The unique interplay between antinuclear antibodies and nuclear molecules in the pathogenesis of SLE.

Systemic lupus erythematosus (SLE) is a prototypic autoimmune disease that primarily affects young women and causes a wide range of inflammatory manifestations. The hallmark of SLE is the production of antibodies to components of the cell nucleus (antinuclear antibodies or ANAs). These antibodies can bind to DNA, RNA and protein complexes with nucleic acids. Among ANAs, antibodies to DNA (anti-DNA) are markers for classification and disease activity, waxing and waning in many patients. In the blood, anti-DNA antibodies can bind DNA to form immune complexes with two distinct roles in pathogenesis: renal deposition to provoke nephritis and stimulation of cytokine production following uptake into innate immune cells and interaction with internal nucleic acid sensors. These sensors are part of an internal host defense system in the cell cytoplasm that can respond to DNA from infecting organisms; during cell stress, DNA from nuclear and mitochondrial sources can also trigger these sensors. The formation of immune complexes requires a source of extracellular DNA in an immunologically accessible form. As shown in in vivo and in vitro systems, extracellular DNA can emerge from dead and dying cells in both a free and particulate form. Neutrophils undergoing the process of NETosis can release DNA in mesh-like structures called NETs (neutrophil extracellular traps). In SLE, therefore, the combination of ANAs and immunologically active DNA can create new structures which can promote inflammation throughout the body as well as drive organ inflammation and damage.

The Binding Properties of Antibodies to Z-DNA in the Sera of Normal Healthy Subjects.

Antibodies to DNA are a diverse set of antibodies that bind sites on DNA, a polymeric macromolecule that displays various conformations. In a previous study, we showed that sera of normal healthy subjects (NHS) contain IgG antibodies to Z-DNA, a left-handed helix with a zig-zig backbone. Recent studies have demonstrated the presence of Z-DNA in bacterial biofilms, suggesting a source of this conformation to induce responses. To characterize further antibodies to Z-DNA, we used an ELISA assay with brominated poly(dGdC) as a source of Z-DNA and determined the isotype of these antibodies and their binding properties. Results of these studies indicate that NHS sera contain IgM and IgA as well as IgG anti-Z-DNA antibodies. As shown by the effects of ionic strength in association and dissociation assays, the anti-Z-DNA antibodies bind primarily by electrostatic interactions; this type of binding differs from that of induced anti-Z-DNA antibodies from immunized animals which bind by non-ionic interactions. Furthermore, urea caused dissociation of NHS anti-Z-DNA at molar concentrations much lower than those for the induced antibodies. These studies also showed IgA anti-Z-DNA antibodies in fecal water. Together, these studies demonstrate that antibodies to Z-DNA occur commonly in normal immunity and may arise as a response to Z-DNA of bacterial origin.

DNA corona on nanoparticles leads to an enhanced immunostimulatory effect with implications for autoimmune diseases.

Autoimmune and inflammatory diseases are highly complex, limiting treatment and the development of new therapies. Recent work has shown that cell-free DNA bound to biological microparticles is linked to systemic lupus erythematosus, a prototypic autoimmune disease. However, the heterogeneity and technical challenges associated with the study of biological particles have hindered a mechanistic understanding of their role. Our goal was to develop a well-controlled DNA-particle model system to understand how DNA-particle complexes affect cells. We first characterized the adsorption of DNA on the surface of polystyrene nanoparticles (200 nm and 2 µm) using transmission electron microscopy, dynamic light scattering, and colorimetric DNA concentration assays. We found that DNA adsorbed on the surface of nanoparticles was resistant to degradation by DNase 1. Macrophage cells incubated with the DNA-nanoparticle complexes had increased production of pro-inflammatory cytokines tumor necrosis factor alpha (TNF-α) and interleukin 6 (IL-6). We probed two intracellular DNA sensing pathways, toll-like receptor 9 (TLR9) and cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING), to determine how cells sense the DNA-nanoparticle complexes. We found that the cGAS-STING pathway is the primary route for the interaction between DNA-nanoparticles and macrophages. These studies provide a molecular and cellular-level understanding of DNA-nanoparticle-macrophage interactions. In addition, this work provides the mechanistic information necessary for future in vivo experiments to elucidate the role of DNA-particle interactions in autoimmune diseases, providing a unique experimental framework to develop novel therapeutic approaches.

Evaluation of Type 2 SLE symptoms in patients with a range of lupus nephritis activity.

BACKGROUND: Type 2 systemic lupus erythematosus (SLE) symptoms, including fatigue, fibromyalgia, and brain fog, contribute to poor health-related quality of life (HRQoL) in patients with lupus. To test the hypothesis that Type 1 (classical inflammatory lupus) activity is associated with Type 2 SLE activity, we characterized the features of Type 2 SLE in patients with a range of lupus nephritis (LN) activity. METHODS: This was a cross-sectional study of SLE patients [American College of Rheumatology (ACR) 1997 or Systemic Lupus International Collaborating Clinics (SLICC) 2012 classification criteria] from June 2018 to March 2020. Patients completed the Systemic Lupus Activity Questionnaire (SLAQ) and the Polysymptomatic Distress Scale. Patients were divided into groups based on their renal status. Active nephritis was defined using the Systemic Lupus Erythematosus Disease Activity Index (SLEDAI) lupus nephritis parameter. Differences across groups were analyzed by Fisher's exact test and ANOVA. RESULTS: In this cohort of 244 patients (93% female, mean age 43 years, 58% Black), 10% had active nephritis, 35% had historical nephritis, and 55% never had nephritis (non-nephritis). Active nephritis and non-nephritis patients had a similar burden of Type 2 SLE symptoms, despite a difference in Type 1 SLE activity. Patients with active nephritis had higher Type 2 PGA (Physician Global Assessment) scores and reported more Type 2 SLE symptoms than inactive nephritis patients. Patients with inactive nephritis had the lowest Type 2 SLE activity. CONCLUSIONS: While Type 2 SLE symptoms are common in SLE, our findings suggest that patients with active nephritis experience significant Type 2 SLE symptoms that may be ameliorated as nephritis improves. We also observed that non-nephritis patients had a similar burden of Type 2 SLE symptoms as patients with active nephritis, despite having on average lower Type 1 SLE activity. Therefore, the etiology of Type 2 SLE symptoms is likely multifactorial and may be driven by inflammatory and non-inflammatory biopsychosocial factors. Key Points • Patients with active nephritis experienced significant Type 2 symptoms that may be ameliorated as nephritis improves. • Non-nephritis patients had a similar burden of Type 2 SLE symptoms as patients with active nephritis, despite having on average lower Type 1 SLE activity. • Because etiology of Type 2 SLE symptoms is likely multifactorial and may be driven by inflammatory and non-inflammatory biopsychosocial factors.

The Type 1 & 2 systemic lupus erythematosus model: Perspectives of people living with systemic lupus erythematosus.

OBJECTIVE: In the new Type 1 & 2 model for systemic lupus erythematosus (SLE), Type 1 SLE represents classic inflammatory manifestations, such as arthritis, while Type 2 SLE encompasses symptoms such as pain and fatigue where the relationship to inflammation is less clear. The objective of this study was to interview individuals living with SLE to determine the content and face validity of the Type 1 & 2 SLE model. METHODS: We conducted a qualitative study using semi-structured interviews with a purposeful sample of participants who met classification criteria for SLE. Participants were asked to describe their experiences with Type 1 & 2 SLE symptoms and treatments, and they indicated if and how their personal experiences aligned with the Type 1 & 2 SLE model. All interviews were audio-recorded and transcribed; applied thematic analysis identified the most frequent and salient themes. RESULTS: We interviewed 42 participants with SLE. Type 2 SLE symptoms, such as pain and fatigue, were very common, with almost all participants experiencing some Type 2 symptoms at some point during their disease course. Participants described Type 1 SLE symptoms as being acute flares and life-threatening and Type 2 SLE symptoms as "everyday lupus" that affected their daily lives and were a dominant part of their SLE disease experience. Most participants stated they want their rheumatologists to discuss Type 2 symptoms during clinical appointments in order to address their full symptom experience. CONCLUSION: We demonstrated content and face validity of the Type 1 & 2 SLE model with people living with SLE. Participants in our study largely understood the model and felt it accurately reflected their experience living with SLE. Type 2 SLE symptoms are very common in individuals with SLE and impact patients' quality of life. Using the model to address Type 2 SLE symptoms allows the rheumatologist to incorporate the patient's perspective and provide patient-centered care.

Development and psychometric evaluation of a physician global assessment for type 2 systemic lupus erythematosus symptoms.

OBJECTIVE: Manifestations of SLE can be categorised as type 1 (classic signs and symptoms of SLE) or type 2 (fatigue, widespread pain and brain fog with an unclear relationship to inflammation). While measures of type 1 SLE activity exist, most current physician-reported measures do not encompass type 2 SLE manifestations. To better evaluate type 2 SLE symptoms, we developed and psychometrically evaluated a physician-reported measure of type 2 symptoms, the Type 2 Physician Global Assessment ('Type 2 PGA'). METHODS AND ANALYSIS: The Type 2 PGA was developed and evaluated by six rheumatologists practising in the same academic lupus clinic. The study began with a roundtable discussion to establish consensus guidelines for scoring the Type 2 PGA. Following the roundtable, the Type 2 PGA was psychometrically evaluated using data prospectively collected from 263 patients with SLE enrolled in the Duke Lupus Registry. RESULTS: There was strong intra-rater and inter-rater reliability (intraclass correlation coefficient=0.83), indicating the Type 2 PGA scores were consistent within a rheumatologist and across rheumatologists. The Type 2 PGA was correlated with patient-reported symptoms of polysymptomatic distress (r=0.76), fatigue (r=0.68), cognitive dysfunction (r=0.63), waking unrefreshed (r=0.62) and forgetfulness (r=0.60), and weakly correlated with the Type 1 PGA and the Systemic Lupus Erythematosus Disease Activity Index. CONCLUSION: The Type 2 PGA performed well as a physician-reported measure of type 2 SLE symptoms. The incorporation of the Type 2 PGA into a routine rheumatology visit may improve patient care by bringing the provider's attention to certain symptoms not well represented in conventional measures of disease activity.

Patient and physician perspectives of systemic lupus erythematosus flare: A qualitative study.

OBJECTIVE: Systemic lupus erythematosus (SLE) flares are associated with increased damage and decreased health-related quality of life. We hypothesized there is discordance between physicians' and patients' views of lupus flare. In this study, we aimed to explore patient and physician descriptions of SLE flares. METHODS: We conducted a qualitative descriptive study using in-depth interviews with a purposeful sample of patients with SLE (1997 ACR or SLICC criteria) and practicing rheumatologists. Interviews were audio-recorded, transcribed, and analyzed using applied thematic analysis. RESULTS: Forty-two patient participants living with SLE, representing a range of lupus activity, completed interviews. The majority described flare symptoms as joint pain, fatigue, and skin issues lasting several days. Few included objective signs or laboratory measures, when available, as features of flare.We interviewed 13 rheumatologists from 10 academic and 3 community settings. The overwhelming majority defined flare as increased or worsening lupus disease activity with slightly more than half requiring objective findings. Around half of the rheumatologists included fatigue, pain or other patient-reported symptoms. CONCLUSION: Patients and physicians described flare differently. Participants with SLE perceive flares as several days of fatigue, pain, and features. Providers define flares as periods of increased clinical SLE activity. Our findings suggest the current definition of flare may be insufficient to integrate both perceptions. Further study is needed to understand the pathophysiology of patient flares and the best way to incorporate patients' perspectives into clinical assessments.

Using PROMIS-29 to determine symptom burdens in the context of the Type 1 and 2 systemic lupus erythematosus (SLE) model: a cross sectional study.

OBJECTIVE: To account for heterogeneity in systemic lupus erythematosus (SLE) and bridge discrepancies between patient- and physician-perceived SLE activity, we developed the Type 1 and 2 SLE model. We examined PROMIS-29 scores, a composite patient-reported outcome (PRO) measure, through the lens of the model. METHODS: Patients completed PROMIS-29 and the polysymptomatic distress scale (PSD). Rheumatologists completed the SLE disease activity index (SLEDAI), and physician's global assessments (PGAs) for Type 1 and 2 SLE. We defined Type 1 SLE using SLEDAI, Type 1 PGA, and active nephritis, and Type 2 SLE using PSD and Type 2 PGA. We compared PROMIS-29 T-scores among Type 1 and 2 SLE groups and explored whether PROMIS-29 can predict Type 1 and 2 SLE activity. RESULTS: Compared to the general population, patients with isolated Type 1 SLE reported greater pain and physical dysfunction but less depression and improved social functions; patients with high Type 2 SLE (irrespective of Type 1 activity) reported high levels of pain, fatigue, and social and physical limitations. Patients with minimal Type 1 and 2 SLE had less depression and greater physical functioning with other domains similar to national norms. PROMIS-29 predicted Type 2 but not Type 1 SLE activity. CONCLUSION: PROMIS-29 similarities in patients with high Type 2 SLE, with and without active Type 1 SLE, demonstrate the challenges of using PROs to assess SLE inflammation. In conjunction with the Type 1 and 2 SLE model, however, PROMIS-29 identified distinct symptom patterns, suggesting that the model may help clinicians interpret PROs.

2023 International Consensus Guidance for the use of Tripterygium Wilfordii Hook F in the treatment of active rheumatoid arthritis.

BACKGROUND: Rheumatoid arthritis (RA) is a chronic autoimmune disorder that affects the joints and produces pain, swelling, and stiffness. It has a lifetime prevalence of up to 1% worldwide. An extract of Tripterygium wilfordii Hook F (TwHF), a member of the Celastraceae herbal family widely available in south China, has been used for treatment of RA since 1960s. METHODS: The current consensus practice guidance (CPG) aims to offer guidance on the application of TwHF in the clinical management of active RA. The CPG followed World Health Organisation (WHO)'s recommended process, carried out three systematic reviews to synthesize data from 19 randomised controlled trials (RCT) involving 1795 participants. We utilized Grading of Recommendations, Assessment, Development and Evaluation (GRADE) to evaluate certainty of evidence and derive recommendations. We rigorously followed The Appraisal of Guidelines for Research and Evaluation II (AGREE II) as conduct guides to minimise bias and promote transparency. RESULTS: There was no obvious difference between TwHF monotherapy and methotrexate (MTX) monotherapy on ACR20 (RCT = 2, N = 390, RR = 1.06, 95%CI 0.90-1.26, moderate certainty), ACR50 (RCT = 3, N = 419, RR = 1.03, 95%CI 0.80-1.34, moderate certainty), ACR70 (RCT = 2, N = 390, RR = 1.12, 95%CI 0.69-1.79, low certainty). TwHF monotherapy may be better than salicylazosulfapyridine monotherapy on ACR20 and the effect may be similar on ACR50 and ACR70. Seven RCTs compared MTX combined with TwHF versus MTX monotherapy, and the meta-analysis results favoured combination therapy group on ACR20 (RCT = 3, N = 470, RR = 1.44, 95%CI 1.28-1.62, moderate certainty), ACR50 (RCT = 4, N = 500, RR = 1.88, 95%CI 1.56-2.28, moderate certainty) and ACR70 (RCT = 2, N = 390, RR = 2.12, 95%CI 1.40-3.19, low certainty). We found no obvious difference between groups on critical safety outcomes, including infection (RCT = 3, N = 493, RR = 1.37, 95%CI 0.84-2.23), liver dysfunction (RCT = 5, N = 643, RR = 1.14, 95%CI 0.71-1.85), renal damage (RCT = 3, N = 450, RR = 2.20, 95%CI 0.50-9.72). CONCLUSION: Upon full review of the evidence, the guidance panel reached consensus on recommendations for the use of TwHF in people with active RA, either as monotherapy or as combination therapy with MTX.

The expression of antibodies to Z-DNA in the blood of patients with systemic lupus erythematosus: Relationship to autoantibodies to B-DNA.

To explore the antibody response to Z-DNA, a DNA conformation with a zig-zag structure, blood of patients with systemic lupus erythematosus (SLE) and otherwise healthy individuals (NHS) were assayed by ELISA using brominated poly(dGdC), a synthetic Z-DNA antigen. These studies showed that SLE patients commonly express antibodies to Z-DNA; NHS also had binding in this assay. In SLE blood, levels of antibodies to Z-DNA were related to those to B-DNA using calf thymus DNA as a source of B-DNA; cross-reactivity was demonstrated by adsorption experiments using DNA cellulose. As shown by dissociation assays, antibody binding of SLE anti-Z-DNA is sensitive to the effects of ionic strength, suggesting electrostatic binding. Since Z-DNA structure can be found in bacterial DNA as well as bacterial biofilms, these findings suggest that, in SLE, anti-DNA antibody responses can result from stimulation by DNA of bacterial origin, with cross-reactivity leading to autoreactivity.

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

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

In relapsing AAV with rituximab-induced remission, maintenance rituximab vs. azathioprine reduced relapse at ≥32 mo.

SOURCE CITATION: Smith RM, Jones RB, Specks U, et al; RITAZAREM co-investigators. Rituximab versus azathioprine for maintenance of remission for patients with ANCA-associated vasculitis and relapsing disease: an international randomised controlled trial. Ann Rheum Dis. 2023;82:937-944. 36958796.

Pathogenesis of autoimmune disease.

Autoimmune diseases are a diverse group of conditions characterized by aberrant B cell and T cell reactivity to normal constituents of the host. These diseases occur widely and affect individuals of all ages, especially women. Among these diseases, the most prominent immunological manifestation is the production of autoantibodies, which provide valuable biomarkers for diagnosis, classification and disease activity. Although T cells have a key role in pathogenesis, they are technically more difficult to assay. In general, autoimmune disease results from an interplay between a genetic predisposition and environmental factors. Genetic predisposition to autoimmunity is complex and can involve multiple genes that regulate the function of immune cell populations. Less frequently, autoimmunity can result from single-gene mutations that affect key regulatory pathways. Infection seems to be a common trigger for autoimmune disease, although the microbiota can also influence pathogenesis. As shown in seminal studies, patients may express autoantibodies many years before the appearance of clinical or laboratory signs of disease - a period called pre-clinical autoimmunity. Monitoring autoantibody expression in at-risk populations may therefore enable early detection and the initiation of therapy to prevent or attenuate tissue damage. Autoimmunity may not be static, however, and remission can be achieved by some patients treated with current agents.

Moonlighting chromatin: when DNA escapes nuclear control.

Extracellular chromatin, for example in the form of neutrophil extracellular traps (NETs), is an important element that propels the pathological progression of a plethora of diseases. DNA drives the interferon system, serves as autoantigen, and forms the extracellular scaffold for proteins of the innate immune system. An insufficient clearance of extruded chromatin after the release of DNA from the nucleus into the extracellular milieu can perform a secret task of moonlighting in immune-inflammatory and occlusive disorders. Here, we discuss (I) the cellular events involved in the extracellular release of chromatin and NET formation, (II) the devastating consequence of a dysregulated NET formation, and (III) the imbalance between NET formation and clearance. We include the role of NET formation in the occlusion of vessels and ducts, in lung disease, in autoimmune diseases, in chronic oral disorders, in cancer, in the formation of adhesions, and in traumatic spinal cord injury. To develop effective therapies, it is of utmost importance to target pathways that cause decondensation of chromatin during exaggerated NET formation and aggregation. Alternatively, therapies that support the clearance of extracellular chromatin are conceivable.

In glucocorticoid-dependent polymyalgia rheumatica, tocilizumab improved a composite clinical outcome at 24 wk.

SOURCE CITATION: Devauchelle-Pensec V, Carvajal-Alegria G, Dernis E, et al. Effect of tocilizumab on disease activity in patients with active polymyalgia rheumatica receiving glucocorticoid therapy: a randomized clinical trial. JAMA. 2022;328:1053-62. 36125471.

Efficacy and Safety of the Bruton's Tyrosine Kinase Inhibitor Evobrutinib in Systemic Lupus Erythematosus: Results of a Phase II, Randomized, Double-Blind, Placebo-Controlled Dose-Ranging Trial.

OBJECTIVE: Evobrutinib is a highly selective, orally administered Bruton's tyrosine kinase (BTK) inhibitor. The objective of this phase II, multicenter, randomized, double-blind, placebo-controlled trial was to evaluate the efficacy and safety of evobrutinib in patients with active autoantibody-positive systemic lupus erythematosus (SLE). METHODS: Patients were diagnosed with SLE by either the Systemic Lupus International Collaborating Clinics criteria or at least four American College of Rheumatology criteria 6 months or more prior to screening, had an SLE Disease Activity Index-2000 score of 6 or more, were autoantibody-positive and on standard-of-care therapy. Randomization was 1:1:1:1 to oral evobrutinib 25 mg once daily (QD), 75 mg QD, 50 mg twice daily, or placebo. Primary efficacy endpoints were SLE responder index (SRI)-4 response at week 52 and SRI-6 response at week 52 in the high disease activity subpopulation. Safety endpoints included treatment-emergent adverse events (TEAEs). RESULTS: A total of 469 patients were randomized and received at least one dose of evobrutinib or placebo at the time of primary analysis. Mean (SD) age at baseline was 40.7 (±12.3) years; 94.9% of patients were female. Neither primary efficacy endpoint was met. All doses of evobrutinib were well tolerated, and there was no clear dose effect on the incidence of reported TEAEs, or serious TEAEs, including severe infections. CONCLUSION: This phase II, dose-ranging trial in SLE failed to show a treatment effect of evobrutinib versus placebo at any dose. Evobrutinib was generally well tolerated, with no dose effect observed for TEAEs. These results suggest that BTK inhibition does not appear to be an effective therapeutic intervention for patients with SLE.

Artificial intelligence and high-dimensional technologies in the theragnosis of systemic lupus erythematosus.

Systemic lupus erythematosus is a complex, systemic autoimmune disease characterised by immune dysregulation. Pathogenesis is multifactorial, contributing to clinical heterogeneity and posing challenges for diagnosis and treatment. Although strides in treatment options have been made in the past 15 years, with the US Food and Drug Administration approval of belimumab in 2011, there are still many patients who have inadequate responses to therapy. A better understanding of underlying disease mechanisms with a holistic and multiparametric approach is required to improve clinical assessment and treatment. This Review discusses the evolution of genomics, epigenomics, transcriptomics, and proteomics in the study of systemic lupus erythematosus and ways to amalgamate these silos of data with a systems-based approach while also discussing ways to strengthen the overall process. These mechanistic insights will facilitate the discovery of functionally relevant biomarkers to guide rational therapeutic selection to improve patient outcomes.

Mixed-surface polyamidoamine polymer variants retain nucleic acid-scavenger ability with reduced toxicity.

Nucleic acid-binding polymers can have anti-inflammatory properties and beneficial effects in animal models of infection, trauma, cancer, and autoimmunity. PAMAM G3, a polyamidoamine dendrimer, is fully cationic bearing 32 protonable surface amines. However, while PAMAM G3 treatment leads to improved outcomes for mice infected with influenza, at risk of cancer metastasis, or genetically prone to lupus, its administration can lead to serosal inflammation and elevation of biomarkers of liver and kidney damage. Variants with reduced density of cationic charge through the interspersal of hydroxyl groups were evaluated as potentially better-tolerated alternatives. Notably, the variant PAMAM G3 50:50, similar in size as PAMAM G3 but with half the charge, was not toxic in cell culture, less associated with weight loss or serosal inflammation after parenteral administration, and remained effective in reducing glomerulonephritis in lupus-prone mice. Identification of such modified scavengers should facilitate their development as safe and effective anti-inflammatory agents.

The Interaction of Anti-DNA Antibodies with DNA: Evidence for Unconventional Binding Mechanisms.

Antibodies to DNA (anti-DNA) are the serological hallmark of systemic lupus erythematosus, a prototypic autoimmune disease. These antibodies bind to conserved sites on single-stranded and double-stranded DNA and display variable region somatic mutations consistent with antigen selection. Nevertheless, the interaction of anti-DNA with DNA has unconventional features. Anti-DNA antibodies bind by a mechanism called monogamous bivalency, in which stable interaction requires contact of both Fab sites with determinants on the same extended DNA molecule; the size of this DNA can be hundreds to thousands of bases, especially in solid phase assays. This binding also requires the presence of the Fc portion of IgG, a binding mechanism known as Fc-dependent monogamous bivalency. As shown by the effects of ionic strength in association and dissociation assays, anti-DNA binding is primarily electrostatic. Like anti-DNA autoantibodies, anti-DNA antibodies that bind specifically to non-conserved sites on bacterial DNA, a type of anti-DNA found in otherwise healthy individuals, also interact by monogamous bivalency. The unconventional features of anti-DNA antibodies may reflect the highly charged and polymeric nature of DNA and the need for molecular rearrangements to facilitate monogamous bivalency; the Fc portion contributes to binding in an as yet unknown way.