Nucleosomes in the pathogenesis of systemic lupus erythematosus

Circulating nucleosomes as potential biomarkers for cancer diagnosis and treatment monitoring

Nucleosomes play a crucial role in regulating gene expression through their composition and post-translational modifications. When cells die, intracellular endonucleases are activated and cleave chromatin into oligo- and mono-nucleosomes, which are then released into the body fluids. Studies have shown that the levels of nucleosomes are increased in serum and plasma in various cancer types, suggesting that analysis of circulating nucleosomes can provide an initial assessment of carcinogenesis. However, it should be noted that elevated serum nucleosome levels may not accurately diagnose certain tumor types, as increased cell death may occur in different pathological conditions. Nevertheless, detection of circulating nucleosomes and their histone modifications, along with specific tumor markers, can help diagnose certain types of cancer. Furthermore, monitoring changes in circulating nucleosome levels during chemotherapy or radiotherapy in patients with malignancies can provide valuable insights into clinical outcomes and therapeutic efficacy. The utilization of circulating nucleosomes as biomarkers is an exciting and emerging area of research, with the potential for early detection of various diseases and monitoring of treatment response. Integrating nucleosome-based biomarkers with existing ones may improve the specificity and sensitivity of current assays, offering the possibility of personalized precision medical treatment for patients.

Autoantibodies in lupus nephritis useful in distinguishing proliferative nephritis from membranous nephritis

OBJECTIVES

This study was conducted to determine autoantibodies associated with lupus nephritis (LN), especially those useful in diagnosing proliferative and membranous nephritis.

METHODS

A total of 106 patients with LN and 63 patients with systemic lupus erythematosus but no nephritis were enrolled; then, 55 patients were selected from the LN group and were divided into two groups: proliferative nephritis patients (n = 36) and membranous nephritis patients (n = 19). The autoantibody profiles of patients' sera were evaluated using the EUROLINE ANA Profile 3 (IgG) kit.

RESULTS

A higher positivity rate of anti-double-stranded DNA antibody and anti-histone antibody was seen in LN patients compared to nonrenal systemic lupus erythematosus patients. In comparing between proliferative and membranous nephritis, the positivity of anti-nucleosome antibody was higher in proliferative nephritis, although it was not statistically significant. However, anti-nucleosome antibody-positive patients with LN had a higher prevalence of haematuria and pyuria, which are strong indications of proliferative nephritis. Also, a significantly higher positivity rate of anti-RNP70 antibody was seen in membranous nephritis compared to proliferative nephritis.

CONCLUSIONS

Our results showed that anti-nucleosome and anti-RNP70 antibodies may be predictive nonhistological factors for discriminating between proliferative and membranous LN.

The Formation of Melanocyte Apoptotic Bodies in Vitiligo and the Relocation of Vitiligo Autoantigens under Oxidative Stress

Background

Oxidative stress has a vital role in the early stages of vitiligo. Autoantigens released from apoptotic melanocytes (MC) under oxidative stress are involved in the presentation and recognition of antigens. However, the transport of autoantigens to the cell surface and their release to the extracellular environment are still unclear. Apoptotic bodies (ABs) have always been considered as a key source of immunomodulators and autoantigens. Yet, the role of ABs in the immune mechanism of vitiligo is still unknown.

Purpose

To explore whether MC's autoantigens translocate into ABs during oxidative stress-induced apoptosis and study the molecular mechanisms underlying autoantigen migration and AB formation.

Methods

PIG3V (an immortalized human vitiligo melanocyte cell line) were treated with H₂O₂, and ABs were separated. Transmission electron microscopy, flow cytometry, Western blot, mass spectrometry, and other methods were used to determine the relocation of specific antigens in PIG3V cells to ABs. After pretreatment with specific inhibitors (Rho kinase (Y-27632), myosin light chain kinase (MLCK, ML-9), pan-caspase (zVAD-FMK), and JNK (SP600125)), the pathway of autoantigen translocation into ABs and the formation of apoptotic bodies were determined.

Results

When treated with 0.8 mM H₂O₂, ABs were released from these cells. Autoantigens such as tyrosinase-related protein 1 (TYRP-1) and cleavage nuclear membrane antigen Lamin A/C (Asp230) were concentrated in ABs. The expression of autoantigens and the formation of ABs increased in a time- and dose-dependent manner after treatment with H₂O₂, while the application of specific inhibitors inhibited the formation of apoptotic bodies, i.e., the expression of antigens.

Conclusion

Vitiligo autoantigens translocate into ABs in the process of apoptosis induced by oxidative stress. The cytoskeletal protein activation pathway and the JNK-related apoptosis pathway are involved in the transport of autoantigens and the formation of ABs. ABs may be the key bridge between MC cell apoptosis and cellular immunity.

An Update on the Pathogenesis of Skin Damage in Lupus

PURPOSE OF REVIEW

Lupus erythematosus (LE) is characterized by broad and varied clinical forms ranging from a localized skin lesion to a life-threatening form with severe systemic manifestations. The overlapping between cutaneous LE (CLE) and systemic LE (SLE) brings difficulties to physicians for early accurate diagnosis and sometimes may lead to delayed treatment for patients. We comprehensively review recent progress about the similarities and differences of the main three subsets of LE in pathogenesis and immunological mechanisms, with a particular focus on the skin damage.

RECENT FINDINGS

Recent studies on the mechanisms contributing to the skin damage in lupus have shown a close association of abnormal circulating inflammatory cells and abundant production of IgG autoantibodies with the skin damage of SLE, whereas few evidences if serum autoantibodies and circulating inflammatory cells are involved in the pathogenesis of CLE, especially for the discoid LE (DLE). Till now, the pathogenesis and molecular/cellular mechanism for the progress from CLE to SLE are far from clear. But more and more factors correlated with the differences among the subsets of LE and progression from CLE to SLE have been found, such as the mutation of IRF5, IFN regulatory factors and abnormalities of plasmacytoid dendritic cells (PDCs), Th1 cells, and B cells, which could be the potential biomarkers for the interventions in the development of LE. A further understanding in pathogenesis and immunological mechanisms for skin damage in different subsets of LE makes us think more about the differences and cross-links in the pathogenic mechanism of CLE and SLE, which will shed a light in predictive biomarkers and therapies in LE.

Serum/plasma homocysteine levels in patients with systemic lupus erythematosus: a systematic review and meta-analysis

Published studies have shown contradictory results in the association of serum/plasma levels of homocysteine (HCY) with systemic lupus erythematosus (SLE). This study is to systematically evaluate the association of serum/plasma HCY levels in SLE. A search was done using PubMed, Embase, Web of Science, and ScienceDirect databases up to 7 April 2019. Thirty-six articles including 2919 SLE patients and 3120 healthy controls were finally included in this meta-analysis. The HCY levels were significantly higher in SLE patients than in healthy controls (P < 0.001). The subgroup analysis revealed that Asian, African, Arab, Mixed, White and others as well as ages (< 35 and ≥ 35) had significant higher HCY levels in SLE patients than in the healthy controls. The study indicated that patients with disease activity index scores < 8 (P < 0.001) and ≥ 8 (P = 0.003) of SLE had significant higher HCY levels as compared with the healthy controls. It was also revealed that disease duration in SLE patients for < 10 and ≥ 10 years (P < 0.001) had significant higher HCY levels as compared with the healthy controls. A significant higher HCY level for body mass index (< 23 and ≥ 23) was found as well as measurement type in SLE patients than healthy controls. This meta-analysis demonstrated higher HCY levels in patients with SLE than healthy controls, suggesting a possible role of HCY in the disease.Key Points• Homocysteine (HCY) is closely related to the mechanisms of systemic lupus erythematosus (SLE).• This study reveals a significant correlation between HCY levels and the various indexes of disease activity.• This study reveals that medication may influence HCY levels in SLE.• This study also discovers that the subgroup analysis of all the factors influences the HCY levels in SLE patients.

Genome-Wide DNA Methylation Analysis of Chinese Patients with Systemic Lupus Erythematosus Identified Hypomethylation in Genes Related to the Type I Interferon Pathway

Background

Epigenetic variants have been shown in recent studies to be important contributors to the pathogenesis of systemic lupus erythematosus (SLE). Here, we report a 2-step study of discovery followed by replication to identify DNA methylation alterations associated with SLE in a Chinese population. Using a genome-wide DNA methylation microarray, the Illumina Infinium HumanMethylation450 BeadChip, we compared the methylation levels of CpG sites in DNA extracted from white blood cells from 12 female Chinese SLE patients and 10 healthy female controls.

Results

We identified 36 CpG sites with differential loss of DNA methylation and 8 CpG sites with differential gain of DNA methylation, representing 25 genes and 7 genes, respectively. Surprisingly, 42% of the hypomethylated CpG sites were located in CpG shores, which indicated the functional importance of the loss of DNA methylation. Microarray results were replicated in another cohort of 100 SLE patients and 100 healthy controls by performing bisulfite pyrosequencing of four hypomethylated genes, MX1, IFI44L, NLRC5 and PLSCR1. In addition, loss of DNA methylation in these genes was associated with an increase in mRNA expression. Gene ontology analysis revealed that the hypomethylated genes identified in the microarray study were overrepresented in the type I interferon pathway, which has long been implicated in the pathogenesis of SLE.

Conclusion

Our epigenetic findings further support the importance of the type I interferon pathway in SLE pathogenesis. Moreover, we showed that the DNA methylation signatures of SLE can be defined in unfractionated white blood cells.

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.

Autoantibodies in lupus nephritis patients requiring renal transplantation

The goal of this nested case-control study was to compare autoantibody profiles in systemic lupus erythematosus (SLE) patients with lupus nephritis (LN), lupus nephritis patients requiring renal transplantation (LNTP) and a SLE control group without nephritis (CON). Sera were assayed for a variety of autoantibodies by addressable laser bead immunoassay (ALBIA) and enzyme-linked immunoassay (ELISA) and to dsDNA by Crithidia luciliae assay. The frequency of nucleosome autoantibodies was significantly greater in the LNTP group (79%) compared to the LN (18%) and CON (9%) groups ( P < 0.0005). The frequency of other autoantibodies, including anti-dsDNA, did not differ significantly between groups. Among patients with LN, the odds of progressing to renal transplantation was 16-fold higher (OR 16.5 [95% CI 2.5, 125.7], P = 0.0005) in patients testing positive for anti-nucleosome antibodies compared to those who tested negative. Furthermore, the level of anti-nucleosome antibodies was significantly ( P < 0.00005) higher in the LNTP group (3.69 ± 2.79) than the LN (0.51 ± 0.51) and CON (0.34 ± 0.44) groups. Review of 48 renal biopsies from 29 patients indicated that there was no difference in renal histological classification among patients with anti-nucleosome antibodies compared to those who tested negative. Our observations suggest that nucleosome autoantibodies are a biomarker for more severe SLE renal disease requiring transplantation. Lupus (2007) 16, 394—400.

Circulating nucleosomes are associated with mortality in pediatric acute respiratory distress syndrome

Mechanisms underlying pediatric acute respiratory distress syndrome (PARDS) are poorly understood. The recent implication of circulating nucleosomes as pathogenic in sepsis and trauma-associated ARDS in adults led us to investigate the significance of nucleosomes in PARDS. We conducted a prospective, observational study on children with PARDS at the Children's Hospital of Philadelphia between July 2014 and September 2015. Plasma was collected within 48 h of PARDS onset and nucleosomes quantified by enzyme-linked immunosorbent assay. Samples from 76 children with PARDS (11 deaths, 14%) were collected early [median 15 (IQR 7, 21) h] after PARDS onset. Nucleosome levels were higher in nonsurvivors [0.59 AU (IQR 0.46, 0.84)] relative to survivors [0.21 AU (IQR 0.08, 0.33), rank sum P < 0.001]. Nucleosome levels were not associated with either Berlin (P = 0.845) or PALICC (P = 0.886) oxygenation categories, nor with etiology of PARDS (P = 0.527). Nucleosomes were correlated with increasing numbers of nonpulmonary organ failures (P = 0.009 for trend), and were higher in patients whose PaO2 /FiO2 worsened (P = 0.012) over the first 72 h of PARDS. In regression analysis, nucleosome levels were independently associated with mortality after adjusting for either age, severity of illness score, number of nonpulmonary organ failures, vasopressor score, or PaO2 /FiO2 (all P < 0.05). In conclusion, plasma nucleosome levels in early PARDS were associated with increased mortality, correlated with number of nonpulmonary organ failures, and preceded worsening oxygenation. The potential utility of this biomarker for prognostication, risk stratification, and mechanistic insight should be investigated further.

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.

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.

Biomarkers in systemic lupus erythematosus: challenges and prospects for the future

The search for lupus biomarkers to diagnose, monitor, stratify, and predict individual response to therapy is currently more intense than ever before. This effort is essential for several reasons. First, epidemic overdiagnosis and underdiagnosis of lupus, even by certified rheumatologists, leads to errors in therapy with concomitant side effects which may be more serious than the disease itself. Second, identification of lupus flares remains as much an art as it is a science. Third, the capacity to stratify patients so as to predict those who will develop specific patterns of organ involvement is not currently possible but would potentially lead to preventive therapeutic strategies. Fourth, only one new drug for the treatment of lupus has been approved by the US Food and Drug Administration in over 50 years. A major obstacle in this pipeline is the dearth of biomarkers available to prove a patient has responded to an experimental therapeutic intervention. This review will summarize the challenges faced in the discovery and validation of lupus biomarkers, the most promising lupus biomarkers identified to date, and the promise of future directions.

Circulating nucleosomes and biomarkers of immunogenic cell death as predictive and prognostic markers in cancer patients undergoing cytotoxic therapy

INTRODUCTION

Immunogenic cell death markers are released from apoptotic and necrotic cells upon pathologic or therapeutic causes and stimulate the innate and adaptive immune system. Cell death products such as nucleosomes, damage-associated molecular pattern (DAMP) molecules such as the high-mobility group box 1 protein (HMGB1) and its receptor of advanced glycation end products (sRAGE) are supposed to play an essential role in driving this process. However, this immunogenic activation may have dual effects, either by sensitizing the immune system for more efficient tumor cell removal or by creating a favorable tumor microenvironment that facilitates tumor growth, proliferation and invasiveness.

AREAS COVERED

Here, we review recent findings on the relevance of serum nucleosomes, DNAse activity, HMGB1 and sRAGE as biomarkers for the diagnosis, prognosis and therapy prediction in cancer disease.

EXPERT OPINION

In comparison with healthy controls, cancer patients demonstrated elevated serum levels of nucleosomes and HMGB1 while sRAGE levels were decreased. During locoregional and systemic cytotoxic therapies, a high release of nucleosomes and HMGB1 as well as low release of sRAGE before and during the initial phase of the treatment was found to be associated with poor response to the therapy and patient survival. Therefore, immunogenic cell death markers are promising tools for the prognosis, therapy prediction and monitoring in cancer patients.

Emerging and critical issues in the pathogenesis of lupus

Systemic lupus erythematosus (SLE) is a multisystemic, autoimmune disease, encompassing either mild or severe manifestations. SLE was originally labeled as being an immune complex-mediated disease, but further knowledge suggested its pathogenesis is motlier than that, involving complex interactions between predisposed individuals and their environment. People affected with SLE have their immune system skewed toward aberrant self-recognition usually after encountering a triggering agent. Defeats in early and late immune checkpoints contribute to tolerance breakdown and further generation and expansion of autoreactive cell-clones. B and T cells play a master role in SLE, however clues are emerging about other cell types and new light is being shed on SLE autoantibodies, since some of them display really harmful potential (pathogenic antibodies), while others are just connected with disease development (pathological antibodies) and may even be protective. Autoantibody generation is elicited by abnormal apoptosis and inefficient clearance of cellular debris causing intracellular autoantigens (e.g. nucleosomes) to persist in the extracellular environment, being further recognized by autoreactive cells. Here we explore the complexity of SLE pathogenesis through five core issues, i.e. genetic predisposition, B and T cell abnormalities, abnormal autoantigen availability, autoantibody generation and organ damage, relying on current knowledge and recent insights into SLE development.

Epigenetics and autoimmune diseases

Epigenetics is defined as the study of all inheritable and potentially reversible changes in genome function that do not alter the nucleotide sequence within the DNA. Epigenetic mechanisms such as DNA methylation, histone modification, nucleosome positioning, and microRNAs (miRNAs) are essential to carry out key functions in the regulation of gene expression. Therefore, the epigenetic mechanisms are a window to understanding the possible mechanisms involved in the pathogenesis of complex diseases such as autoimmune diseases. It is noteworthy that autoimmune diseases do not have the same epidemiology, pathology, or symptoms but do have a common origin that can be explained by the sharing of immunogenetic mechanisms. Currently, epigenetic research is looking for disruption in one or more epigenetic mechanisms to provide new insights into autoimmune diseases. The identification of cell-specific targets of epigenetic deregulation will serve us as clinical markers for diagnosis, disease progression, and therapy approaches.

Circulating apoptotic and necrotic cell death markers in patients with acute liver injury

BACKGROUND

The host response to cell death underpins the immune activation that follows acute liver injury, and measurement of circulating cell death markers could therefore aid prognostication following paracetamol overdose. Nucleosomes, formed during apoptosis, can complex with high-mobility group box 1 (HMGB1) protein and may play a pathogenic role in liver injury.

AIMS

To explore the levels and prognostic significance of nucleosomes, HMGB1, and other cell death markers following acute liver injury.

METHODS

Levels of plasma nucleosomes, HMGB1, caspase-cleaved cytokeratin-18 (M30) and total cytokeratin-18 (M65) were measured by immunoassay, in a cohort of 33 patients with paracetamol- and non-paracetamol-induced acute liver injury.

RESULTS

Admission nucleosome levels in paracetamol overdose patients were significantly higher than in chronic liver disease and healthy control subjects, but were similar in paracetamol and non-paracetamol patients (P=0.11). Nucleosome levels were not associated with death or requirement for liver transplantation, fulfillment of poor prognostic criteria or organ failure in paracetamol patients. Nucleosome levels correlated with levels of HMGB1 (r=0.500, P=0.009), alanine aminotransferase (r=0.410, P=0.038) and M65 (r=0.709, P<0.001), but not with M30 (r=0.309, P=0.124). None of the cell death markers analysed improved prognostication in paracetamol patients beyond the King's College criteria.

CONCLUSIONS

Plasma nucleosomes are significantly elevated following acute liver injury. Neither apoptotic nor necrotic cell death markers accurately predict survival following paracetamol-induced hepatotoxicity, suggesting that the extent and type of cell death play a limited role in determining outcome.

Proteomic characterization of thymocyte-derived microvesicles and apoptotic bodies in BALB/c mice

Several studies have characterized exosomes derived from different cell sources. In this work we set the goal of proteomic characterization of two less studied populations of membrane vesicles, microvesicles (100-800 nm) and apoptotic bodies (> 800 nm) released by thymus cells of BALB/c mice. The vesicles were isolated by the combination of differential centrifugation and gravity driven multistep filtration of the supernatant of thymus cell cultures. The size distribution of vesicle preparations was determined by transmission electron microscopy. Proteins were released from the vesicles, digested in solution, and analyzed using nano-HPLC/MS(MS). Ingenuity pathway analysis was used to identify functions related to membrane vesicle proteins. In apoptotic bodies and microvesicles we have identified 142 and 195 proteins, respectively. A striking overlap was detected between the proteomic compositions of the two subcellular structures as 108 proteins were detected in both preparations. Identified proteins included autoantigens implicated in human autoimmune diseases, key regulators of T-cell activation, molecules involved in known immune functions or in leukocyte rolling and transendothelial transmigration. The presence and abundance of proteins with high immunological relevance within thymocyte-derived apoptotic bodies and microvesicles raise the possibility that these subcellular structures may substantially modulate T-cell maturation processes within the thymus.

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.

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.

Serum BLC/CXCL13 concentrations and renal expression of CXCL13/CXCR5 in patients with systemic lupus erythematosus and lupus nephritis

OBJECTIVE

Systemic lupus erythematosus (SLE) is a prototype of systemic autoimmune disease in which cytokines such as B lymphocyte chemoattractant (BLC, or CXC motif ligand 13, CXCL13) may play important roles in pathogenesis. We investigated the implications of CXCL13 in SLE and lupus nephritis.

METHODS

Serum samples from 425 patients with SLE and 106 healthy control individuals were analyzed for the concentration of CXCL13 by ELISA. Tissue expression of CXCL13 and its corresponding receptor CXCR5 were observed in lupus kidney. The CXCR5-bearing B cells in SLE patients were analyzed by flow cytometry.

RESULTS

Serum levels of CXCL13 were higher in SLE patients compared to controls. SLE patients with lupus nephritis or positive anti-dsDNA antibodies had significantly higher serum CXCL13 levels. The peripheral venous blood B cells that bear CXCR5 were more abundant in SLE patients as detected by flow cytometry. CXCR5 and CXCL13 were highly expressed in the renal cortex from patients with lupus nephritis.

CONCLUSIONS

Our results suggest that BLC/CXCL13 as well as its corresponding receptor, CXCR5, may play important roles in the pathogenesis of SLE and in lupus nephritis.

Binding of circulating SLE autoantibodies to oxygen free radical damaged chromatin

Systemic lupus erythematosus (SLE) is a multisystem autoimmune disease characterized by various immunologic disorders, including production of autoantibodies, formation of immune complexes, decreased serum complement levels, and lymphocytopenia. One of the hallmarks of this disease is the loss of tolerance to nuclear antigens. The dominant presence of antibodies against the exposed conformational epitopes on chromatin strongly suggests that the pathogenic immune response in lupus is driven by chromatin. In the present study, the binding of SLE autoantibodies with native chromatin and oxygen free radical damaged chromatin was studied. As assessed by direct binding and inhibition ELISA, circulating SLE autoantibodies exhibited a high degree of specificity towards the reactive oxygen species (ROS)-modified chromatin in comparison to native chromatin and this binding specificity was reiterated visually by gel retardation assay. The data suggested possible role of modified chromatin in the induction of SLE autoantibodies and higher recognition of oxidatively damaged chromatin by antibodies in sera of SLE patients. It is indicated that free radical modified chromatin or nucleosomes might be the antigen for the production of circulating autoantibodies in SLE.

Immunotherapeutic applications of CpG oligodeoxynucleotide TLR9 agonists

Toll-like receptor 9 (TLR9) agonists have demonstrated substantial potential as vaccine adjuvants, and as mono- or combination therapies for the treatment of cancer and infectious and allergic diseases. Commonly referred to as CpG oligodeoxynucleotides (ODN), TLR9 agonists directly induce the activation and maturation of plasmacytoid dendritic cells and enhance differentiation of B cells into antibody-secreting plasma cells. Preclinical and early clinical data support the use of TLR9 agonists as vaccine adjuvants, where they can enhance both the humoral and cellular responses to diverse antigens. In mouse tumor models TLR9 agonists have shown activity not only as monotherapy, but also in combination with multiple other therapies including vaccines, antibodies, cellular therapies, other immunotherapies, antiangiogenic agents, radiotherapy, cryotherapy, and some chemotherapies. Phase I and II clinical trials have indicated that these agents have antitumor activity as single agents and enhance the development of antitumor T-cell responses when used as therapeutic vaccine adjuvants. CpG ODN have shown benefit in multiple rodent and primate models of asthma and other allergic diseases, with encouraging results in some early human clinical trials. Although their potential clinical contributions are enormous, the safety and efficacy of these TLR9 agonists in humans remain to be determined.

Clinical use of circulating nucleosomes

Nucleosomes, complexes of DNA and histone proteins, are released from dying and stressed cells into the blood circulation. Concentrations of circulating nucleosomes in plasma and serum are frequently found to be elevated in various cancers, and also in such acute conditions as stroke, trauma, and sepsis as well as in autoimmune diseases. The first part of this review focuses on the structural and functional properties of nucleosomes, the potential sources of nucleosome release into the circulation, the metabolism of circulating nucleosomes, and their pathophysiological role in disease. It goes on to describe the relevance of circulating nucleosomes in the diagnosis and prognosis of non-malignant conditions such as sepsis, stroke, and autoimmune disease. Finally, it describes the clinical value of nucleosomes in the diagnosis, staging, prognosis, and monitoring of therapy in cancer; in particular, their potential as a new diagnostic tool for the early estimation of response to cytotoxic cancer therapy is emphasized.

Analysis of ERCC2/XPD functional polymorphisms in systemic lupus erythematosus

Sunlight/ultraviolet (UV) irradiation has been recognized as an important risk factor for developing systemic lupus erythematosus (SLE). However, the interpretation of genetic variations involved in UV-light sensitivity is largely unknown. Recent studies indicated that two genetic variations of ERCC2/XPD gene (rs1799793 in exon 10 and rs13181 in exon 23) have been found to exert negative influences on nucleotide excision repair system. To analyse the possible contribution of the ERCC2/XPD functional single nucleotide polymorphisms in genetic susceptibility to SLE, the rs13181 and rs1799793 SNPs in ERCC2/XPD were genotyped by polymerase chain reaction followed by restriction fragment length polymorphism analysis. Association was studied by case-control analyses using samples from 172 SLE patients and 160 healthy controls. Haplotype analysis was performed to detect the association with genetic predisposition to SLE and the clinical features. Although these two functional genetic variations are linked to several immune dysfunction-induced diseases, no statistically significant differences in allele or genotype frequencies were observed between SLE patients and controls. Haplotype analysis showed that none of ERCC2/XPD haplotypes was associated with the incidence of SLE disease, nor the preference of clinical features. In conclusion, the ERCC2/XPD functional polymorphisms analysed in this study showed no association in genetic susceptibility to SLE.

Clinical relevance of circulating nucleosomes in cancer

Nucleosomes, complexes of DNA and histone proteins, are released during cell death into the blood circulation. Elevated serum and plasma levels have been found in various forms of cancer, but also in autoimmune diseases and acute situations such as stroke, trauma, and during sepsis. Here, the clinical relevance of circulating nucleosomes for diagnosis, staging, prognosis, and therapeutic monitoring of cancer is reviewed. Several studies have shown that levels of nucleosomes are significantly higher in serum and plasma of cancer patients in comparison to healthy controls. However, because of elevations of nucleosome levels in patients with benign diseases relevant for differential diagnosis, they are not suitable for cancer diagnosis. Concerning tumor staging, nucleosome levels correlate with tumor stage and presence of metastases in gastrointestinal cancer, but not in other tumor types. Prognostic value of circulating nucleosomes is found in lung cancer in univariate analyses, but not in multivariate analyses. Circulating nucleosomes are most informative for the monitoring of cytotoxic therapy. Strongly decreasing levels are mainly found in patients with remission of disease, whereas constantly high or increasing values are associated with progressive disease during chemo- and radiotherapy. In addition, therapy outcome is already indicated by the nucleosomal course during the first week of chemo- and radiotherapy in patients with lung, pancreatic, and colorectal cancer as well as in hematologic malignancies. Despite their non-tumor-specificity, kinetics of nucleosomes are valuable markers for the early estimation of therapeutic efficacy and may be helpful to adapting early cancer therapy in the future.

Pathogenic anti-nucleosome antibodies

There is increasing evidence that in systemic lupus erythematosus, nucleosomes, the basic chromatin component, represent both a driving immunogen and a major in vivo target for antibodies. Either a disturbed apoptosis or a reduced clearance of apoptotic cells by phagocytes may lead to an increased exposure of apoptotic nucleosomes to the immune system. These nucleosomes, which have been cleaved and modified during the process of apoptosis, escape normal clearance and encompass epitopes that normally are not encountered by the immune system. This may then lead to tolerance breaking and autoimmunity by the activation of nucleosome-specific autoreactive T cells (that help B cells) and subsequently to the production of anti-nucleosome, anti-histone and anti-DNA autoantibodies. Some anti-nucleosome antibody subsets are pathogenic and are involved in the nephritogenic process in systemic lupus erythematosus. Accordingly, several studies reported: (i) increased plasma circulating nucleosomes that positively correlated with an active disease, (ii) nucleosomes in typical glomerular deposits as well as in the basement membrane of non-lesional skin of systemic lupus erythematosus patients and (iii) a close correlation between nephritis and the presence of anti-nucleosome antibodies. Recent studies reported anti-nucleosome antibodies also in primary anti-phospholipid syndrome and particularly in patients with associated lupus-like disease.

Anti-chromatin (anti-nucleosome) antibodies: diagnostic and clinical value

Anti-chromatin (nucleosome) autoantibodies were one of the first autoantibodies ever detected since they make up the majority of antibodies causing LE Cell formation. The prevalence of anti-chromatin antibodies in systemic lupus erythematosus (SLE) varies from 50% to 100%, being similar to that of the classical positive LE cell. The presence of these antibodies can be used, in conjunction with clinical findings and other laboratory tests, to help in the diagnosis of SLE and drug-induced lupus. Anti-chromatin antibodies have also been found in a lesser percentage of other autoimmune disorders such as primary Sjögren's syndrome and primary antiphospholipid syndrome. The presence of anti-chromatin antibodies has also been linked to glomerulonephritis and disease activity in SLE patients. Recent studies demonstrated the induction of anti-chromatin (anti-nucleosome) antibodies after an anti-tumour necrosis factor (TNF)-alpha agent treatment.

A Central Role of Nucleosomes in Lupus Nephritis

Lupus nephritis is characterized by the presence of subendothelial and subepithelial immune complexes and thickening of the glomerular basement membranes (GBM). Electron-dense structures (EDS) in mesangium and GBM have been demonstrated to constitute target structures for nephritogenic autoantibodies in vivo. Whether these antibodies bind nucleosomal antigens within the EDS or cross-react with components of the GBM has not been resolved. Data recently published point at intra-GBM-associated nucleosomes as target for the nephritogenic autoantibodies. Colocalization IEM has demonstrated that autoantibodies and experimental antibodies against DNA, histones, or transcription factors like TATA box-binding protein colocalize in the EDS. By using terminal transferase in situ nick-end labeling in combination with immune electron microscopy to detect DNA specifically in human and murine SLE kidneys, we were able to detect DNA within the EDS of nephritic glomeruli that corresponded with the detected autoantibodies.

Clinical and serological correlates of antinucleosome antibodies in South Africans with systemic lupus erythematosus

Antinucleosome antibodies (AnuA) are increasingly recognized as an important biomarker in the diagnosis and subset stratification of patients with systemic lupus erythematosus (SLE). The aim of the study was to determine the sensitivity, specificity, and clinico-serological correlates of AnuA in black South Africans with SLE. We performed a cross-sectional study of 86 SLE patients attending a tertiary center and 87 control subjects. AnuA were tested using a second-generation enzyme-linked immunosorbent assay (ELISA). The sensitivity, specificity, positive predictive value, and negative predictive value of AnuA were 45.3, 94.3, 88.6, and 63.6%, respectively. The presence of AnuA were strongly associated with the co-presence of anti-dsDNA antibodies (OR = 3.4, p < 0.0005) and antihistone antibodies (OR = 15.7, p < 0.00001). Patients who were seropositive for AnuA were more likely to have skin involvement (discoid lupus and/or malar rash) and had higher SLE disease activity index (SLEDAI) scores and Systemic Lupus International Collaborative Clinics/American College of Rheumatology (SLICC/ACR) damage scores (p < 0.05). IgG anticardiolipin antibody (aCL) levels showed a significant correlation with AnuA ratios (p < 0.01). Our findings provide further evidence that AnuA are a sensitive and specific diagnostic biomarker in SLE. Moreover, our finding that the presence of AnuA, but not anti-dsDNA antibodies, are associated with worse SLICC/ACR damage scores suggest that AnuA may have a role in predicting disease outcome. The correlation between IgG aCL and AnuA is a novel finding that merits further studies to determine possible common peptide specificities of the antibodies.

Anti-chromatin (anti-nucleosome) antibodies

Chromatin is the native complex of histones and DNA found in the cell nucleus of eukaryotes. The fundamental subunit of chromatin is the nucleosome, which is composed of a core particle in which 146 bp of helical DNA are wrapped around an octamer made up of two H2A-H2B dimers that surround an H3-H4 tetramer. The prevalence of anti-chromatin (nucleosome) antibodies in systemic lupus erythematosus (SLE) varies from 50% to 90%, being similar to that of the classical positive LE cell. The presence of these antibodies can be used, in conjunction with clinical findings and other laboratory tests, to help in the diagnosis of SLE and drug induced lupus. The presence of anti-chromatin antibodies has also been linked to glomerulonephritis in SLE patients.

TLR9 in health and disease

Toll-like receptor 9 (TLR9) is specialized for the recognition of pathogenic nucleic acids. TLR9 is expressed in intracellular compartments where it responds specifically to pathogen DNA. Several factors contribute to the ability of TLR9 to discriminate between self and foreign DNA. Regulatory mechanisms of the innate and adaptive immune system exist that balance the immune responses mediated by TLR9. Short synthetic CpG oligodeoxynucleotides are used to induce controlled and directed TLR9-dependent stimulation and are effective immune modulators in preclinical and clinical studies. This review will summarize the interplay between TLR9-dependent opposing stimulatory and regulatory effects in innate and adaptive immunity.

Nucleosomal DNA Fragments in Autoimmune Diseases

The inadequate response of immune cells to circulating apoptotic products, such as nucleosomal DNA fragments, is assumed to be a potent stimulus for the production of autoantibodies during the pathogenesis and progression of systemic lupus erythematosus (SLE). Here, we analyzed the levels of circulating nucleosomes, caspases, and C-reactive protein in sera of 244 individuals with various autoimmune diseases (155 with autoimmune hepatic disorders, 25 with ANCA-associated vasculitis, and 64 with various connective tissue diseases), and 32 healthy controls. Nucleosomes and caspase activities were significantly elevated in sera of patients with hepatic autoimmune diseases, connective tissue diseases, and particularly in ANCA-associated vasculitis when compared with healthy individuals. Nucleosomes showed a correlation with caspases, and caspases with C-reactive protein, but nucleosomes did not correlate with C-reactive protein. Serum levels of the apoptotic products, nucleosomes, and caspases are increased in various autoimmune diseases but may not be solely responsible for antinucleosome antibody production in SLE patients. It remains to be clarified whether qualitative changes in nucleosomes are linked with pathogenesis and disease progression in SLE.

Application of a static fluorescence-based cytometer: the CellScan in clinical immunology

The CellScan system is a laser scanning cytometer which enables repetitive fluorescence intensity (FI) and polarization (FP) measurements in living cells, as a means of monitoring lymphocyte activation. By monitoring FP changes in peripheral blood lymphocytes (PBL) following exposure to antigenic stimuli, the CellScan may have a role in the diagnosis of autoimmune diseases. Monitoring changes in FI and FP in PBLs from patients with atherosclerosis following exposure to various stimuli, has illustrated the role of the immune system in the atherosclerotic process. The CellScan has also been evaluated as a diagnostic tool for drug-induced allergy, based on FP reduction in PBLs following incubation with the suspected drugs. FI and FP changes in cancer cells have been found to correlate with the cytotoxic effect of different anti-neoplastic drugs, illustrating the potential role of the CellScan system in clinical oncology. In conclusion, the CellScan is a promising new tool with a variety of applications in cell biology, immunology, cancer research and clinical pharmacology.

[Systemic lupus erythematosus and nucleosome]

The property of nucleosome in systemic lupus erythematosus (SLE) is reviewed. Nucleosome, complex of histone and DNA, is thought to have a pivotal role in pathogenesis of SLE. It is formed during apoptosis that is increased in peripheral lymphocytes of SLE. The concentration of nucleosome is elevated in SLE, probably related with disease activity. Nucleosome is speculated that the clearance from peripheral blood is decreased and that is modified by viral infection to become more immunogenic. Anti-nucleosome antibody is highly positive in majority of SLE, and is very specific for SLE except scleroderma and mixed connective tissue disease. This antibody is thought as a diagnostic marker and probably an activity marker for SLE. Anti-nucleosome antibody forms immune complex with nucleosome. As histone has strong positive charge, it is demonstrated that this nucleosome/anti-nucleosome complex is bound to negatively charged heparan sulfate of glomerular basement membrane in kidney. Then, complements bind to this antibody to generate lupus glomerulonephritis. Although main site of apoptosis in SLE is considered as lymphocytes, we experienced a case with SLE who had liver dysfunction with elevated soluble Fas ligand (sFasL) and apoptosis in her hepatocytes in the active stage of SLE. We measured serum sFasL, and found the relation of sFasL and liver involvement in active SLE. As major source of nucleosome should be apoptosis of lymphocytes in SLE, hepatocytes could be another candidate of apoptosis in some SLE.

Abnormal Fas/FasL and caspase-3-mediated apoptotic signaling pathways of T lymphocyte subset in patients with systemic lupus erythematosus

OBJECTIVES

To explore the relationships between Fas-FasL-mediated signaling pathway and apoptosis disturbance of T lymphocyte subset in patients with SLE.

METHODS

Flow cytometry was used to determine the percentage of apoptotic lymphocytes and necrotic lymphocytes by AnnexinV-FITC/PI double staining. Cell surface expression rates of Fas, FasL, and intracellular expression rates of activated caspase-3 were evaluated by two-color flow cytometry analysis in peripheral T lymphocyte subsets of SLE patients with inactive disease (n=22) and with active disease (n=17). The serum concentration of anti-nucleosome antibodies in SLE patients were assayed by ELISA immunoassay methods. Health volunteers (n=13) served as controls.

RESULTS

The percentage of early apoptotic cells was enhanced in patients with active disease (P=0.001, vs. control) and in patients with inactive disease (P=0.004, vs. control). Compared with health control, the percentage of necrotic cells was significant higher in patients with active disease (P=0.001). The percentages of CD4(+)T cells expressing Fas (P=0.023, vs. control) and FasL (P=0.001, vs. control) were increased in patients with active disease. But there were no obvious differences of expression rates of Fas and FasL on T cell subset between two disease groups (P>0.05). In patients with active disease the percentage of CD4(+)T cells or CD8(+)T cells expressing intracellular activated caspase-3 significantly increased compared to inactive disease patients (P=0.018, P=0.027, respectively) and health controls (P=0.001, P=0.001, respectively). The serum concentration of anti-nucleosome antibodies was strikingly higher in patients with active disease (P=0.002, vs. patients with inactive disease; P=0.001, vs. control, respectively), however, the serum concentration of anti-nucleosome antibodies was not obviously different between patients with inactive disease and health control group (P=0.473). The percentage of apoptotic cells correlated with the serum concentration of anti-nucleosome antibodies in SLE patients (r(s)=0.350, P=0.031).

CONCLUSIONS

Apoptosis of T lymphocyte subset in SLE patients increases. CD4(+)T cells are a state of active apoptosis. Fas/FasL-mediated apoptotic pathways are especially important for CD4(+)T cells undergoing apoptosis in SLE patients with active disease. Increased Fas expression results in a higher susceptibility to Fas-mediated apoptosis, which contributes to the increased levels of intracellular activated caspase-3 and accelerates apoptosis of T lymphocytes. The degree of lymphocytic apoptosis disturbance correlates with the level of anti-nucleosome antibodies in the circulation. Acceleration of lymphocytic apoptosis plays important roles in immune pathologic injury and immune regulation dysfunction.

Nucleosome autoantibodies

The nucleosome is a large protein-nucleic acid complex involved in DNA packing and in controlling genetic information. Under circumstances described below, this component, normally sequestered in the cell nucleus, is released into the extracellular milieu and then is easily accessible to cells of the immune system. For still not completely understood reasons, nucleosomes become immunogenic under particular conditions. Thus, anti-nucleosome autoantibodies (autoAb) have been described in connective tissue diseases and especially in systemic lupus erythematosus (SLE). This review describes the mechanisms leading to nucleosome production and anti-nucleosome autoimmunity, as well as the pathogenesis associated with nucleosomes.

Environmental adjuvants, apoptosis and the censorship over autoimmunity

Alterations during apoptosis lead to the activation of autoreactive T cells and the production of autoantibodies. This article discusses the pathogenic potential of cells dying in vivo, dissecting the role of signals that favor immune responses (adjuvants) and the influence of genetic backgrounds. Diverse factors determine whether apoptosis leads or not to a self-sustaining, clinically apparent autoimmune disease. The in vivo accumulation of uncleared dying cells per se is not sufficient to cause disease. However, dying cells are antigenic and their complementation with immune adjuvants causes lethal diseases in predisposed lupus-prone animals. At least some adjuvant signals directly target the function and the activation state of antigen presenting cells. Several laboratories are aggressively pursuing the molecular identification of endogenous adjuvants. Sodium monourate and the high mobility group B1 protein (HMGB1) are, among those identified so far, well known to rheumatologists. However, even the complementation of apoptotic cells with potent adjuvant signals fail to cause clinical autoimmunity in most strains: autoantibodies generated are transient, do not undergo to epitope/spreading and do not cause disease. Novel tools for drug development will derive from the molecular identification of the constraints that prevent autoimmunity in normal subjects.

The Relevance of Autoantigen Source and Cutoff Definition in Antichromatin (Nucleosome) Antibody Immunoassays

In the last few years, several reports have shown that chromatin (nucleosome) represents the main autoantigen-immunogen in systemic lupus erythematosus (SLE) and that specific antibodies are an important marker of the disease. To verify the clinical sensitivity and specificity of antinucleosome autoantibodies (ANuAs), we evaluated three ELISA immunoassay methods using different autoantigen preparations: Quanta Lite Chromatin, Medizym Anti-nucleo, and Nucleosome IgG Elisa. We compared the results with those obtained using two ELISA assays for determining anti-native DNA (anti-nDNA) antibodies: Axis-Shield and EliA dsDNA. We tested sera from 321 patients: 101 with SLE and 220 controls-48 with infectious diseases; 73 with autoimmune rheumatic disease (20 with rheumatoid arthritis, 30 with systemic sclerosis, and 23 with primary Sjögren's syndrome), and 99 healthy subjects. Using the manufacturer-recommended cutoff, the sensitivity for the three kits was 69%, 78%, and 74%, and specificity was 100%, 94.6%, and 95.0%, respectively. Using the cutoff corresponding to 95% specificity, the sensitivity of the methods for the ANuA assay was 86%, 77%, and 74%-higher than obtained with the two ELISA methods for anti-nDNA (65% and 64%). This study demonstrates that (1) the commercial reagents employed in clinical laboratories for ANuA detection show good sensitivity and high specificity; (2) ANuAs are more sensitive than anti-nDNA antibodies for diagnosing SLE; and (3) different solid-phase antigen preparations and methods used to define cutoff levels may affect a test's clinical performance.

The abnormal apoptosis of T cell subsets and possible involvement of IL-10 in systemic lupus erythematosus

To study the apoptosis of lymphocyte subpopulations in systemic lupus erythematosus (SLE) patients and the possible role of IL-10 in this apoptosis involved in the pathogenesis of SLE, three color fluorescence and flow cytometry were used to investigate the early apoptosis of lymphocyte subsets from freshly separated or cultured peripheral blood mononuclear cells (PBMCs). ELISA was employed to detect the levels of IL-10 in serum and the levels of sFas and sFasL in cultured PBMC supernatants, and the results of sFas and sFasL were confirmed by real-time PCR of Fas and FasL mRNA. The results showed that in cells from SLE patients, the apoptosis of CD3+, CD4+, and CD8+ T cells was distinctly increased, and the percentage of CD4+ cells and the CD4/CD8 ratio was significantly decreased, as compared with normal controls. The apoptosis of T lymphocytes cultured with SLE serum was markedly higher than that of cells cultured with control's serum. Blockade of interleukin-10 (IL-10) activation by an anti-IL-10 antibody reduced the SLE serum induced apoptosis of CD4+ and CD8+ T cells. The levels of sFas and sFasL in the culture supernatant and Fas and FasL mRNA expressions in cultured cells were significantly higher in the SLE serum-cultured groups, but decreased evidently in the presence of the anti-IL-10 antibody. Above findings suggested that SLE cells showed abnormally high apoptosis of T lymphocytes, especially of the CD4+ subpopulation, resulting in a decreased CD4/CD8 ratio. The high percentage of apoptotic T cells in SLE patients may be related to the high levels of IL-10 in SLE serum, as IL-10 may induce the abnormally activated T cells to trigger apoptosis via the Fas-FasL pathway.

[Interstitial lung disease: auto-antibodies in routine practice]

The clinical, computed tomography, cytological, and histological aspects of interstitial lung disease complicating an autoimmune disease lack specificity. Search for autoantibodies in the serum is thus warranted once the essentially clinical diagnosis has been established. An exhaustive history taking should aim at identifying extrathoracic elements of a possible systemic autoimmune disease. The battery of the biological tests which can be useful are discussed here in light of the diagnostic, prognostic, therapeutic, and even conceptual aspects of the disease. For the clinician, a simplified analysis of the main methods and the interpretation of immunological tests is discussed together with new tools currently under development.

Defects in the disposal of dying cells lead to autoimmunity

The fast and efficient uptake of dying cells is of main importance to prevent contact of the immune system with intracellular autoantigens. Insufficient clearance of the latter is discussed to drive the humoral autoimmune response in systemic lupus erythematosus. Many adaptor molecules and receptors are involved in the recognition of dying cells. In this paper we focus on the involvement of phosphatidylserine, glycoproteins, and complement and DNaseI in the clearance of apoptotic and necrotic cells, respectively. Furthermore, extracellular danger signals released from necrotic cells are discussed and the uptake process of primary necrotic cells is investigated in detail. Last but not least, the character and origin of clearance defects observed in some systemic lupus erythematosus patients is presented.