Nuclear antigen histone H1 is primarily involved in lupus erythematosus cell formation

Pathogenesis of systemic lupus erythematosus: risks, mechanisms and therapeutic targets

Research elucidating the pathogenesis of systemic lupus erythematosus (SLE) has defined two critical families of mediators, type I interferon (IFN-I) and autoantibodies targeting nucleic acids and nucleic acid-binding proteins, as fundamental contributors to the disease. On the fertile background of significant genetic risk, a triggering stimulus, perhaps microbial, induces IFN-I, autoantibody production or most likely both. When innate and adaptive immune system cells are engaged and collaborate in the autoimmune response, clinical SLE can develop. This review describes recent data from genetic analyses of patients with SLE, along with current studies of innate and adaptive immune function that contribute to sustained IFN-I pathway activation, immune activation and autoantibody production, generation of inflammatory mediators and tissue damage. The goal of these studies is to understand disease mechanisms, identify therapeutic targets and stimulate development of therapeutics that can achieve improved outcomes for patients.

Advances in SLE classification criteria

This year, the American College of Rheumatology (ACR) 1982 classification criteria for systemic lupus erythematosus (SLE) celebrate their 40th anniversary. From this start, the quest for optimal SLE criteria has led to the 1997 ACR update, the 2012 publication of the Systemic Lupus International Collaborating Clinics (SLICC) criteria, and, in 2019, the European League Against Rheumatism (EULAR)/ACR classification criteria. The latter have since been externally validated in more than two dozen studies and have become the gold standard inclusion criterion of SLE clinical trials. This comprehensive review attempts to follow the evolving success story of SLE classification, highlighting relevant decisions and their rationale, and discussing consequences for the way SLE is defined and managed.

Neutrophils in the Pathogenesis of Rheumatoid Arthritis and Systemic Lupus Erythematosus: Same Foe Different M.O

Dysregulated neutrophil activation contributes to the pathogenesis of autoimmune diseases including rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE). Neutrophil-derived reactive oxygen species (ROS) and granule proteases are implicated in damage to and destruction of host tissues in both conditions (cartilage in RA, vascular tissue in SLE) and also in the pathogenic post-translational modification of DNA and proteins. Neutrophil-derived cytokines and chemokines regulate both the innate and adaptive immune responses in RA and SLE, and neutrophil extracellular traps (NETs) expose nuclear neoepitopes (citrullinated proteins in RA, double-stranded DNA and nuclear proteins in SLE) to the immune system, initiating the production of auto-antibodies (ACPA in RA, anti-dsDNA and anti-acetylated/methylated histones in SLE). Neutrophil apoptosis is dysregulated in both conditions: in RA, delayed apoptosis within synovial joints contributes to chronic inflammation, immune cell recruitment and prolonged release of proteolytic enzymes, whereas in SLE enhanced apoptosis leads to increased apoptotic burden associated with development of anti-nuclear auto-antibodies. An unbalanced energy metabolism in SLE and RA neutrophils contributes to the pathology of both diseases; increased hypoxia and glycolysis in RA drives neutrophil activation and NET production, whereas decreased redox capacity increases ROS-mediated damage in SLE. Neutrophil low-density granulocytes (LDGs), present in high numbers in the blood of both RA and SLE patients, have opposing phenotypes contributing to clinical manifestations of each disease. In this review we will describe the complex and contrasting phenotype of neutrophils and LDGs in RA and SLE and discuss their discrete roles in the pathogenesis of each condition. We will also review our current understanding of transcriptomic and metabolomic regulation of neutrophil phenotype in RA and SLE and discuss opportunities for therapeutic targeting of neutrophil activation in inflammatory auto-immune disease.

Caught in a Trap? Proteomic Analysis of Neutrophil Extracellular Traps in Rheumatoid Arthritis and Systemic Lupus Erythematosus

Neutrophil Extracellular Traps (NETs) are implicated in the development of auto-immunity in diseases such as rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE) through the externalization of intracellular neoepitopes e.g., dsDNA and nuclear proteins in SLE and citrullinated peptides in RA. The aim of this work was to use quantitative proteomics to identify and measure NET proteins produced by neutrophils from healthy controls, and from patients with RA and SLE to determine if NETs can be differentially-generated to expose different sets of neoepitopes. Ultra-pure neutrophils (>99%) from healthy individuals (n = 3) and patients with RA or SLE (n = 6 each) were incubated ± PMA (50 nM, PKC super-activator) or A23187 (3.8 μM, calcium ionophore) for 4 h. NETs were liberated by nuclease digestion and concentrated onto Strataclean beads prior to on-bead digestion with trypsin. Data-dependent LC-MS/MS analyses were conducted on a QExactive HF quadrupole-Orbitrap mass spectrometer, and label-free protein quantification was carried out using Progenesis QI. PMA-induced NETs were decorated with annexins, azurocidin and histone H3, whereas A23187-induced NETs were decorated with granule proteins including CAMP/LL37, CRISP3, lipocalin and MMP8, histones H1.0, H1.4, and H1.5, interleukin-8, protein-arginine deiminase-4 (PADI4), and α-enolase. Four proteins were significantly different between PMA-NETs from RA and SLE neutrophils (p < 0.05): RNASE2 was higher in RA, whereas MPO, leukocyte elastase inhibitor and thymidine phosphorylase were higher in SLE. For A23187-NETs, six NET proteins were higher in RA (p < 0.05), including CAMP/LL37, CRISP3, interleukin-8, MMP8; Thirteen proteins were higher in SLE, including histones H1.0, H2B, and H4. This work provides the first, direct comparison of NOX2-dependent (PMA) and NOX2-independent (A23187) NETs using quantitative proteomics, and the first direct comparison of RA and SLE NETs using quantitative proteomics. We show that it is the nature of the stimulant rather than neutrophil physiology that determines NET protein profiles in disease, since stimulation of NETosis in either a NOX2-dependent or a NOX2-independent manner generates broadly similar NET proteins irrespective of the disease background. We also use our proteomics pipeline to identify an extensive range of post-translationally modified proteins in RA and SLE, including histones and granule proteins, many of which are known targets of auto-antibodies in each disease.

Autoantibodies Recognizing Secondary NEcrotic Cells Promote Neutrophilic Phagocytosis and Identify Patients With Systemic Lupus Erythematosus

Deficient clearance of apoptotic cells reportedly contributes to the etiopathogenesis of the autoimmune disease systemic lupus erythematosus (SLE). Based on this knowledge, we developed a highly specific and sensitive test for the detection of SLE autoantibodies (AAb) utilizing secondary NEcrotic cell (SNEC)-derived material as a substrate. The goal of the present study was to validate the use of SNEC as an appropriate antigen for the diagnosis of SLE in large cohort of patients. We confirmed the presence of apoptotically modified autoantigens on SNEC (dsDNA, high mobility group box 1 protein, apoptosis-associated chromatin modifications, e.g., histones H3-K27-me3; H2A/H4 AcK8,12,16; and H2B-AcK12). Anti-SNEC AAb were measured in the serum of 155 patients with SLE, 89 normal healthy donors (NHD), and 169 patients with other autoimmune connective tissue diseases employing SNEC-based indirect enzyme-linked immunosorbent assay (SNEC ELISA). We compared the test performance of SNEC ELISA with the routine diagnostic tests dsDNA Farr radioimmunoassay (RIA) and nucleosome-based ELISA (anti-dsDNA-NcX-ELISA). SNEC ELISA distinguished patients with SLE with a specificity of 98.9% and a sensitivity of 70.6% from NHD clearly surpassing RIA and anti-dsDNA-NcX-ELISA. In contrast to the other tests, SNEC ELISA significantly discriminated patients with SLE from patients with rheumatoid arthritis, primary anti-phospholipid syndrome, spondyloarthropathy, psoriatic arthritis, and systemic sclerosis. A positive test result in SNEC ELISA significantly correlated with serological variables and reflected the uptake of opsonized SNEC by neutrophils. This stresses the relevance of SNECs in the pathogenesis of SLE. We conclude that SNEC ELISA allows for the sensitive detection of pathologically relevant AAb, enabling its diagnostic usage. A positive SNEC test reflects the opsonization of cell remnants by AAb, the neutrophil recruitment to tissues, and the enhancement of local and systemic inflammatory responses.

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.

The assessment of serum-mediated phagocytosis of necrotic material by polymorphonuclear leukocytes to diagnose and predict the clinical features of systemic lupus erythematosus: an observational longitudinal study

BACKGROUND

Serum-mediated phagocytosis of antibody- and complement-opsonized necrotic cell material (NCM) by polymorphonuclear leukocytes can be quantified by using a flow cytometry-based assay. The phagocytosis of necrotic cell material (PNC) assay parallels the well-known lupus erythematosus cell test. In this study, we aimed to investigate the diagnostic accuracy of the assay and the relationship with clinical manifestations and disease activity in systemic lupus erythematosus (SLE).

METHODS

The diagnostic accuracy for SLE diagnosis of the PNC assay was studied by cross-sectional assessment of blood samples from 148 healthy control subjects and a multicenter rheumatic group (MRG) of 529 patients with different rheumatic symptoms. A cohort of 69 patients with an established SLE diagnosis (SLE cohort) underwent longitudinal clinical and laboratory follow-up for analysis of the temporal relationships between PNC positivity and specific clinical manifestations.

RESULTS

In 35 of 529 MRG patients, 13 of whom had SLE, the PNC assay result was positive. Combined positivity of the PNC assay and anti-double-stranded DNA antibodies increased specificity and positive predictive value for SLE diagnosis to 0.99 and 0.67, respectively. In the longitudinal study, 42 of 69 SLE cohort patients had positive results in the PNC assay at least once. PNC assay positivity was associated with current hematological manifestations and could predict mucocutaneous manifestations. When combined with hypocomplementemia, PNC positivity preceded increased Systemic Lupus Erythematosus Disease Activity Index 2000 score, glomerulonephritis, and alopecia.

CONCLUSIONS

Serum-mediated PNC by polymorphonuclear leukocytes is commonly but not exclusively seen in patients with SLE. The PNC assay may be used in follow-up of patients with SLE and, especially in combination with other routinely assessed laboratory tests, may help to predict flares and different clinical manifestations, including glomerulonephritis. Our results encourage further development of the PNC assay as a complementary laboratory tool in management of patients with SLE.

Combination of autoantibodies against different histone proteins influences complement-dependent phagocytosis of necrotic cell material by polymorphonuclear leukocytes in systemic lupus erythematosus

OBJECTIVE

Polymorphonuclear leukocytes (PMN) with autoantibody-coated engulfed necrotic cell material (NC) are frequently seen in systemic lupus erythematosus (SLE). We evaluated the roles of complement, different antihistone antibodies (anti-H ab), and oxidative burst in the phagocytosis of NC by PMN, as well as association to disease activity and clinical phenotype in SLE.

METHODS

ELISA and immunoblot were used to measure antibodies to different histone proteins in sera from patients with SLE and complement-deficient individuals. Phagocytosis of NC by PMN and oxidative burst activity was assessed by flow cytometry.

RESULTS

A clearly increased phagocytosis of NC was seen in patients with active SLE, which was associated with high levels of anti-H ab concentrations and oxidative burst activity. The complement system contributed to efficient phagocytosis of NC by PMN through activation of the classical pathway, and the phagocytosis was mediated by FcγRIIA, FcγRIIIB, and CR1 in combination. A pattern of high phagocytosis, consumption of classical pathway components, and a broad anti-H ab repertoire was seen particularly in patients with nephritis and serositis. The combination of antibodies to several different histone proteins, often with anti-DNA antibodies, promoted an efficient uptake of NC, whereas antibodies against only histone H1 or a few histones seemed to be of less importance.

CONCLUSION

The distributions of specificities among anti-H ab are of great importance in the complement-dependent phagocytosis of debris from NC in SLE. Measurement of anti-H ab could be useful in monitoring of this disease and contribute to improved understanding of the autoimmune process.

Nucleic acid-associated autoantigens: pathogenic involvement and therapeutic potential

Autoimmunity to ubiquitously expressed macromolecular nucleic acid-protein complexes such as the nucleosome or the spliceosome is a characteristic feature of systemic autoimmune diseases. Disease-specificity and/or association with clinical features of some of these autoimmune responses suggest pathogenic involvement which, however, has been proven in only a few cases so far. Although the mechanisms leading to autoimmunity against nucleic acid-containing complexes are still far from being fully understood, there is increasing experimental evidence that the nucleic acid component may act as a co-stimulator or adjuvans via activation of nucleic acid-binding receptor systems such as Toll-like receptors in antigen-presenting cells. Dysregulated apoptosis and inappropriate stimulation of nucleic acid-sensing receptors may lead to loss of tolerance against the protein components of such complexes, activation of autoreactive T cells and formation of autoantibodies. This has been demonstrated to occur in systemic lupus erythematosus and seems to represent a general mechanism that may be crucial for the development of systemic autoimmune diseases. This review provides a comprehensive overview of the most thoroughly-characterized nucleic acid-associated autoantigens, describing their structure and biological function, as well as the nature and pathogenic importance of the reactivities directed against them. Furthermore, recent advances in immunotherapy such as antigen-specific approaches targeted at nucleic acid-binding antigens are discussed.

Remnants of secondarily necrotic cells fuel inflammation in systemic lupus erythematosus

OBJECTIVE

Patients with systemic lupus erythematosus (SLE) are often characterized by cellular as well as humoral deficiencies in the recognition and phagocytosis of dead and dying cells. The aim of this study was to investigate whether the remnants of apoptotic cells are involved in the induction of inflammatory cytokines in blood-borne phagocytes.

METHODS

We used ex vivo phagocytosis assays comprising cellular and humoral components and phagocytosis assays with isolated granulocytes and monocytes to study the phagocytosis of secondarily necrotic cell-derived material (SNEC). Cytokines were measured by multiplex bead array technology.

RESULTS

We confirmed the impaired uptake of various particulate targets, including immunoglobulin-opsonized beads, by granulocytes and monocytes from patients with SLE compared with healthy control subjects. Surprisingly, blood-borne phagocytes from two-thirds of the patients with SLE took up SNEC, which was rarely phagocytosed by phagocytes from healthy control subjects or patients with rheumatoid arthritis. Supplementation of healthy donor blood with IgG fractions derived from patients with SLE transferred the capability to take up SNEC to the phagocytes of healthy donors. Phagocytosis-promoting immune globulins also induced secretion of huge amounts of cytokines by blood-borne phagocytes following uptake of SNEC.

CONCLUSION

Opsonization of SNEC by autoantibodies from patients with SLE fosters its uptake by blood-borne monocytes and granulocytes. Autoantibody-mediated phagocytosis of SNEC is accompanied by secretion of inflammatory cytokines, fueling the inflammation that contributes to the perpetuation of autoimmunity in SLE.

Interaction of histones with phospholipids—implications for the exposure of histones on apoptotic cells

The generation of autoantibodies against chromatin is a hallmark of the multifactorial autoimmune disease systemic lupus erythematosous (SLE). Impaired clearance of apoptotic cells together with the release of nuclear autoantigens are supposed to contribute to the loss of self-tolerance in SLE. Phospholipids such as phosphatidylserine (PS) and phosphatidylethanolamine (PE) are exposed on the surfaces of apoptotic cells and on apoptotic blebs. Also histones/nucleosomes can be detected on apoptotic cells; however, their binding motifs are still unknown. Therefore, we investigated the interaction of PS, PE, phosphatidylcholine (PC), and cardiolipin (CL) with histones H1, H2A, H2B, H3, and H4 by surface plasmon resonance (SPR). Strong binding to phospholipids was found for all histones, with H2A displaying the highest binding affinity to all phospholipids investigated. Hence, phospholipids including PS and PE may contribute to the binding of histones to surfaces and blebs of apoptotic cells. Moreover, histones/nucleosomes complexed to uningested apoptotic membrane structures may foster autoimmunity towards nuclear compounds.

[Analysis of autoantigens in patients with systemic lupus erythematosus by using proteomic approach]

Analysis of autoantibodies/antigens has very important impact for investigation of the pathogenesis of autoimmune diseases, including systemic lupus erythematosus (SLE). Recent progress has enabled us to detect and analyze the autoantibodies/antigens easily by using a proteomics approach. By proteomics, we can directly detect proteins as gene products as well as their alterations by post-translational modification and internal abscission which are characteristically observed in proteins. For example, we pick up autoantigens of interest as spots through combination of two-dimensional electrophoresis and western blot, and identify them by analysis using mass spectrometry. These methods allow us to use clinical specimens, including various tissues as a source of autoantigens. In this review, we introduce application of proteomics approach to autoimmune diseases, referring to our study of the autoantigens detected by anti-neuronal antibodies in SLE patients with central nervous system involvement.

Engulfed cell remnants, and not cells undergoing apoptosis, constitute the LE-cell phenomenon

The LE cell has been one of the first immunological signs of active systemic lupus erythematosus, included into the ACR criteria. LE cells consist of a phagocyte engulfing material of disputed origin, which was interpreted as either cellular remnants from necrotic cells or as early apoptotic cells. It is well established that LE cell formation is dependent on autoantibodies against the linker histone H1. In view of this fact, we investigated whether anti-histone H1 antibodies and LE cell positive sera bound to cells where apoptosis had been induced by gliotoxin or actinomycin D or which were necrotic after heating. Necrotic cell remnants, but not (early) apoptotic cells were bound by anti-histone H1 antibodies and LE cell positive sera, establishing that the process of LE cell formation, which is dependent on anti-H1 binding, leads to engulfment of necrotic (or late apoptotic) material, but not of early apoptotic cells.

Anticorps antihistones au cours du lupus érythémateux systémique, comparaison entre trois techniques : Elisa, dot blot et immunotransfert

AIMS

The purpose of our study is to determine and compare the sensitivity of an enzyme linked immunosorbent assay (ELISA), a dot blot assay and an immunoblot assay for the detection of the IgG class antihistones antibodies in a population of systemic lupus erythematosus. The correlation between antihistones antibodies and the main clinical features of SLE or between antihistones antibodies and the presence of anti-double-stranded-DNA antibodies were analysed.

MATERIALS AND METHODS

Serum samples from 126 systemic lupus erythematosus patients, classified according to the criteria of the American College of Rheumatology, were analysed for the presence of antihistones antibodies using a dot blot assay and an ELISA. Antihistones subfractions antibodies were assessed using the immunoblot technique on 88 out of the 126 sera. Serum samples from 50 blood-donors were analyzed as negative controls.

RESULTS

The sensitivity of antihistones antibodies assessed by dot blot assay and ELISA was 69% and 54% respectively, and was lower than that of anti-double-stranded-DNA antibodies (83%). The sensitivity of the immunoblot assay for the detection of antihistones antibodies was 72%. Incidence of autoantibodies against histones H1, H2 A, H2B, H3 and H4 was 60%, 53%, 48%, 36% and 29.5% respectively. We found a correlation between the presence of antihistones antibodies, detected by the dot blot assay and ELISA, and the presence of anti-double-stranded-DNA antibodies. Antihistones antibodies detected by ELISA were correlated with renal disease in systemic lupus erythematosus; they showed a specificity, a positive and a negative predictive value for renal disease in systemic lupus erythematosus higher than those of anti-double-stranded-DNA antibodies.

CONCLUSIONS

The sensitivity of the dot blot assay for the detection of antihistones antibodies is better than that of ELISA, but the latter technique could detect some cases negative by ELISA. Antihistones antibodies detected by ELISA have an important predictive value in the renal complications in systemic lupus erythematosus, better than that of AdsDNA. Antibodies to histone H1 were the most frequent antihistones autoandibodies in systemic lupus erythematosus and they were highly correlated with anti-double-stranded-DNA antibodies and renal disease.

Cross-recognition between histones and La/SSB may account for anti-DNA reactivity in SLE patients

Antibodies to La/SSB are detected in sera of patients with primary Sjogren's syndrome (pSS) and systemic lupus erythematosus (SLE). The vast majority of anti-La/SSB positive sera contain antibodies directed towards a linear B-cell epitope of La/SSB spanning the sequence 349-364aa (pep349-364). The aim of this study was to evaluate the fluctuation of antibody levels to major B-cell epitopes of La/SSB over time and investigate for their possible crossreactions. Sequential sera from 15 SLE and 15 pSS patients, followed from 3 to 10 years were obtained. All patients with SLE were positive for anti-Ro/SSA, anti-La/SSB and anti-dsDNA antibodies and patients with pSS were positive for anti-Ro/SSA and anti-La/SSB antibodies. Sera from 30 patients with SLE without anti-La/SSB antibodies and 30 healthy individuals served as disease and negative control respectivelly. All sera tested for the presence of anti-pep349-364 antibodies, using a specific ELISA. Specific anti-pep349-364 IgG was purified from sera of SLE patients and evaluated for cross reactivity against dsDNA and histones. In all SLE sera the levels of anti-pep349-364 antibodies varied in time and fluctuated in parallel with anti dsDNA antibodies. Anti-pep349-364 IgG purified from 7 SLE patients. Five out of 7 were found to react with calf thymus DNA in ELISA. All purified (7/7) anti-pep349-364 IgG preparations reacted with histone H1 and failed to produce a positive immunofluorescence pattern in Crithidia luciliae anti-dsDNA assay which lacks histones. Competative inhibition experiments demonstrated that histone H1 could inhibit completely the binding of anti-pep349-364 IgG to pep349-364 while pep349-364 inhibited by 70% the binding of anti-pep349-364 IgG to histone H1. These findings indicate that a subgroup of SLE patients possess cross-reacting anti-histone H1 antibodies and anti-pep349-364 antibodies, which can be faulty considered as anti-dsDNA reactivity in regular ELISA techniques.

Autoantibody explosion in systemic lupus erythematosus: more than 100 different antibodies found in SLE patients

OBJECTIVE

Description of the various autoantibodies that can be detected in patients with systemic lupus erythematosus (SLE).

METHODS

A literature review, using the terms "autoantibody" and "systemic lupus erythematosus", was conducted to search for articles on autoantibodies in SLE, their target antigens, association with disease activity, or other clinical associations.

RESULTS

One hundred sixteen autoantibodies were described in SLE patients. These include autoantibodies that target nuclear antigens, cytoplasmic antigens, cell membrane antigens, phospholipid-associated antigens, blood cells, endothelial cells, and nervous system antigens, plasma proteins, matrix proteins, and miscellaneous antigens. The target of autoantibody, the autoantigen properties, autoantibody frequencies in SLE, as well as clinical associations, and correlation with disease activity are described for all 116 autoantibodies.

CONCLUSIONS

SLE is the autoimmune disease with the largest number of detectable autoantibodies. Their production could be antigen-driven, the result of polyclonal B cell activation, impaired apoptotic pathways, or the outcome of idiotypic network dysregulation.

Safety and efficacy of tumor necrosis factor ? blockade in systemic lupus erythematosus: An open-label study

OBJECTIVE

To investigate the safety of therapeutic tumor necrosis factor alpha (TNFalpha) blockade in patients with systemic lupus erythematosus (SLE), in whom this proinflammatory cytokine is significantly increased and may be involved in the disease pathogenesis.

METHODS

In an open-label study, 6 patients with moderately active SLE (4 with nephritis and 3 with arthritis refractory to other therapies) were given 4 300-mg doses of infliximab, a chimeric anti-TNFalpha antibody, in addition to immunosuppression with azathioprine or methotrexate.

RESULTS

The only significant adverse events observed were urinary tract infection in 3 patients, 1 of which was accompanied by Escherichia coli bacteremia, and a prolonged febrile episode of putatively viral origin in 1 of them. These patients had similar infectious conditions in the past. In none of the patients was it necessary to terminate the treatment prematurely. Levels of antibodies to double-stranded DNA and cardiolipin increased in 4 patients each, but this was not associated with a decrease in serum complement levels, with vascular events, or with flares. In contrast, disease activity declined during therapy. All 3 patients with joint involvement experienced remission of arthritis, which relapsed 8-11 weeks after the last infliximab infusion. In the 4 patients with lupus nephritis, proteinuria decreased significantly within 1 week after initiation of therapy and was diminished by > or = 60% within 8 weeks, remaining at low levels until the end of the observation period (at least several months).

CONCLUSION

Infliximab did not lead to adverse events related to an increase in SLE activity, although autoantibodies to double-stranded DNA and cardiolipin increased, as expected. This finding, coupled with the clinical improvement in the inflammatory manifestations of the disease, indicates that further study in larger controlled trials is warranted.

The autoimmune response to chromatin antigens in systemic lupus erythematosus: autoantibodies against histone H1 are a highly specific marker for SLE associated with increased disease activity

This study investigates specificity, sensitivity and concomitant presence of antibodies against histone H1 (H1), nucleosomes (NUC), chromatin (CHR) and dsDNA in patients with systemic lupus erythematosus (SLE), analyses their association with SLE disease activity and characterizes the immunodominant epitope reactivity of anti-H1 antibodies and its relation to SLE disease activity. In a cross-sectional study 394 sera of patients with various rheumatic diseases and healthy subjects were analysed by ELISA for antibodies against H1, NUC, CHR and dsDNA. In addition, a longitudinal analysis was performed that included 121 sequential serum samples derived from 16 SLE patients to assess the relation of these antibodies as well as antibodies to histone H2B to SLE disease activity. To assess epitope reactivity of anti-H1 antibodies overlapping synthetic peptides covering the entire H1 sequence were used. Anti-H1 antibodies yielded a sensitivity of approximately 45% and a specificity of over 98% for SLE, which was comparable to that found for anti-dsDNA antibodies. Anti-CHR and anti-NUC antibodies were of similar sensitivity but slightly (anti-CHR) or considerably (anti-NUC) less specific for SLE (95 and 85%, respectively). The sequential analysis revealed a strong correlation of anti-H1 antibodies with SLE disease activity that was better than the correlation of anti-dsDNA and anti-NUC antibodies, while only weak correlation was found for anti-CHR and anti-H2B antibodies. The immunodominant epitope for anti-HI was localised between amino acids 204 and 218 (pp204-218) and immune reactivity to this epitope also correlated with disease activity. Anti-H1 is a highly specific marker for SLE with a diagnostic value comparable to anti-dsDNA. A positive testing for anti-H1 indicates increased disease activity, as does the appearance of antibodies to its immunodominant epitope pp204-218.

Antinuclear antibody testing

The ANA test is an excellent screening test for patients with SLE and a few other connective tissue diseases. The LE cell preparation is an assay that is subjective and costly. Because of the presence of a superior screening test (the ANA) and superior specific auto-antibody tests, the author recommends that the use of LE cell preparations be discontinued. ANA screening tests may be performed either by indirect microscopic serology (usually IFA) or EIA. The latter technique is readily automated and many new products for this screening test have appeared in the past decade. The products differ, however, and laboratories are cautioned to test each in the context of the clinical needs of their clinicians. Proper use of the ANA test requires each laboratory to determine the cutoff used under their conditions of assay. Although either ANA screening test has a high negative predictive value in numerous studies, proper selection of patients to be tested is key to improving the predictive value of a positive result. The American College of Rheumatism criteria are reviewed and recommended as part of the patient selection process for this testing.