Presence of antinucleosome autoantibodies in a restricted set of connective tissue diseases: antinucleosome antibodies of the IgG3 subclass are markers of renal pathogenicity in systemic lupus erythematosus

Assessment of anti-nucleosome antibody (ANuA) isotypes for the diagnosis and prediction of systemic lupus erythematosus and lupus nephritis activity

Our study aims to investigate the serum levels of anti-nucleosome antibody (ANuA) isotypes in patients with systemic lupus erythematosus (SLE) and clarify ANuA isotypes that may diagnose and predict SLE. We detected anti-nucleosome antibodies (ANuA) in the serum from 120 patients with SLE, 99 patients suffering from other autoimmune diseases (OAD), and 50 healthy controls by performing IgG-, IgA-, and IgM-specific ELISAs. The serum levels of total anti-nuclear antibodies (ANA IgG), ANuA IgG subclasses (IgG1, IgG2, IgG3, and IgG4), anti-dsDNA antibodies, and the avidities of ANA IgG were also analysed using ELISAs. The levels of three ANuA isotypes (IgG, IgA, and IgM) were significantly higher in patients with SLE than in patients with OAD and healthy controls (p < 0.05). Moreover, the concentrations of ANuA isotypes increased in the active SLE and lupus nephritis (LN) groups and in patients with SLE presenting high-avidity IgG ANA (p < 0.05). Furthermore, ANuA isotype levels decreased significantly with drug therapy, while anti-dsDNA IgG levels decreased with the same trend. Additionally, ANuA isotypes were positively related to the SLEDAI (SLE Disease Activity Index) score, RAI (relative avidity index) of high-avidity IgG ANAs, and serum anti-dsDNA IgG levels. Last, the sensitivity and specificity values for SLE were 83.33 and 96.67% for ANuA IgG, 85.83 and 93.33% for ANuA IgA, and83.33 and 86.67% for ANuA IgM, respectively. The sensitivity and specificity values for LN were 61.67 and 96.67% for ANuA IgG, 49.17 and 96.67% for ANuA IgA, and 52.50 and 96.67% for ANuA IgM, respectively. In conclusion, we evaluated whether ANuA isotypes represent a diagnostic tool to predict SLE activity and define subsets of patients with LN.

Increased Immunoglobulin Gamma-3 Chain C in the Serum, Saliva, and Urine of Patients with Systemic Lupus Erythematosus

Immunoglobulin gamma-3 chain C (IGHG3) levels have been detected in the blood and tissue of patients with systemic lupus erythematosus (SLE). This study aims to assess its clinical value by measuring and comparing levels of IGHG3 in different body fluids in patients with SLE. The levels of IGHG3 in saliva, serum, and urine from 181 patients with SLE and 99 healthy controls were measured and analyzed. In patients with SLE and healthy controls, salivary IGHG3 levels were 3078.9 ± 2473.8 and 1413.6 ± 1075.3 ng/mL, serum IGHG3 levels were 478.1 ± 160.9 and 364.4 ± 97.9 μg/mL, and urine IGHG3 levels were 64.0 ± 74.5 and 27.1 ± 16.2 ng/mL, respectively (all p < 0.001). Salivary IGHG3 was correlated with ESR (correlation coefficient [r], 0.173; p = 0.024). Serum IGHG3 was correlated with leukocyte count (r, -0.219; p = 0.003), lymphocyte count (r, 0.22; p = 0.03), anti-dsDNA antibody positivity (r, 0.22; p = 0.003), and C3 levels (r, -0.23; p = 0.002). Urinary IGHG3 was correlated with hemoglobin level (r, -0.183; p = 0.021), ESR (r, 0.204; p = 0.01), anti-dsDNA antibody positivity (r, 0.262; p = 0.001), C3 levels (r, -0.202; p = 0.011), and SLE disease activity index (r, 0.332; p = 0.01). Urinary IGHG3 was higher in patients with nephritis than in those without (119.5 ± 110.0 vs. 49.8 ± 54.4 ng/mL; p < 0.01). IGHG3 was increased in the saliva, serum, and urine of patients with SLE. While salivary IGHG3 was not identified to be specific to SLE disease activity, serum IGHG3 showed correlations with clinical characteristics. Urinary IGHG3 levels were associated with disease activity and renal involvement in SLE.

Polymorphonuclear Neutrophils in Rheumatoid Arthritis and Systemic Lupus Erythematosus: More Complicated Than Anticipated

Polymorphonuclear neutrophils (PMN) are the most abundant leucocytes in the circulation in humans. They represent a heterogeneous population exerting diverse functions through several activities. Usually described as typical pro-inflammatory cells, immunomodulatory properties of PMNs have been reported. Among others, once activated and depending on the stimulus, PMNs expel neutrophil extracellular traps (NET) in the extracellular space. NETs are complexes made of DNA and granule proteins representing an innate immune mechanism fighting infections. Nevertheless, an excess of NET formation might be involved in the development of inflammatory or autoimmune responses. Systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA) are two chronic, inflammatory, autoimmune diseases of unknown etiology and affecting mostly women. Several abnormal or non-classical functions of PMNs or PMN sub-populations have been described in SLE and RA. Particularly, NETs have been suggested to trigger pro-inflammatory responses by exposing pro-inflammatory mediators. Likewise, NETs may be the targets of autoantibodies or even might trigger the development of autoantibodies by exposing autoantigens. In the present review, we will summarize heterogeneous properties of human PMNs and we will discuss recent evidence linking PMNs and NETs to the pathogenesis of both SLE and RA.

Neutrophil Extracellular Traps-DNase Balance and Autoimmunity

Neutrophil extracellular traps (NETs) are macromolecular structures programmed to trap circulating bacteria and viruses. The accumulation of NETs in the circulation correlates with the formation of anti-double-stranded (ds) DNA antibodies and is considered a causative factor for systemic lupus erythematosus (SLE). The digestion of DNA by DNase1 and DNases1L3 is the rate- limiting factor for NET accumulation. Mutations occurring in one of these two DNase genes determine anti-DNA formation and are associated with severe Lupus-like syndromes and lupus nephritis (LN). A second mechanism that may lead to DNase functional impairment is the presence of circulating DNase inhibitors in patients with low DNase activity, or the generation of anti-DNase antibodies. This phenomenon has been described in a relevant number of patients with SLE and may represent an important mechanism determining autoimmunity flares. On the basis of the reviewed studies, it is tempting to suppose that the blockade or selective depletion of anti-DNase autoantibodies could represent a potential novel therapeutic approach to prevent or halt SLE and LN. In general, strategies aimed at reducing NET formation might have a similar impact on the progression of SLE and LN.

Clinical and serological associations of autoantibodies in patients with systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is an autoimmune disorder characterized by the formation of antigen-antibody complexes which trigger an immune response. We investigate certain autoantibodies including nucleosome, double-stranded DNA (dsDNA), Smith, ribonucleoprotein, and Sjögren's syndrome-related antigens, and examine their associations with disease activity, damage accrual, and SLE-related clinical and serological manifestations in patients with SLE. We conducted a cross-sectional study with a total 293 patients (90.4% female, mean age 46.87±12.94 years) and used the Systemic Lupus Erythematosus Disease Activity Index 2000 and Systemic Lupus International Collaborating Clinics/American College of Rheumatology Damage Index (SDI) to evaluate disease activity and disease-related damage, respectively. Systemic Lupus Erythematosus Disease Activity Index scores were significantly higher in anti-nucleosome-positive (3.87±2.72 vs 2.52±2.76, p=0.004) and anti-dsDNA-positive (3.08±2.91 vs 2.04±2.48, p=0.010) patients compared with patients without these antibodies. SDI scores were also significantly higher in anti-nucleosome-positive patients (1.61±1.99 vs 0.89±1.06, p=0.004). The presence of antinucleosome (p=0.019) and anti-dsDNA antibodies (p=0.001) both correlated significantly with the incidence of nephritis; anti-La antibodies were associated with arthritis (p=0.022), and we also observed a relationship between the presence of antinucleosome antibodies and leukopenia (p=0.011). Patients with antinucleosome or anti-dsDNA antibodies had a higher disease activity and were likely to have nephritis. Antinucleosome was also associated with more damage accrual. A greater understanding of these autoantibodies could lead to the development of new approaches to more accurate assessments of SLE.

Increased Concentrations of Circulating Soluble MHC Class I-Related Chain A (sMICA) and sMICB and Modulation of Plasma Membrane MICA Expression: Potential Mechanisms and Correlation With Natural Killer Cell Activity in Systemic Lupus Erythematosus

Systemic lupus erythematosus (SLE) is a severe autoimmune disease of unknown etiology. The major histocompatibility complex (MHC) class I-related chain A (MICA) and B (MICB) are stress-inducible cell surface molecules. MICA and MICB label malfunctioning cells for their recognition by cytotoxic lymphocytes such as natural killer (NK) cells. Alterations in this recognition have been found in SLE. MICA/MICB can be shed from the cell surface, subsequently acting either as a soluble decoy receptor (sMICA/sMICB) or in CD4⁺ T-cell expansion. Conversely, NK cells are frequently defective in SLE and lower NK cell numbers have been reported in patients with active SLE. However, these cells are also thought to exert regulatory functions and to prevent autoimmunity. We therefore investigated whether, and how, plasma membrane and soluble MICA/B are modulated in SLE and whether they influence NK cell activity, in order to better understand how MICA/B may participate in disease development. We report significantly elevated concentrations of circulating sMICA/B in SLE patients compared with healthy individuals or a control patient group. In SLE patients, sMICA concentrations were significantly higher in patients positive for anti-SSB and anti-RNP autoantibodies. In order to study the mechanism and the potential source of sMICA, we analyzed circulating sMICA concentration in Behcet patients before and after interferon (IFN)-α therapy: no modulation was observed, suggesting that IFN-α is not intrinsically crucial for sMICA release in vivo. We also show that monocytes and neutrophils stimulated in vitro with cytokines or extracellular chromatin up-regulate plasma membrane MICA expression, without releasing sMICA. Importantly, in peripheral blood mononuclear cells from healthy individuals stimulated in vitro by cell-free chromatin, NK cells up-regulate CD69 and CD107 in a monocyte-dependent manner and at least partly via MICA-NKG2D interaction, whereas NK cells were exhausted in SLE patients. In conclusion, sMICA concentrations are elevated in SLE patients, whereas plasma membrane MICA is up-regulated in response to some lupus stimuli and triggers NK cell activation. Those results suggest the requirement for a tight control in vivo and highlight the complex role of the MICA/sMICA system in SLE.

Deoxyribonuclease 1-Mediated Clearance of Circulating Chromatin Prevents From Immune Cell Activation and Pro-inflammatory Cytokine Production, a Phenomenon Amplified by Low Trap1 Activity: Consequences for Systemic Lupus Erythematosus

Increased concentrations of circulating chromatin, especially oligo-nucleosomes, are observed in sepsis, cancer and some inflammatory autoimmune diseases like systemic lupus erythematosus (SLE). In SLE, circulating nucleosomes mainly result from increased apoptosis and decreased clearance of apoptotic cells. Once released, nucleosomes behave both as an autoantigen and as a damage-associated molecular pattern (DAMP) by activating several immune cells, especially pro-inflammatory cells. Deoxyribonuclease 1 (DNase1) is a major serum nuclease whose activity is decreased in mouse and human lupus. Likewise, the mitochondrial chaperone tumor necrosis factor (TNF) receptor-associated protein-1 (Trap1) protects against oxidative stress, which is increased in SLE. Here, using wild type, DNase1-deficient and DNase1/Trap1-deficient mice, we demonstrate that DNase1 is a major serum nuclease involved in chromatin degradation, especially when the plasminogen system is activated. In vitro degradation assays show that chromatin digestion is strongly impaired in serum from DNase1/Trap1-deficient mice as compared to wild type mice. In vivo, after injection of purified chromatin, clearance of circulating chromatin is delayed in DNase1/Trap1-deficient mice in comparison to wild type mice. Since defective chromatin clearance may lead to chromatin deposition in tissues and subsequent immune cell activation, spleen cells were stimulated in vitro with chromatin. Splenocytes were activated by chromatin, as shown by interleukin (IL)-12 secretion and CD69 up-regulation. Moreover, cell activation was exacerbated when Trap1 is deficient. Importantly, we also show that cytokines involved in lupus pathogenesis down-regulate Trap1 expression in splenocytes. Therefore, combined low activities of both DNase1 and Trap1 lead to an impaired degradation of chromatin in vitro, delayed chromatin clearance in vivo and enhanced activation of immune cells. This situation may be encountered especially, but not exclusively, in SLE by the negative action of cytokines on Trap1 expression.

Enhanced migration and adhesion of peripheral blood neutrophils from SAPHO patients revealed by RNA-Seq

Background

SAPHO syndrome is a rare disease characterized by inflammatory lesions on skin and bones. Diversified manifestation and inadequate understanding of etiology has limited its diagnosis and treatment. The co-occurrence of other immune-mediated diseases strongly suggests an involvement of autoimmunity in SAPHO syndrome. However, the role of the largest population of circulating immune cells, neutrophils, is still not well explored. In this study, we performed RNA sequencing to profile the mRNA expression of neutrophils purified from peripheral blood of SAPHO patients to identify key genes associated with SAPHO syndrome, trying to find new functional molecules or biomarkers for this rare disease.

Results

A total of 442 differentially expressed genes were identified (p < 0.05, fold change > 2), in which 294 genes were upregulated and 148 genes were downregulated. Five differentially expressed genes of interest were verified by quantitative Real-Time Polymerase Chain Reaction (qRT-PCR), among which S100A12 was upregulated and positively related to high-sensitivity C-reactive protein (hsCRP), while the downregulated gene MYADM was positively related to osteocalcin. Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis showed that differentially expressed genes were enriched in “systemic lupus erythematosus” and “ECM-receptor interaction”. Gene ontology (GO) enrichment showed that differentially expressed genes may participate in biological processes such as “cell migration” and “cell adhesion”.

Conclusions

In conclusion, this study provides a first insight into transcriptome characteristics of SAPHO syndrome, indicating an over-active neutrophil recruitment in patients and possibly suggesting molecular candidates for further study on diagnosis and pathology of this disease.

Electronic supplementary material

The online version of this article (10.1186/s13023-019-1169-3) contains supplementary material, which is available to authorized users.

Neutrophil Extracellular Traps in the Establishment and Progression of Renal Diseases

Uncontrolled inflammatory and immune responses are often involved in the development of acute and chronic forms of renal injury. Neutrophils are innate immune cells recruited early to sites of inflammation, where they produce pro-inflammatory cytokines and release mesh-like structures comprised of DNA and granular proteins known as neutrophil extracellular traps (NETs). NETs are potentially toxic, contribute to glomerular injury, activate autoimmune processes, induce vascular damage, and promote kidney fibrosis. Evidence from multiple studies suggests that an imbalance between production and clearance of NETs is detrimental for renal health. Hence strategies aimed at modulating NET-associated processes could have a therapeutic impact on a myriad of inflammatory diseases that target the kidney. Here, we summarize the role of NETs in the pathogenesis of renal diseases and their mechanisms of tissue damage.

Extracellular Chromatin Triggers Release of Soluble CEACAM8 Upon Activation of Neutrophils

Increased concentrations of extracellular chromatin are observed in cancer, sepsis, and inflammatory autoimmune diseases like systemic lupus erythematosus (SLE) or rheumatoid arthritis (RA). In SLE and RA, extracellular chromatin may behave as a danger-associated molecular pattern (DAMP). Polymorphonuclear neutrophils (PMN) are described as typical pro-inflammatory cells but possess also immunoregulatory properties. They are activated in SLE and RA but surprisingly remain moderately studied in these diseases, and especially the disease-associated stimuli triggering PMN activation are still not completely characterized. PMN express plasma membrane carcinoembryonic antigen-related cell adhesion molecule (CEACAM) 8 (CD66b) and secrete a soluble form of CEACAM8 after activation. Soluble CEACAM8 has in turn immunoregulatory functions. However, few natural stimuli inducing soluble CEACAM8 secretion by PMN have been identified. Here we demonstrate for the first time that extracellular chromatin triggers secretion of soluble CEACAM8 by primary human PMN. Priming of PMN was not required. Secretion was associated with activation of PMN. Similar induction of soluble CEACAM8 release was observed with purified mono-nucleosomes as well as long chromatin fragments and occurred in a time-dependent and concentration-dependent manner. Results indicate that chromatin induces both neo-synthesis of soluble CEACAM8 and release of soluble CEACAM8 through degranulation. In addition, we report the presence of soluble CEACAM8 at high concentration in the synovial fluid of RA patients. Thus, we describe here a novel mechanism by which a natural DAMP, with inflammatory properties in SLE and RA, induces soluble CEACAM8 secretion by activated PMN with potential immunoregulatory consequences on other immune cells, including PMN.

Antiphospholipid Antibodies to Domain I of Beta-2-Glycoprotein I Show Different Subclass Predominance in Comparison to Antibodies to Whole Beta-2-glycoprotein I

Antiphospholipid antibodies (aPL), the serological hallmark of antiphospholipid syndrome (APS), are a heterogeneous group of autoantibodies raised against circulating blood proteins. Of these proteins, the phospholipid-binding b2-glycoprotein I (β2GPI) is considered to be the main autoantigen in APS. Indeed, IgG antibodies targeting b2GPI (ab2GPI) directly cause both thrombosis and pregnancy morbidity in several mouse models. While antibodies raised against all five domains of b2GPI have been reported, a subgroup of IgG ab2GPI raised against the first domain (DI) of b2GPI (aDI), strongly correlate with thrombotic APS, and drive thrombosis and pregnancy loss in vivo. Few studies have focused on determining the type of IgG subclass(es) for aPL. The subclass of an antibody is important as this dictates the potential activity of an antibody; for example, IgG1 and IgG3 can fix complement better and are able to cross the placenta compared to IgG2 and IgG4. It is unknown what subclass IgG aDI are, and whether they are the same as ab2GPI. To determine IgG subclass distribution for ab2GPI and aDI, we purified total IgG from the serum of 19 APS patients with known ab2GPI and aDI activity. Using subclass-specific conjugated antibodies, we modified our established in-house ab2GPI and aDI ELISAs to individually measure IgG1, IgG2, IgG3, and IgG4. We found that while IgG1, IgG2, and IgG3 ab2GPI levels were similar, a marked difference was seen in IgG subclass aDI levels. Specifically, significantly higher levels of IgG3 aDI were detected compared to IgG1, IgG2, or IgG4 (p < 0.05 for all comparisons). Correlation analysis of subclass-specific ab2GPI vs. aDI demonstrated that IgG3 showed the weakest correlation (r = 0.45, p = 0.0023) compared to IgG1 (r = 0.61, p = 0.0001) and IgG2 (r = 0.81, p = 0.0001). Importantly, total subclass levels in IgG purified from APS and healthy serum (n = 10 HC n = 12 APS) did not differ, suggesting that the increased IgG3 aDI signal seen in APS-derived IgG is antigen-specific. To conclude, our data suggests that aDI show a different IgG subclass distribution to ab2GPI. Our results highlight the importance of aDI testing for patient stratification and may point toward differential underlying aPL-driven pathogenic processes that may be subclass restricted.

Autoantibodies Associated With Connective Tissue Diseases: What Meaning for Clinicians?

Connective tissue diseases (CTDs) such as systemic lupus erythematosus, systemic sclerosis, myositis, Sjögren's syndrome, and rheumatoid arthritis are systemic diseases which are often associated with a challenge in diagnosis. Autoantibodies (AAbs) can be detected in these diseases and help clinicians in their diagnosis. Actually, pathophysiology of these diseases is associated with the presence of antinuclear antibodies. In the last decades, many new antibodies were discovered, but their implication in pathogenesis of CTDs remains unclear. Furthermore, the classification of these AAbs is nowadays misused, as their targets can be localized outside of the nuclear compartment. Interestingly, in most cases, each antibody is associated with a specific phenotype in CTDs and therefore help in better defining either the disease subtypes or diseases activity and outcome. Because of recent progresses in their detection and in the comprehension of their pathogenesis implication in CTD-associated antibodies, clinicians should pay attention to the presence of these different AAbs to improve patient's management. In this review, we propose to focus on the different phenotypes and features associated with each autoantibody used in clinical practice in those CTDs.

Flares in systemic lupus erythematosus: diagnosis, risk factors and preventive strategies

Despite advances in the treatment, patients with systemic lupus erythematosus (SLE) often experience disease exacerbations (flares) of varying severity. Their diagnosis is primarily made on clinical grounds after exclusion of other diseases or disturbances, primarily infections, and can be assisted by the use of validated clinical indices. Serological tests such as serum complement fractions and anti-dsDNA autoantibodies, are helpful in monitoring SLE activity, but they lack high diagnostic accuracy. Flares are more frequent in patients with persistent immunological and clinical activity, and have been described as significant risk factor for development of irreversible end-organ damage. Accordingly, prevention of flares has been recognized as a distinct therapeutic target in SLE and involves adequate control of disease activity, use of hydroxychloroquine, maintaining immunosuppressive or biologic therapy for several years, and avoiding non-compliance issues. The future holds promise for the discovery of biomarkers that will accurately predict or diagnose SLE flares, thus allowing for the implementation of patient-tailored preventive strategies.

Pro-inflammatory S100 proteins are associated with glomerulonephritis and anti-dsDNA antibodies in systemic lupus erythematosus

Objectives Systemic lupus erythematosus (SLE) is associated with elevated levels of S100A8/A9, pro-inflammatory proteins mainly secreted by activated polymorphonuclear neutrophils (PMNs). The underlying mechanisms for increased S100A8/A9 levels and their relation to the clinical phenotype have not been carefully investigated. We assessed S100A8/A9 and S100A12 levels in SLE patient sera in relation to disease activity, clinical phenotype, presence of anti-dsDNA antibodies and ability to promote phagocytosis of necrotic cells (NCs) by PMNs. Methods Serum levels of S100A8/A9 and S100A12 were measured by ELISA in paired samples of 100 SLE patients at time points of higher and lower disease activity. Serum-mediated phagocytosis of NCs by PMNs was analysed by flow cytometry. Clinical data were recorded at time points of blood sampling. Results Serum levels of S100A8/A9 and S100A12 were increased in SLE patients with high disease activity compared to paired samples at low disease activity ( p = 0.01 and p = 0.008, respectively). Elevated levels of S100A8/A9 were particularly seen in patients with anti-dsDNA antibodies ( p = 0.01) and glomerulonephritis before treatment ( p = 0.02). Immunosuppressive therapy was associated with a reduction of S100A8/A9 serum levels ( p = 0.002). The ability of serum to support phagocytosis of NCs by PMNs was related to increased S100A8/A9 levels ( p = 0.01). Conclusions Elevated serum levels of S100A8/A9 may be used to monitor disease activity and response to treatment in SLE patients, especially in patients with glomerulonephritis. S100A12 may be a marker of disease activity in SLE. Increased S100A8/A9 levels may reflect immune-pathological processes involving phagocytosis of immune complexes by PMNs.

Antinucleosome Antibodies in Patients with Juvenile Systemic Lupus Erythematosus

Our objective was to evaluate the frequency of antinucleosome antibodies (anti-Ncs) in juvenile systemic lupus erythematosus (JSLE) comparing it to that observed for anti-DNA and to correlate the presence of these antibodies with clinical manifestations and disease activity. Anti-Ncs and anti-DNA were detected by ELISA in 74 patients with JSLE and 64 normal controls. Clinical records were reviewed. Disease activity was assessed by SLEDAI score. Anti-Ncs and anti-DNA showed sensitivity of 52.7% and 54% and specificity of 98.4% and 95.3%, respectively. Disagreement between the two assays was found in 25.7% of the cases: isolated positive Anti-Ncs in nine cases (12.2%) and isolated positive anti-DNA in 10 cases (13.5%). Agreement was found in 74.3%: both positive antibodies in 30 cases and both negative in 25. The presence of anti-Ncs was significantly associated with malar erythema, hemolytic anemia, anti-DNA and low complement levels, but not with renal manifestations. The presence of anti-Ncs was associated with a higher SLEDAI median ( P &lt; 0.001) and its titers correlated with the SLEDAI score ( r = 0.504; P &lt; 0.001). The frequency, sensitivity and specificity values were similar between anti-Ncs and anti-DNA antibodies in patients with JSLE. Nevertheless, the discordance of 25.7% between the two assays suggests that both antibodies may have a complementary diagnostic role. The association and correlation between anti-Ncs and several disease activity parameters demonstrated its usufulness in the follow-up of these patients.

Testing for anti-nucleosome antibodies in daily practice: a monocentric evaluation in 1696 patients

The objective was to report our experience of the detection of anti-nucleosome (anti-Nuc) antibodies (Ab) in a large series of consecutive patients, and to compare these results with those of anti-nuclear and anti-dsDNA Ab. In total, 1696 consecutive patients with suspected or confirmed autoimmune disease were tested over a two-year period. The biological investigation included detection of anti-nuclear, anti-dsDNA and anti-Nuc Ab. Among 1696 sera, 382 (23%) were negative for all Ab tested (anti-nuclear, anti-dsDNA and anti-Nuc) and 1314 (77%) were positive for at least one Ab. Anti-Nuc Ab were positive in 350/1314 patients. In this group, 249/350 (71%) also had positive anti-nuclear and anti-dsDNA, 97/350 (28%) had only positive anti-nuclear Ab without anti-dsDNA Ab and 4/350 (1%) had both anti-dsDNA and anti-Nuc Ab without anti-nuclear Ab. No patient had ‘isolated’ anti-Nuc Ab. Clinical data were available for 307/350 anti-Nuc positive patients. Systemic lupus erythematosus (SLE) was diagnosed in 240/307 (78%) patients, including 43 SLE patients with negative anti-dsDNA Ab. In conclusion, this study extends the relevance of anti-Nuc Ab to routine use for the diagnosis of connective tissue diseases, mainly anti-dsDNA Ab negative SLE.

Autoantibodies in SLE: Specificities, Isotypes and Receptors

Systemic Lupus Erythematosus (SLE) is characterized by a wide spectrum of auto-antibodies which recognize several cellular components. The production of these self-reactive antibodies fluctuates during the course of the disease and the involvement of different antibody-secreting cell populations are considered highly relevant for the disease pathogenesis. These cells are developed and stimulated through different ways leading to the secretion of a variety of isotypes, affinities and idiotypes. Each of them has a particular mechanism of action binding to a specific antigen and recognized by distinct receptors. The effector responses triggered lead to a chronic tissue inflammation. DsDNA autoantibodies are the most studied as well as the first in being characterized for its pathogenic role in Lupus nephritis. However, others are of growing interest since they have been associated with other organ-specific damage, such as anti-NMDAR antibodies in neuropsychiatric clinical manifestations or anti-β2GP1 antibodies in vascular symptomatology. In this review, we describe the different auto-antibodies reported to be involved in SLE. How autoantibody isotypes and affinity-binding to their antigen might result in different pathogenic responses is also discussed.

Novel Autoantigens Associated with Lupus Nephritis

Systemic lupus erythematosus (SLE) is characterized by production of a variety of autoantibodies. Although anti-double-stranded DNA (anti-dsDNA) antibodies contribute to the pathogenesis of lupus nephritis (LN), they are not sufficient for diagnosis and evaluation of disease activity. To obtain other autoantibodies associated with LN, we screened autoantigens reacting with the sera of LN patients by using an N-terminal biotinylated protein library created from a wheat cell-free protein production system. We screened 17 proteins that showed higher positive signals in the active phase than in the inactive phase of SLE, and higher positive signals in the serum of SLE patient with nephritis than in that of patient without nephritis. Of these, two LN-associated autoantigens, ribosomal RNA-processing protein 8 (RRP8) and spermatid nuclear transition protein 1 (TNP1) were identified by immunoprecipitation and immunofluorescence of renal tissues. Circulating anti-RRP8 and anti-TNP1 autoantibodies were recognized and deposited as an immune complex (IC) in glomeruli. IC was deposited preferentially in glomeruli rather than in other organs in C57BL/6 mice injected with RRP8 or TNP1. ELISA analysis of sera from patients with various rheumatic diseases demonstrated reactivity for RRP8 and TNP1 in 20% and 14.7% of SLE patients, respectively, whereas there was little or no reactivity in patients with other rheumatic diseases. Among SLE patients, 63.6% and 45.5% of those with LN were positive for anti-RRP8 and anti-TNP1 antibodies, compared with 12.5% and 9.4% of SLE patients without nephritis, respectively. Both proteins are cationic, and their respective antibodies did not cross-react with dsDNA. These proteins released from apoptotic cells form ICs with each autoantibody, and their ICs may become trapped at anionic sites in the glomerular basement membrane, leading to deposition in glomeruli. These autoantibodies may be useful for prediction of LN in subsets of SLE patients who are negative for anti-dsDNA antibodies.

Non-invasive imaging to monitor lupus nephritis and neuropsychiatric systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is an autoimmune disease that can affect multiple different organs, including the kidneys and central nervous system (CNS). Conventional radiological examinations in SLE patients include volumetric/ anatomical computed tomography (CT), magnetic resonance imaging (MRI) and ultrasound (US). The utility of these modalities is limited, however, due to the complexity of the disease. Furthermore, standard CT and MRI contrast agents are contraindicated in patients with renal impairment. Various radiologic methods are currently being developed to improve disease characterization in patients with SLE beyond simple anatomical endpoints. Physiological non-contrast MRI protocols have been developed to assess tissue oxygenation, glomerular filtration, renal perfusion, interstitial diffusion, and inflammation-driven fibrosis in lupus nephritis (LN) patients. For neurological symptoms, vessel size imaging (VSI, an MRI approach utilizing T2-relaxing iron oxide nanoparticles) has shown promise as a diagnostic tool. Molecular imaging probes (mostly for MRI and nuclear medicine imaging) have also been developed for diagnosing SLE with high sensitivity, and for monitoring disease activity. This paper reviews the challenges in evaluating disease activity in patients with LN and neuropsychiatric systemic lupus erythematosus (NPSLE). We describe novel MRI and positron-emission tomography (PET) molecular imaging protocols using targeted iron oxide nanoparticles and radioactive ligands, respectively, for detection of SLE-associated inflammation.

The association of serum anti-ribosomal P antibody with clinical and serological disorders in systemic lupus erythematosus: a systematic review and meta-analysis

Objective

Anti-ribosomal P (anti-P) antibody is a serological specific marker of systemic lupus erythematosus (SLE). The aim of this study is to investigate the association of this antibody with clinical and serological disorders in SLE.

Methods

All relevant literature was retrieved from PubMed, EMBASE, Web of Science and CNKI databases. The qualities of these studies were evaluated using a modified version of the Newcastle–Ottawa scale. The associations of anti-P antibody with clinical and serological disorders were determined by the pooled odds ratio (OR) and the confidence interval (CI) calculated using meta-analysis with the Mantel–Haenszel method.

Results

Sixteen cohort studies with 2355 patients were included in this study. Malar rash, oral ulcer and photosensitivity were strongly associated with serum anti-P antibody, with OR (95% CI) values of 2.05 (1.42–2.92), 1.49 (1.05–2.13) and 1.44 (1.08–1.91), respectively. Arthritis and renal involvement were not associated with anti-P antibody, whereas a high heterogeneity was observed due to ethnicity and publication bias, respectively. Neuropsychiatric SLE (NPSLE), hepatic involvement, anti-dsDNA, anti-Sm and anti-cardiolipin antibodies (aCL) were observed more frequently in anti-P positive patients than in negative patients. Studies on hepatic involvement showed a low precision with substantially broad CI (2.56–11.2). A high heterogeneity presented among studies on NPSLE, anti-Sm and aCL.

Conclusions

Anti-P antibody is significantly associated with malar rash, oral ulcer, photosensitivity and serum anti-dsDNA antibody, and potentially associated with NPSLE, hepatic damage, serum anti-Sm and aCL.

Serum antinucleosome-specific antibody as a marker of autoimmunity in children with autism

Background

Increasing evidence of autoimmune phenomena in some individuals with autism could represent the presence of altered or inappropriate immune responses in this disorder. The role of the nucleosome in the induction of antibody response in some autoimmune-mediated tissue damage may provide novel targets for treatment. Due to the paucity of studies investigating the frequency of systemic auto-antibodies in autism, we are the first to investigate the frequency of antinucleosome-specific antibodies in a group of autistic children.

Methods

Serum antinucleosome-specific antibodies were measured by ELISA in 60 autistic children, between the ages of 3 and 12 years, in comparison to 60 healthy children. Autistic severity was assessed using the Childhood Autism Rating Scale (CARS).

Results

Autistic children had significantly higher serum antinucleosome-specific antibodies than healthy children (P <0.001). The seropositivity of antinucleosome-specific antibodies was found in 46.7% of autistic children. Autistic children with a family history of autoimmunity (40%) had a significantly higher frequency of serum antinucleosome-specific antibodies (83.3%) than patients without such a history (22.2%, P <0.001).

Conclusions

Serum levels of antinucleosome-specific antibodies were increased in some autistic children. However, these data should be treated with caution until further investigations are performed with a larger subject population to determine whether these antibodies have a role in the induction of autoimmunity in a subgroup of autistic children. The role of immunotherapy in children with autism should be also studied.

The spectrum of anti-chromatin/nucleosome autoantibodies: independent and interdependent biomarkers of disease

Autoantibodies directed to chromatin components date back to the discovery of the LE cell and the LE cell phenomenon circa 1950, and subsequent evidence that major components of that reaction were chromatin components and histones in particular. Over time, immunoassays ranging from ELISA and line immunoassays to more modern bead-based assays incorporated histone and DNA mixtures, purified histones, and purified nucleosomes leading to a more thorough understanding of the genesis and pathogenetic relationships of antibodies to chromatin components in systemic lupus erythematosus and other autoimmune conditions. More recently, interest has focussed on other components of chromatin such as high mobility group (HMG) proteins both as targets of B cell responses and pro-inflammatory mediators. This review will focus on immunoassays that utilize chromatin components, their clinical relationships, and newer evidence implicating HMG proteins and DNA neutrophil extracellular traps (NETs) as important players in systemic autoimmune rheumatic diseases.

Anti-nucleosome autoantibodies as markers for autoimmune hepatitis and their correlation with disease activity

AIM

To assess the prevalence of autoantibodies against nucleosomes (anti-nucleosome Ab) in patients with autoimmune hepatitis (AIH), examine the correlation between anti-nucleosome Ab and disease activity, and evaluate the effectiveness of anti-nucleosome Ab in predicting relapse.

METHODS

We analyzed serum anti-nucleosome Ab levels in 38 patients with AIH by enzyme-linked immunosorbent assay, and assessed their correlation with clinical characteristics.

RESULTS

Anti-nucleosome Ab levels were significantly higher in AIH, but not in patients with chronic hepatitis B (n = 20) or chronic hepatitis C (n = 20), compared to healthy controls (n = 15). The positive prevalence of anti-nucleosome Ab was 71.1% in AIH. Anti-nucleosome Ab levels were significantly lower during remission compared to that during flares within the same patients with AIH. Total bilirubin levels were significantly higher in patients with anti-nucleosome Ab levels of 53.7 U/mL or more compared to those with less than 53.7 U/mL at disease onset. Analysis of the reduction in anti-nucleosome Ab by immunosuppressive therapy in 16 AIH patients revealed that age at disease onset was significantly lower and IgG levels and relapse rates were significantly higher in patients with a reduction rate of less than 35% compared to those with a reduction rate 35% or more. The International Autoimmune Hepatitis Group score and γ-globulin levels were also higher in patients with reduction rates of less than 35% (borderline significance).

CONCLUSION

Anti-nucleosome Ab in AIH patients may be useful markers not only for disease diagnosis, but also for activity assessment and relapse prediction.

Serum nitrated nucleosome levels in patients with systemic lupus erythematosus: a retrospective longitudinal cohort study

Introduction

Circulating nucleosomes released from apoptotic cells are important in the pathogenesis of systemic lupus erythematosus (SLE). Both nucleosomes and anti-nucleosome antibodies are deposited in inflamed tissues in patients with SLE. Active inflammation promotes nitration of tyrosine residues on serum proteins. Our hypothesis was that levels of nitrated nucleosomes would be elevated in patients with SLE and could be associated with disease activity. We therefore carried out a retrospective longitudinal study to investigate factors affecting levels of nitrated nucleosomes (NN) in patients with SLE.

Methods

A novel serum ELISA was developed to measure serum NN and modified to measure serum nitrated albumin (NA). Levels of both NN and NA were measured in 397 samples from 49 patients with SLE followed through periods of disease flare and remission for a mean of 89 months. Anti-nucleosome antibody (anti-nuc) levels were measured in the same samples. The effects of 24 different clinical, demographic and serological variables on NN, NA and anti-nuc levels were assessed by univariable and multivariable analysis.

Results

Patients with SLE had higher mean NN than healthy controls or patients with other autoimmune rheumatic diseases (P =0.01). Serum samples from 18 out of 49 (36.7%) of SLE patients were never positive for NN. This group of 18 patients was characterized by lower anti-double stranded DNA antibodies (anti-dsDNA), disease activity and use of immunosuppressants. In the remaining 63.3%, NN levels were variable. High NN was significantly associated with anti-Sm antibodies, vasculitis, immunosuppressants, hydroxychloroquine and age at diagnosis. NN levels were raised in neuropsychiatric flares. NN levels did not completely parallel NA results, thus providing additional information over measuring nitration status alone. NN levels were not associated with anti-nuc levels.

Conclusions

NN are raised in a subset of patients with SLE, particularly those who are anti-Sm positive. Elevated NN may be a marker of vascular activation and neuropsychiatric flares in these patients.

Cytokeratin-19 fragments, nucleosomes and neuron-specific enolase as early measures of chemotherapy response in non-small cell lung cancer

AIM

To investigate the reduction in the serum level of cytokeratin-19 fragments (CYFRA 21-1), nucleosomes and neuron-specific enolase (NSE) as early measures of the response to chemotherapy in non-small cell lung cancer (NSCLC).

METHODS

Forty-two consecutive patients with locally advanced NSCLC were included. All patients received platinum-based chemotherapy. Staging investigations and quantification of CYFRA 21-1, nucleosomes and NSE (using enzyme-linked immunosorbent assay, ELISA) were performed before the start of treatment and after the second cycle of chemotherapy. According to the response to chemotherapy, patients were classified into 3 groups: (I) disease regression, (II) stable disease, and (III) progressive disease. The reduction in the levels of tumor markers was correlated with the response to chemotherapy.

RESULTS

After the second cycle of chemotherapy, groups I and II had significantly decreased serum levels of CYFRA 21-1 (p<0.05). Similarly, the concentration of nucleosomes was significantly lower than the baseline levels in groups I (p=0.0008) and II (p=0.003). The reduction of both CYFRA 21-1 and nucleosome levels was not significant for patients in group III. In all groups the reduction of NSE levels in response to chemotherapy was not significant. As a marker of response to chemotherapy, CYFRA 21-1 showed the highest sensitivity (88.9%) and specificity (77.4%) compared with nucleosomes (77.8% and 58.1% respectively) and NSE (66.7% and 51.8% respectively).

CONCLUSION

The reduction in the serum level of CYFRA 21-1 and nucleosomes may be used for early identification of NSCLC patients with good response to chemotherapy.

Are anti-nucleosome antibodies a better diagnostic marker than anti-dsDNA antibodies for systemic lupus erythematosus? A systematic review and a study of metanalysis

BACKGROUND

Methods to detect anti-nucleosome antibodies (ANuA) have been available for more than 10 years and the test has demonstrated its good sensitivity and high specificity in diagnosing systemic lupus erythematosus (SLE). Despite these data produced through clinical and laboratory research, the test is little used.

OBJECTIVE

To verify the diagnostic performance of methods for measuring ANuA and to compare them with those for anti-dsDNA antibodies.

DATA SOURCES

A systematic review of English and non-English articles using MEDLINE and EMBASE with the search terms "nucleosome", "chromatin", "anti-nucleosome antibodies" and "anti-chromatin antibodies". Additional studies were identified checking reference lists in the selected articles.

STUDY SELECTION

We selected studies reporting on anti-nucleosome tests performed by quantitative immunoassays, on patients with SLE as the index disease (sensitivity) and a control group (specificity). A total of 610 titles were initially identified with the search strategy described. 548 publications were subsequently excluded based on abstract and title. Full-text review was undertaken as the next step on 62 publications providing data on anti-nucleosome testing; 25 articles were then excluded because they did not include either SLE patients or a control group, and 37 articles were selected for the metanalysis. Finally, a sub-metanalysis study was conducted on the 26 articles providing data on both ANuA and anti-dsDNA antibody assays in the same series of patients.

DATA EXTRACTION

Extraction of data from selected articles was performed by two authors independently, using predefined criteria: the number of patients with SLE as the index case, and the number of healthy or diseased controls; specification of the analytical method used to detect anti-nucleosome and anti-dsDNA antibodies; the cut-off used in the study; and the sensitivity and specificity of the assay. Demographic and clinical data on the population investigated (adults or children; lupus patients with or without nephritis; patients with active or inactive disease) were also recorded and analyzed in a separate evaluation.

RESULTS

The systematic review and metanalysis showed that the overall sensitivity of the ANuA assay is 61% (confidence interval-CI, 60-62) and the specificity 94% (CI, 94-95). The overall positive likelihood ratio is 13.81 (CI, 9.05-21.09) and the negative likelihood ratio 0.38 (CI, 0.33-0.44). The odds ratio for having SLE in ANuA-positive patients is 40.7. The comparative analysis on anti-dsDNA antibodies conducted on the 26 studies which provided data for both antibodies showed that ANuA have greater diagnostic sensitivity (59.9% vs 52.4%) and a specificity rating only slightly higher (94.9% vs 94.2%). The probability that a subject with positive ANuA have SLE is 41 times greater than a subject with negative ANuA, while for anti-dsDNA the probability is 28 times greater. These figures are even more impressive in children, in whom ANuA have an odds ratio for the diagnosis of SLE of 146, compared to 51 for anti-dsDNA antibodies. In selected studies, ANuA (p<0.0001) but not anti-dsDNA antibodies (p=0.256) were significantly associated with disease activity measured by the international score systems. However, neither antibody appears to correlate with kidney involvement.

CONCLUSIONS

Data from the metanalysis have shown that ANuA have equal specificity but higher sensitivity and prognostic value than anti-dsDNA antibodies in the diagnosis of SLE. Despite a certain heterogeneity among the various studies, the use of ANuA appears more efficacious than anti-dsDNA.

Lupus nephritis: role of antinucleosome autoantibodies

The discovery of autoantigen clustering in blebs at the surface of apoptotic cells boosted research on the role of apoptosis in systemic lupus erythematosus (SLE) and led to the discovery of autoantigen modification during apoptosis. Normally, apoptotic cells are cleared efficiently and swiftly. However, it became clear that in SLE insufficient removal of apoptotic material leads to the release of these modified autoantigens. This creates the danger that these modified autoantigens are recognized by the immune system. Indeed, dendritic cells, the professional antigen-presenting cells, phagocytose these modified autoantigens, which leads to maturation and induction of a proinflammatory state of these dendritic cells. As a consequence, they present these modified autoantigens to T cells in an immunogenic way, which become activated and stimulate autoreactive B cells to secrete autoantibodies. In this review the currently available evidence for the sequential steps in the pathogenesis of SLE is discussed. Furthermore, the mechanisms responsible for the nephritogenicity of antinucleosome antibodies are reviewed. This will reveal that nucleosomes are not only a major driving force in the formation of antinuclear antibodies, but also play a pivotal role in the development of tissue lesions by mediating binding of autoantibodies to basement membranes as exemplified for the kidney.

Antinucleosome antibodies as a potential biomarker for the evaluation of renal pathological activity in patients with proliferative lupus nephritis

The objective of this study is to evaluate the correlation between antinucleosome antibodies and renal pathological activity in patients with proliferative lupus nephritis (LN). We evaluated 36 patients with proliferative LN, 14 non-renal lupus patients and 10 healthy volunteers. Lupus activity was assessed using the British Isles Lupus Assessment Group 2004 (BILAG 2004) index, serum anti-double stranded DNA (anti-dsDNA) levels, serum complement levels and daily urinary protein levels. All 36 lupus nephritis patients received renal biopsy. Antinucleosome antibodies were detected by enzyme-linked immunosorbent assay (ELISA). Our results showed that levels of serum antinucleosome antibodies were significantly higher in LN patients (median 90.35 units/ml, interquartile range [IQR] 37.38–135.23) than in non-renal SLE patients (median 5.45 units/ml, IQR 2.6–28.93, p <0.05) and in healthy volunteers (median 3.35 units/ml, IQR 2.95–5.23, p <0.001). Serum levels of antinucleosome antibodies were positively correlated with BILAG index (Spearman’s r = 0.645, p <0.001) and serum anti-dsDNA antibody levels ( rs = 0.644, p <0.01), while serum levels of antinucleosome antibodies were negatively correlated with serum levels of C3 ( rs = -0.400, p <0.01) and C4 ( rs = -0.300, p <0.05). Serum levels of antinucleosome antibodies were positively correlated with the histological activity index of LN ( rs = 0.368, p <0.05). However, there was no significant correlation between serum levels of antinucleosome antibodies and the histological chronicity index. In conclusion, the serum level of antinucleosome antibodies is a potential biomarker for early recognition of renal involvement and evaluation of disease activity in SLE. Our preliminary results suggested that serum levels of antinucleosome antibodies might be a potential biomarker in evaluating pathological activity of LN.

Distinctive autoantibody profile in Mexican Mestizo systemic sclerosis patients

Systemic sclerosis (SSc) shows variable clinical expression among different ethnic groups. Herein, we describe the clinical features, prevalence of organ involvement, and autoantibody profile in Mexican Mestizo SSc patients and we compare them with patients from other ethnic groups.We included 139 SSc patients. They underwent clinical evaluation and were tested for antinuclear antibodies (ANA), anticentromere antibodies (ACA), anti-topoisomerase I, anti-RNA polymerase III, anti-U1 RNP, anti-U3 RNP, anti-U11/U12 RNP, anti-Th/To, anti-PM-Scl, anti-Ku, antinucleosome, anti-double-stranded DNA (dsDNA), anti-Sm, anti-SSA, and anti-SSB antibodies. Female predominance (93.5%) was noted; 56.8% of patients had limited cutaneous SSc; 91% had peripheral vascular involvement; 70% had joint involvement; 27% had musculoskeletal damage; 66% had gastrointestinal involvement; 41% had interstitial lung disease; 32% had pulmonary arterial hypertension (PAH); 11% had cardiac involvement; and in 1.4% renal involvement was observed. Our patients showed lower frequency of renal crisis and higher frequency of PAH than patients from other ethnic groups; also they showed higher frequency of ACA than Japanese and African American patients, higher frequency of anti-topoisomerase I than Caucasian and African American patients, higher frequency of anti-PM-Scl and anti-Ku and lower frequency of anti-RNA Pol III than the other ethnic groups. High frequencies of antinucleosome (41%) and anti-dsDNA (63%) were identified. SSc-specific autoantibody frequencies are different in our patients and in those from other ethnic groups; associations of autoantibodies with clinical manifestations are confirmed in our patients. Ethnicity and the interaction of gene and environmental factors may influence the clinical picture and autoantibody profile in SSc patients.

Anti-C1q antibodies have higher correlation with flares of lupus nephritis than other serum markers

OBJECTIVE

Autoantibodies are important in the diagnosis and classification of systemic lupus erythematosus (SLE), but whether they correlate with changes in disease activity within individual patients is controversial. We assessed the association between changes in SLE global and renal activity and changes in several autoantibodies and cell adhesion molecules in patients with SLE.

METHODS

Stored sera collected at two or three clinic visits from each of 49 SLE patients (91% female, 59% African-American, 31% Caucasian, 10% other ethnicity, 38% under 30 years, 41% between 30-44 years, and 21% 45-63 years) were analyzed. The visits were chosen to include one visit with proteinuria, and one or two without, for each patient. Global disease activity was measured by the Physician's Global Assessment (PGA), SELENA-SLEDAI (SLE Disease Activity Index modified to exclude anti-dsDNA and complement) and renal activity assessed by urine protein (by urine dipstick) and Renal Activity Score. Sera were assayed for anti-C1q, anti-chromatin, anti-dsDNA, anti-ribosomal P, monocyte chemotactic protein-1 (MCP-1), vascular cell adhesion molecule (VCAM) intercellular adhesion molecule (ICAM) and complement. The associations between changes in disease activity and changes in biomarker levels were assessed.

RESULTS

In terms of global disease activity, anti-C1q had the highest association with the PGA (p = 0.09) and was strongly associated with modified SELENA-SLEDAI (p = 0.009). In terms of renal activity, anti-C1q had the highest association with proteinuria (p = 0.079), and was strongly associated with Renal Activity Score (p = 0.006).

CONCLUSION

Anti-C1q performed the best of the potential biomarkers, being significantly associated with the modified SELENA-SLEDAI and with the Renal Activity Score. This study indicates the potential superior utility of anti-C1q over anti-dsDNA and other measures to track renal activity.

Impaired deoxyribonuclease I activity in patients with inflammatory bowel diseases

Background and Aims. Deoxyribonuclease I (DNaseI) is an endonuclease that facilitates chromatin breakdown and promotes susceptibility to autoimmune disorders. The aim of current study was to investigate serum DNase I activity in patients with inflammatory bowel diseases (IBD). Patients and Methods. A cohort of 110 IBD patients was evaluated, aged 35 ± 12 years, 77 with Crohn's disease (CD) and 33 with ulcerative colitis (UC). 50 SLE patients and 50 healthy blood donors were examined as control groups. Results. DNase I activity in IBD patients was significantly lower than in healthy individuals, but higher than in SLE patients (P < .0001). Patients with UC showed higher DNase I activity than CD patients, P = .21. DNase I activity in female patients with IBD was significantly lower than in males, P = .024; however, no differences in DNase I activity were found in relation to gender in healthy individuals. DNase I activity has shown a strong negative correlation with the serum concentration of anti-nucleosomal antibodies in the autoimmune (SLE + IBD) cohort, as well as in the separate IBD cohort. Conclusions. Reduced serum DNase I activity probably has pathogenetic consequences in IBD. Induction of autoantibodies towards nucleosomes could be a reflection of impaired DNase I activity.

Clearing the complexity: immune complexes and their treatment in lupus nephritis

Systemic lupus erythematosus (SLE) is a classic antibody-mediated systemic autoimmune disease characterised by the development of autoantibodies to ubiquitous self-antigens (such as antinuclear antibodies and antidouble-stranded DNA antibodies) and widespread deposition of immune complexes in affected tissues. Deposition of immune complexes in the kidney results in glomerular damage and occurs in all forms of lupus nephritis. The development of nephritis carries a poor prognosis and high risk of developing end-stage renal failure despite recent therapeutic advances. Here we review the role of DNA-anti-DNA immune complexes in the pathogenesis of lupus nephritis and possible new treatment strategies aimed at their control.

Performance of anti-C1q, antinucleosome, and anti-dsDNA antibodies for detecting concurrent disease activity of systemic lupus erythematosus

The objective of this study is to evaluate the specificity and sensitivity of antinucleosome, anti-C1q, and anti-dsDNA antibodies for detecting concurrent disease activity in systemic lupus erythematosus (SLE). Consecutive patients were recruited for serological testing of anti-dsDNA, IgG-antinucleosome, IgG-anti-C1q, and complement levels. SLE disease activity was assessed by SLEDAI and physician's global assessment (PGA). The levels of these antibodies, complements, and disease activity scores were correlated. The specificity and sensitivity of these antibodies in detecting SLE activity was determined. We recruited 245 SLE patients (95% women, age 40.6 ± 12.2 years). The prevalence of positive anti-dsDNA, antinucleosome and anti-C1q antibodies was 55%, 44%, and 21%, respectively. All 3 antibodies correlated significantly with SLEDAI and PGA scores but were correlated inversely with complement levels (P < 0.001 in all). Titers of anti-dsDNA and anti-C1q, but not antinucleosome, correlated significantly with the renal SLEDAI score. The sensitivity of anti-dsDNA, antinucleosome, and anti-C1q for detecting the presence of active renal disease was 75%, 47%, and 53%, respectively. Anti-C1q had the highest specificity for active lupus renal disease (84%) followed by antinucleosome (57%) and the anti-dsDNA antibody (49%). The negative predictive value (NPV) of a negative anti-dsDNA and anti-C1q for active renal disease was 91%. For concurrent extrarenal SLE activity, the specificity was also highest with anti-C1q (83%). We conclude that antinucleosome does not perform better than anti-dsDNA for detecting concurrent SLE activity. The anti-C1q antibody, however, is more specific than anti-dsDNA for both active renal and extrarenal lupus. The absence of both anti-dsDNA and anti-C1q has a high NPV for renal activity.

Contribution of IRF5 in B cells to the development of murine SLE-like disease through its transcriptional control of the IgG2a locus

Interferon regulatory factor (IRF) 5 is a key transcription factor for the activation of innate immune responses downstream of Toll-like receptor signaling. Based on recent genetic analyses, IRF5 is a focus for its potential involvement in systemic lupus erythematosus (SLE), although how IRF5 contributes to SLE is uncertain. In this study, we demonstrate a requirement for IRF5 in the development of murine SLE via its role in B lymphocytes. We show that antinuclear autoantibodies and Ig glomerular deposits, hallmarks of SLE, are absent in Irf5(-/-) mice challenged to develop SLE by pristane injection. In particular, production of autoantibodies of the IgG2a subtype, the most prominent isotype in inducing autoimmunity, requires IRF5. Finally, we provide evidence for the critical role of this transcription factor in the secretion of pathogenic antibodies through its direct control of class switch recombination of the gamma2a locus. By demonstrating a B-cell-intrinsic role, this study places IRF5 in a context that may have implications for understanding the pathogenesis of human SLE.

Biomarkers for lupus nephritis: a critical appraisal

Kidney disease is one of the most serious manifestations of systemic lupus erythematosus (SLE). Despite the improvement in the medical care of SLE in the past two decades, the prognosis of lupus nephritis remains unsatisfactory. Besides exploring more effective but less toxic treatment modalities that will further improve the remission rate, early detection and treatment of renal activity may spare patients from intensive immunosuppressive therapies and reduce renal damage. Conventional clinical parameters such as creatinine clearance, proteinuria, urine sediments, anti-dsDNA, and complement levels are not sensitive or specific enough for detecting ongoing disease activity in the lupus kidneys and early relapse of nephritis. Thus, novel biomarkers are necessary to enhance the diagnostic accuracy and sensitivity of lupus renal disease, prognostic stratification, monitoring of treatment response, and detection of early renal flares. This paper reviews promising biomarkers that have recently been evaluated in longitudinal studies of lupus nephritis.

Autoantibody-dependent and autoantibody-independent roles for B cells in systemic lupus erythematosus: past, present, and future

It has long been known that B cells produce autoantibodies and, thereby, contribute to the pathogenesis of many autoimmune diseases. Systemic lupus erythematosus (SLE), a prototypic systemic autoimmune disorder, is characterized by high-circulating autoantibody titers and immune-complex deposition that can trigger inflammatory damage in multiple organs/organ systems. Although the interest in B cells in SLE has historically focused on their autoantibody production, we now appreciate that B cells have multiple autoantibody-independent roles in SLE as well. B cells can efficiently present antigen and activate T cells, they can augment T cell activation through co-stimulatory interactions, and they can produce numerous cytokines which affect inflammation, lymphogenesis, and immune regulation. Not surprisingly, B cells have become attractive therapeutic targets in SLE. With these points in mind, this review will focus on the autoantibody-dependent and autoantibody-independent roles for B cells in SLE and on therapeutic approaches that target B cells.

Anti-nuscleosome antibody, a reliable indicator for lupus nephritis

Systemic lupus erythematosus (SLE) is characterized by the presence of antinuclear antibodies (ANA). ANAs are aimed against native DNA, as well as histone proteins and small nuclear ribonucleoproteins, also could be targeted against the entire chromatin, consisted of nucleosomes. Herein, we assessed the frequency and the concentration of anti-nucleosome antibodies (aNS) in a group of 107 Hungarian patients with SLE. Moreover, correlations between these autoantibody concentrations and disease activity, as well as organ manifestations, mainly renal symptoms were evaluated. The occurrence of positive aNS, anti-dsDNA and anti-histone (aH) antibodies were 39.2, 28.0 and 47.6%, respectively. All the three autoantibodies were represented with significantly higher titers in patients with lupus nephritis. A positive correlation was found between the concentration of these autoantibodies and disease activity. The long disease duration (mean 8.5 years) and consequent low disease activity (mean disease activity index: 3.28) could be the reason for the relatively low occurrence of ANAs amongst patients. Besides anti-dsDNA, the assessment of aNS and aH antibodies could be useful in the diagnosis and follow-up of SLE. The authors discuss the possible role of aNS autoantibodies in the pathogenesis of lupus nephritis.

Relationship between anti-dsDNA, anti-nucleosome and anti-alpha-actinin antibodies and markers of renal disease in patients with lupus nephritis: a prospective longitudinal study

Introduction

Glomerulonephritis is a major cause of morbidity and mortality in patients with systemic lupus erythematosus (SLE). Deposition of autoantibodies in the glomeruli plays a key role in the development of lupus nephritis (LN). Different groups have proposed that either anti-nucleosome antibodies or antibodies that bind the intrinsic renal antigen, α-actinin, are central to the pathogenesis of LN. These theories have been based mainly on cross-sectional studies in patients and on experiments in animal models. No previous longitudinal studies have compared the relationships between levels of these antibodies and markers of renal function. We assessed how well anti-α-actinin, anti-nucleosome and anti-double-stranded DNA (anti-dsDNA) antibodies reflected renal outcome measures in patients with new-onset LN followed for up to 2 years.

Methods

Renal disease activity was monitored by measuring urine protein/creatinine ratio (PCR), serum albumin and a composite outcome of renal remission. At each time point, anti-nucleosome and anti-α-actinin antibodies were measured by enzyme-linked immunosorbent assay. High-avidity anti-dsDNA antibodies were measured using the Farrzyme assay. We analysed relationships between levels of the three antibodies and between antibody levels and renal outcome measures over time.

Results

Levels of anti-nucleosome and anti-dsDNA were positively correlated with each other (r = 0.6, P = 0.0001) but neither correlated with anti-α-actinin level. At baseline, mean anti-nucleosome levels were higher in patients with LN than in healthy controls (0.32 versus 0.01, P < 0.001). The same was true for anti-dsDNA antibodies (0.50 versus 0.07, P < 0.001) but not for anti-α-actinin (0.33 versus 0.29). Over the follow-up period, anti-nucleosome and anti-dsDNA levels associated positively with urine PCR (P = 0.041 and 0.051, respectively) and negatively with serum albumin (P = 0.027 and 0.032, respectively). Both anti-nucleosome and anti-dsDNA levels were significantly lower during renal remission than when renal disease was active (P = 0.002 and 0.003, respectively). However, there was no relationship between anti-α-actinin levels and urine PCR, serum albumin or remission status.

Conclusions

This prospective longitudinal clinical study is the first to compare levels of anti-nucleosome, anti-dsDNA and anti-α-actinin antibodies in the same patients with SLE. Our results support the concept that, in the majority of patients, anti-nucleosome antibodies play a major role in pathogenesis of LN, in contrast to anti-α-actinin antibodies.

[Systemic lupus erythematosus. Target criteria for treatment]

Systemic lupus erythematosus (SLE) is a chronic systemic intermittent autoimmune disease, which can affect nearly all organ systems. The disease is characterized by the detection of more than 100 different auto-antibodies. For the clinical practice as well as in controlled clinical studies it is absolutely necessary to define target criteria which allow the evaluation of the effectiveness of therapy. Many instruments are available for measuring the activity of the disease, the quality of life, the extent of irreversible damage and the individual manifestation in organs. There are also now various biomarkers to characterize the pathophysiologic aspects, clinical activity, therapeutic effectiveness and prognosis.

A broad screen for targets of immune complexes decorating arthritic joints highlights deposition of nucleosomes in rheumatoid arthritis

Deposits of Ig and complement are abundant in affected joints of patients with rheumatoid arthritis (RA) and in animal models of RA in which antibodies are demonstrably pathogenic. To identify molecular targets of the Igs deposited in arthritic joints, which may activate local inflammation, we used a combination of mass spectrometry (MS) and protein microarrays. Immune complexes were affinity-purified from surgically removed joint tissues of 26 RA and osteoarthritis (OA) patients. Proteins complexed with IgG were identified by proteomic analysis using tandem MS. A striking diversity of components of the extracellular matrix, and some intracellular components, copurified specifically with IgG from RA and OA tissues. A smaller set of autoantigens was observed only in RA eluates. In complementary experiments, IgG fractions purified from joint immune complexes were tested on protein microarrays against a range of candidate autoantigens. These Igs bound a diverse subset of proteins and peptides from synovium and cartilage, different from that bound by normal serum Ig. One type of intracellular protein detected specifically in RA joints (histones H2A/B) was validated by immunohistology and found to be deposited on the cartilage surface of RA but not OA joints. Thus, autoantibodies to many determinants (whether deposited as "neoantigens" or normal constituents of the extracellular matrix) have the potential to contribute to arthritic inflammation.