheumatoid Arthritis patients and associated with osteoclastogenesis

The development of erosive arthritis and joint damage are common and severe complications of rheumatoid arthritis (RA). Erosions are caused by excessive activity of osteoclasts (OCs), the only known bone resorbing cells. OCs are myeloid lineage cells and can be generated in vitro from CD14+ circulating myeloid cells, using RANKL and M-CSF. To characterize circulating myeloid lineage cells in RA, we performed mass cytometry (CyTOF) analysis of blood from 11 RA patients and 10 age and gender-matched healthy controls. Using CITRUS analysis, we found a myeloid cell cluster that is significantly elevated in RA patients compared to healthy subjects. The phenotype of this cluster is CD11b+, CD14+, CD16−, HLA-DR-/lo, CCR2hi, RANKhi, and phosphorylated (p)STAT3hi. The surface phenotype of this cluster is associated with monocytic myeloid derived suppressor cells (MoMDSCs). Analysis by conventional flow of a separate group of 14 RA patients showed that frequency of these myeloid cells correlates with number of blood osteoclasts precursors (OCP) based on the in vitro assay. Baseline level of pSrc and pJNK in these cells also correlated with OCP numbers. Both of these molecules are involved in downstream signaling cascades involved in osteoclastogenesis and osteoclast survival. We also found that intermediate (CD14++CD16+) monocytes are elevated in RA, as previously described, but these cells did not show a positive correlation with OCP numbers. These results indicate that a group of myeloid cells, potentially corresponding to MoMDSCs, are elevated in the blood of RA patients. Their phenotype (high RANK, phosphorylated Src, phosphorylated JNK) and frequency indicate that they may be involved in osteoclastogenesis, as described in mouse models.

Single-walled carbon nanotubes target neutrophils and Ly-6Chi monocytes and localize to joints in murine models of arthritis

Rheumatoid arthritis (RA) is a chronic autoimmune disease that often leads to joint damage. The etiology of RA remains unclear, but new insights and therapeutic strategies have been facilitated by murine models. In the K/BxN serum transfer (STA) model, arthritis is triggered by autoantibodies against glucose-6-phosphate isomerase. The SKG model has a ZAP70 point mutation that reduces TCR signaling. After zymosan exposure, SKG mice develop arthritis, mediated by autoreactive Th17 cells. Joint inflammation in these models shares many features with RA, including leukocyte invasion, synovitis, and bone resorption. Neutrophils and Ly-6Chi monocytes are known to play critical roles in these models.1–4 Here, we investigated single-walled carbon nanotubes (SWNT) as candidate drug carriers to specifically target pathogenic cells in arthritic joints. Using FACS analysis, we found that, 2h and 4h after IV administration of SWNT, nearly 80% Ly-6Chi monocytes in blood had taken up SWNT in STA and SKG model, respectively. Near-infrared (NIR) photoluminescence whole-animal imaging of the STA model showed that SWNT were first detected in arthritic joints 3h post injection (p.i.) and reached a maximal level 24h p.i., In contrast, in non-arthritic mice, SWNT detected in joints remained low 24h p.i., suggesting SWNT can specifically target cells homing to or present in arthritic joints. In SKG mice, 2d p.i., SWNT were found in Ly-6Chi monocyte and in neutrophils in bone marrow and liver, but not in blood and spleen. FACS analysis indicated specific uptake of SWNT labelled with Cy5.5 in monocytes and neutrophils in human blood. We conclude that SWNT is a potential carrier to target drugs to pathogenic neutrophils and monocytes in arthritic joints.

Brief Report: The Genetic Profile of Rheumatoid Factor-Positive Polyarticular Juvenile Idiopathic Arthritis Resembles That of Adult Rheumatoid Arthritis

Objective

Juvenile idiopathic arthritis (JIA) comprises 7 heterogeneous categories of chronic childhood arthritides. Approximately 5% of children with JIA have rheumatoid factor (RF)–positive arthritis, which phenotypically resembles adult rheumatoid arthritis (RA). Our objective was to compare and contrast the genetics of RF‐positive polyarticular JIA with those of RA and selected other JIA categories, to more fully understand the pathophysiologic relationships of inflammatory arthropathies.

Methods

Patients with RF‐positive polyarticular JIA (n = 340) and controls (n = 14,412) were genotyped using the Immunochip array. Single‐nucleotide polymorphisms were tested for association using a logistic regression model adjusting for admixture proportions. We calculated weighted genetic risk scores (wGRS) of reported RA and JIA risk loci, and we compared the ability of these wGRS to predict RF‐positive polyarticular JIA.

Results

As expected, the HLA region was strongly associated with RF‐positive polyarticular JIA (P = 5.51 × 10⁻³¹). Nineteen of 44 RA risk loci and 6 of 27 oligoarticular/RF‐negative polyarticular JIA risk loci were associated with RF‐positive polyarticular JIA (P < 0.05). The RA wGRS predicted RF‐positive polyarticular JIA (area under the curve [AUC] 0.71) better than did the oligoarticular/RF‐negative polyarticular JIA wGRS (AUC 0.59). The genetic profile of patients with RF‐positive polyarticular JIA was more similar to that of RA patients with age at onset 16–29 years than to that of RA patients with age at onset ≥70 years.

Conclusion

RF‐positive polyarticular JIA is genetically more similar to adult RA than to the most common JIA categories and thus appears to be a childhood‐onset presentation of autoantibody‐positive RA. These findings suggest common disease mechanisms, which could lead to novel therapeutic targets and shared treatment strategies.

Detection of autoimmune antibodies in localized scleroderma by synthetic oligonucleotide antigens

In this study, we developed a series of synthetic oligonucleotides that allowed us to investigate the details on the antigen recognition by autoimmune antibodies in localized scleroderma subjects. Besides dramatically improved analytical specificity of the assay, our data suggests a potential linking for antibodies to DNA to the biological status of disease state in localized scleroderma. Moreover, introducing chemical modifications into short synthetic deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) molecules completely changed the binding titers of corresponding antibodies and their clinical relevance. The strongest observed effect was registered for the localized scleroderma skin damage index (LoSDI) on the IgG antibodies to TC dinucleotide-rich double-stranded antigen (p < 0.001). In addition to providing valuable tools for diagnosis of clinically relevant biomarkers, we believe that this work opens up new opportunities for research on antibodies to nucleic acids in localized scleroderma and other autoimmune diseases.

Autoantibody Profiling in Lupus Patients using Synthetic Nucleic Acids

Autoantibodies to nuclear components of cells (antinuclear antibodies, ANA), including DNA (a-DNA), are widely used in the diagnosis and subtyping of certain autoimmune diseases, including systemic lupus erythematosus (SLE). Despite clinical use over decades, precise, reproducible measurement of a-DNA titers remains difficult, likely due to the substantial sequence and length heterogeneity of DNA purified from natural sources. We designed and tested a panel of synthetic nucleic acid molecules composed of native deoxyribonucleotide units to measure a-DNA. ELISA assays using these antigens show specificity and reproducibility. Applying the ELISA tests to serological studies of pediatric and adult SLE, we identified novel clinical correlations. We also observed preferential recognition of a specific synthetic antigen by antibodies in SLE sera. We determined the probable basis for this finding using computational analyses, providing valuable structural information for future development of DNA antigens. Synthetic nucleic acid molecules offer the opportunity to standardize assays and to dissect antibody-antigen interactions.

Adiposity in Juvenile Psoriatic Arthritis

OBJECTIVE

Adult patients with psoriatic arthritis are at increased risk for obesity and metabolic syndrome, but data regarding adiposity in children with juvenile psoriatic arthritis (JPsA) are limited. Our study assessed adiposity in children with JPsA in the Childhood Arthritis and Rheumatology Research Alliance (CARRA) registry.

METHODS

Patients with JPsA in the CARRA registry were divided into nonoverweight and overweight groups using recommendations from the US Centers for Disease Control, and differences in demographic and clinical characteristics between groups at baseline and after 1-year followup were assessed using chi-square test, Fisher's exact test, T test, or Mann-Whitney U test, as appropriate. The prevalence of overweight status in the JPsA registry patients was compared to rheumatoid factor-positive and -negative polyarticular juvenile idiopathic arthritis (RF+polyJIA; RF-polyJIA) registry cohorts and the US pediatric population, using a chi-square goodness-of-fit test.

RESULTS

Overweight children represented 36.3% of this JPsA cohort (n = 320). Compared to nonoverweight children, they were significantly older at symptom onset and rheumatologist's first assessment, and scored significantly worse on patient/physician outcome measures. At 1-year followup, changes in body mass index were not associated with changes in clinical features or outcome measures. The prevalence of overweight and obesity in patients with JPsA was significantly higher than in RF+polyJIA patients, RF-polyJIA patients, and the US pediatric population.

CONCLUSION

In this registry, almost 1 in 5 patients with JPsA were obese and more than one-third were overweight. This is significantly more than expected compared to the US pediatric population, and appropriate longterm followup of this JPsA subgroup is warranted.