Genesis and evolution of antichromatin autoantibodies in murine lupus implicates T-dependent immunization with self antigen

Estrogen Receptor Alpha Signaling Is Responsible for the Female Sex Bias in the Loss of Tolerance and Immune Cell Activation Induced by the Lupus Susceptibility Locus Sle1b

The dramatic female sex bias observed in human lupus is thought to be due, at least in part, to estrogens. Using mouse models, we have shown that estrogens, acting through estrogen receptor alpha (ERα) promote lupus development and contribute significantly to the female sex bias observed in this disease. C57Bl/6 (B6) mice carrying the lupus susceptibility locus Sle1 locus exhibit immune cell hyperactivation and loss of tolerance, and the action of Sle1 displays a strong female sex bias. Previously, we showed that disruption of ERα completely eliminates the female sex bias in the effects of Sle1. Here we report that ERα signaling selectively modulates the action of Sle1b, one of the three subloci that together constitute Sle1. We observed that disruption of ERα signaling attenuated T cell hyperactivation, formation of spontaneous germinal centers, loss of tolerance, and the development of anti-chromatin autoantibodies in B6.Sle1b female mice, but had no impact on these phenotypes in B6.Sle1b male mice. In fact, disruption of ERα completely abolished the female sex bias that is seen in each of these phenotypes in B6.Sle1b mice. Strikingly, Sle1b-induced B cell hyperactivation, a female sex-specific manifestation of Sle1b, was completely abrogated by disruption of ERα in B6.Sle1b females. Altogether, these results demonstrate that ERα signaling is responsible for the female sex bias in the actions of Sle1b, and is absolutely required for the female-specific B cell hyperactivation phenotype associated with this lupus susceptibility locus. By contrast, we found that ERα signaling had no impact on Sle1a, the other Sle1 sublocus that exerts effects that show a female sex bias.

SLE presenting as demyelinative autoimmune visual loss

A healthy 38-year-old woman developed sudden unilateral vision loss due to retrobulbar optic neuritis in the wake of varicella-zoster virus infection. She had no further central nervous system (CNS) lesions. Antinuclear antibodies (ANA) and anti-aquaporin 4 antibodies were found, consistent with neuromyelitis optica (NMO). Later, serial MRIs showed dynamic short-segment and long-segment myelitis lesions, ANA titre increased and additional autoantibodies were found including anti-dsDNA, anti-chromatin/nucleosome and antiphospholipid antibodies. In that setting, NMO can be regarded a rare presenting manifestation of systemic lupus erythematosus (SLE). The relevant literature is reviewed and the implications of NMO spectrum disorder demyelinating syndromes as the first manifestation of SLE (with or without antiphospholipid syndrome) (APS) or their later development (in a patient diagnosed with SLE) as part of the spectrum of neuropsychiatric SLE are analysed in view of recent research developments in the field.

T-bet+CD11c+ B cells are critical for antichromatin immunoglobulin G production in the development of lupus

Background

A hallmark of systemic lupus erythematosus is high titers of circulating autoantibodies. Recently, a novel CD11c⁺ B-cell subset has been identified that is critical for the development of autoimmunity. However, the role of CD11c⁺ B cells in the development of lupus is unclear. Chronic graft-versus-host disease (cGVHD) is a lupus-like syndrome with high autoantibody production. The purpose of this study was to explore the role of CD11c⁺ B cells in the pathogenesis of lupus in cGVHD mice.

Methods

cGVHD was induced by an intraperitoneal injection of 5 × 10⁷ Bm12 splenocytes into B6 mice. Flow cytometry was used to analyze mice splenocytes and human samples. Magnetic beads were used to isolate mice B cells. Gene expression was determined by real-time quantitative polymerase chain reaction (RT-qPCR). Enzyme-linked immunosorbent assay (ELISA) was used to detect antibodies in serum and supernatants.

Results

The percentage and absolute number of CD11c⁺ B cells was increased in cGVHD-induced lupus, with elevated levels of antichromatin immunoglobulin (Ig)G and IgG2a in sera. CD11c⁺ plasma cells from cGVHD mice produced large amounts of antichromatin IgG2a upon stimulation. Depletion of CD11c⁺ B cells reduced antichromatin IgG and IgG2a production. T-bet was upregulated in CD11c⁺ B cells. Knockout of T-bet in B cells alleviated cGVHD-induced lupus. Importantly, the percentage of T-bet⁺CD11c⁺ B cells increased in lupus patients and positively correlated with serum antichromatin levels.

Conclusion

T-bet⁺CD11c⁺ B cells promoted high antichromatin IgG production in the lupus-like disease model cGVHD. In lupus patients, the percentage of T-bet⁺CD11c⁺ B cells was elevated and positively correlated with antichromatin antibodies. The findings provide potential therapeutic insight into lupus disease treatment.

Electronic supplementary material

The online version of this article (doi:10.1186/s13075-017-1438-2) contains supplementary material, which is available to authorized users.

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.

Anti-DNA antibodies--quintessential biomarkers of SLE

Antibodies that recognize and bind to DNA (anti-DNA antibodies) are serological hallmarks of systemic lupus erythematosus (SLE) and key markers for diagnosis and disease activity. In addition to common use in the clinic, anti-DNA antibody testing now also determines eligibility for clinical trials, raising important questions about the nature of the antibody-antigen interaction. At present, no 'gold standard' for serological assessment exists, and anti-DNA antibody binding can be measured with a variety of assay formats, which differ in the nature of the DNA substrates and in the conditions for binding and detection of antibodies. A mechanism called monogamous bivalency--in which high avidity results from simultaneous interaction of IgG Fab sites with a single polynucleotide chain--determines anti-DNA antibody binding; this mechanism might affect antibody detection in different assay formats. Although anti-DNA antibodies can promote pathogenesis by depositing in the kidney or driving cytokine production, they are not all alike, pathologically, and anti-DNA antibody expression does not necessarily correlate with active disease. Levels of anti-DNA antibodies in patients with SLE can vary over time, distinguishing anti-DNA antibodies from other pathogenic antinuclear antibodies. Elucidation of the binding specificities and the pathogenic roles of anti-DNA antibodies in SLE should enable improvements in the design of informative assays for both clinical and research purposes.

Intrinsic Differences in Donor CD4 T Cell IL-2 Production Influence Severity of Parent-into-F1 Murine Lupus by Skewing the Immune Response Either toward Help for B Cells and a Sustained Autoantibody Response or toward Help for CD8 T Cells and a Downregulatory Th1 Response

Using the parent-into-F1 model of induced lupus and (C57BL/6 × DBA2) F1 mice as hosts, we compared the inherent lupus-inducing properties of the two parental strain CD4 T cells. To control for donor CD4 recognition of alloantigen, we used H-2(d) identical DBA/2 and B10.D2 donor T cells. We demonstrate that these two normal, nonlupus-prone parental strains exhibit two different T cell activation pathways in vivo. B10.D2 CD4 T cells induce a strong Th1/CMI pathway that is characterized by IL-2/IFN-γ expression, help for CD8 CTLs, and skewing of dendritic cell (DC) subsets toward CD8a DCs, coupled with reduced CD4 T follicular helper cells and transient B cell help. In contrast, DBA/2 CD4 T cells exhibit a reciprocal, lupus-inducing pathway that is characterized by poor IL-2/IFN-γ expression, poor help for CD8 CTLs, and skewing of DC subsets toward plasmacytoid DCs, coupled with greater CD4 T follicular helper cells, prolonged B cell activation, autoantibody formation, and lupus-like renal disease. Additionally, two distinct in vivo splenic gene-expression signatures were induced. In vitro analysis of TCR signaling revealed defective DBA CD4 T cell induction of NF-κB, reduced degradation of IκBα, and increased expression of the NF-κB regulator A20. Thus, attenuated NF-κB signaling may lead to diminished IL-2 production by DBA CD4 T cells. These results indicate that intrinsic differences in donor CD4 IL-2 production and subsequent immune skewing could contribute to lupus susceptibility in humans. Therapeutic efforts to skew immune function away from excessive help for B cells and toward help for CTLs may be beneficial.

Estrogen receptor alpha signaling promotes Sle1-induced loss of tolerance and immune cell activation and is responsible for sex bias in B6.Sle1 congenic mice

Sex bias in lupus incidence is thought to be due, in part, to the ability of estrogens to promote loss of tolerance. Previously, we showed that estrogens promote lupus via estrogen receptor α (ERα). C57BL/6 (B6) mice carrying the Sle1 lupus susceptibility locus (B6.Sle1) display loss of tolerance and develop anti-nuclear antibodies and immune cell hyperactivation. The incidence of loss of tolerance in B6.Sle1 females is greater than in males. Here, we show that a deficiency of either estrogens or ERα attenuates loss of tolerance and autoantibody development in B6.Sle1 females. Furthermore, we demonstrate that immune cell activation in B6.Sle1 mice shows sex bias and that ERα deficiency diminishes this phenotype in B6.Sle1 females. Thus, estrogens, acting via ERα, control sex bias in the Sle1 phenotype. Furthermore, we show that ERα may impact the Sle1 phenotype by modulating the expression of Pbx1, one of genes that underlies the Sle1 locus.

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.

3-Nitrotyrosine: A biomarker of nitrogen free radical species modified proteins in systemic autoimmunogenic conditions

The free radical-mediated damage to proteins results in the modification of amino acid residues, cross-linking of side chains and fragmentation. l-Tyrosine and protein bound tyrosine are prone to attack by various mediators and reactive nitrogen intermediates to form 3-nitrotyrosine (3-NT). Activated macrophages produce superoxide (O2(·-)) and NO, which are converted to peroxynitrite ONO2(-). 3-NT formation is also catalyzed by a class of peroxidases utilizing nitrite and hydrogen peroxide as substrates. Evidence supports the formation of 3-NT in vivo in diverse pathologic conditions and 3-NT is thought to be a relatively specific marker of oxidative damage mediated by peroxynitrite. Free/protein-bound tyrosines are attacked by various RNS, including peroxynitrite, to form free/protein-bound 3-NT, which may provide insight into the etiopathogenesis of autoimmune conditions. The formation of nitrotyrosine represents a specific peroxynitrite-mediated protein modification; thus, detection of nitrotyrosine in proteins is considered as a biomarker for endogenous peroxynitrite activity. The peroxynitrite-driven oxidation and nitration of biomolecules may lead to autoimmune diseases such as systemic lupus. The subsequent release of altered proteins may enable them to act as antigen-inducing antibodies against self-proteins. Hence, tyrosine nitrated proteins can act as neoantigens and lead to the generation of autoantibodies against self proteins in various autoimmune disorders.

Autoantibodies in systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a multifactorial disorder with multigenic inheritance and various environmental factors implicated in its aetiopathogenesis. Despite the multiple mechanisms involved in the aetiology of SLE being elusive, recent studies have made progress in our understanding of the pathogenic mechanisms via abnormal regulation of cell-mediated and humoral immunity that lead to tissue damage. The heterogeneity of the clinical manifestations probably reflects the complexity of the disease pathogenesis itself. The immune system in SLE is characterised by a complex interplay between overactive B cells, abnormally activated T cells and antigen-presenting cells. This interplay leads to the production of an array of inflammatory cytokines, apoptotic cells, diverse autoantibodies and immune complexes that in turn activate effector cells and the complement system, leading to tissue injury and damage which are the hallmarks of the clinical manifestations. SLE patients have dysregulation of inflammatory cytokines, chemokines and immune response-related genes, as well as of the genes involved in apoptosis, signal transduction and the cell cycle.

IgM autoantibodies to distinct apoptosis-associated antigens correlate with protection from cardiovascular events and renal disease in patients with SLE

Emerging evidence suggests that there are IgM-autoantibodies that may play protective roles in SLE. While IgM are often considered polyreactive, we postulate that there are distinct sets of IgM-autoantibodies of defined autoreactive specificities relevant to different features of SLE. We examined the relationships between levels of IgM natural autoantibodies (NAbs) to apoptosis-associated phosphorylcholine (PC) or malondialdehyde (MDA) antigens, with lupus-associated autoantibodies and features of disease, in 120 SLE patients. IgM anti-PC was significantly higher in patients with low disease activity and less organ damage determined by the SELENA-SLEDAI, the physician's evaluation and the SLICC damage score. Furthermore, IgM anti-PC was significantly higher in patients without cardiovascular events. In contrast, IgM anti-cardiolipin and IgM anti-dsDNA were significantly higher in patients without renal disease. These results support the hypothesis that some IgM autoantibodies are part of a natural immune repertoire that provide homeostatic functions and protection from certain clinical lupus features.

Peroxynitrite-induced modification of H2A histone presents epitopes which are strongly bound by human anti-DNA autoantibodies: role of peroxynitrite-modified-H2A in SLE induction and progression

Peroxynitrite is a potent oxidant and nitrating agent and has in vivo existence. It is a powerful proinflammatory substance and may increase vascular permeability in inflamed tissues. Systemic lupus erythematosus (SLE) is an autoimmune inflammatory disease of unknown etiology. Since its discovery, numerous self- and non-self, nuclear, and cytoplasmic antigens have been suggested as stimuli for SLE initiation, but the exact trigger is yet to be identified. In this study, an attempt has been made to investigate the binding characteristics of SLE anti-DNA autoantibodies to native DNA and native and peroxynitrite-modified H2A histone to explore the possible role of modified protein antigen(s) in SLE initiation and progression. The nuclear protein (H2A histone) was modified by peroxynitrite synthesized in our laboratory. The peroxynitrite-modified H2A revealed generation of nitrotyrosine, dityrosine, and carbonyls when subjected to investigation by physicochemical methods. Binding characteristics and specificity of SLE anti-DNA antibodies were analyzed by direct binding and inhibition enzyme-linked immunosorbent assay. The data show preferential binding of SLE autoantibodies to peroxynitrite-modified H2A histone in comparison with native H2A histone or native DNA. A band shift assay further substantiated the enhanced recognition of peroxynitirite-modified H2A histone by anti-DNA autoantibodies. The results suggest that peroxynitrite modification of self-antigen(s) can generate neoepitopes capable of inducing SLE characteristic autoantibodies. The preferential binding of peroxynitrite-modified H2A histone by SLE anti-DNA antibodies points out the likely role of oxidatively modified and nitrated H2A histone in the initiation/progression of SLE. Moreover, oxidatively modified and nitrated nuclear protein antigen, rather than nucleic acid antigens, appear to be more suitable as a trigger for SLE.

Implications of the parent-into-F1 model for human lupus pathogenesis: roles for cytotoxic T lymphocytes and viral pathogens

PURPOSE OF REVIEW

The central role of CD4 T cells in lupus pathogenesis is well recognized; however, the mechanism by which CD4 T cells lose tolerance and promote humoral autoimmunity remains unclear. This review examines mechanisms elucidated in the parent-into-F1 model of lupus and their possible parallels in human lupus pathogenesis.

RECENT FINDINGS

In the parent-into-F1 model, lupus results from the transfer of normal, foreign reactive CD4 T cells targeted to intrinsically normal F1 B cells. Transfer of normal CD8 T cells prevents lupus, whereas transfer of CD8 T cells with killing defects does not but is correctable with additional in-vivo enhancement of CD8 cytotoxic T lymphocyte (CTL) function. The parent-into-F1 model has two major similarities to Epstein-Barr virus infection: CD4 T-cell-driven polyclonal B-cell hyperactivity and a critical dependence on CD8 CTL for elimination of activated B cells. These similarities are discussed in relation to human lupus pathogenesis.

SUMMARY

Work in the parent-into-F1 model supports the idea that lupus may result from defective CD8 T-cell function and that therapeutic enhancement of CD8 effectors with selective targeting to autoreactive B cells may be beneficial. Despite strong evidence linking Epstein-Barr virus infection with human lupus, the exact nature of this link requires further study.

(S)-armepavine from Chinese medicine improves experimental autoimmune crescentic glomerulonephritis

OBJECTIVE

Intra-renal T cells and macrophages play a key pathogenic role in the development and progression of glomerular crescents. We aimed to establish (S)-armepavine [(S)-ARM], a major bioactive compound of a Chinese medicinal plant, Nelumbo nucifera, as a potential therapeutic agent in the treatment of autoimmune crescentic glomerulonephritis (ACGN).

METHODS

A mouse ACGN model associated with T-cell dysregulation, was used to evaluate the therapeutic effects of (S)-ARM on the rapidly progressive glomerular disorder.

RESULTS

The results showed that (S)-ARM administered in the established phase of ACGN is capable of dramatically decreasing glomerular crescents in the kidney and improving proteinuria and renal dysfunction. These effects were associated with greatly inhibited infiltration of T cells/macrophages and suppressed nuclear factor (NF)-κB activation in the kidney, lowered serum levels of autoantibodies and both serum and intra-renal levels of pro-inflammatory cytokines, suppressed T/B-cell activation and T-cell proliferation of the spleen, reduced glomerular immune deposits and apoptosis in both the spleen and kidney in (S)-ARM-treated ACGN mice, compared with the vehicle-treated (disease control) group of ACGN mice.

CONCLUSION

We demonstrated therapeutic effects of (S)-ARM on ACGN as a result of: (i) early systemic negative modulation of T/B cells; (ii) intra-renal regulation of combined NF-κB activation and mononuclear leucocytic infiltration, thereby preventing glomerular crescent formation; and (iii) protection from apoptosis in both the spleen and kidney.

Donor CD8 T cell activation is critical for greater renal disease severity in female chronic graft-vs.-host mice and is associated with increased splenic ICOS(hi) host CD4 T cells and IL-21 expression

Lupus-like renal disease in DBA/2-into-F1 (DBA --> F1) mice is driven by donor CD4 T cells and is more severe in females. Donor CD8 T cells have no known role. As expected, we observed that females receiving unfractionated DBA splenocytes (CD8 intact --> F1) exhibited greater clinical and histological severities of renal disease at 13 weeks compared to males. Surprisingly, sex-based differences in renal disease severity were lost in CD8 depleted --> F1 mice due to an improvement in females and a worsening in males. CD8 intact --> F1 female mice exhibited significantly greater donor and host effector (CD44(hi), CD62L(lo)) CD4 T cells and ICOS(hi) CD4 T follicular helper cells than males. CD8 depleted --> F1 female mice exhibited a reduction in the absolute numbers of host, but not donor CD4 Tfh cells and lost the significant increase in host CD4 effector cells vs. males. Greater female IL-21 expression, a product of Tfh cells, was seen in CD8 intact --> F1 and although reduced was still greater than male CD8 depleted --> F1 mice. Thus, donor CD8 T cells have a critical role in mediating sex-based differences in lupus renal disease severity possibly through greater host ICOS(hi) CD4 T cell involvement.

The MHC haplotype H2b converts two pure nonlupus mouse strains to producers of antinuclear antibodies

Studies of mouse lupus models have linked the MHC H2(b) haplotype with the earlier appearance of antinuclear autoantibodies and the worsening of nephritis. However, it is unknown whether H2(b) by itself, in the context of pure nonlupus strains, is "silent" or sufficient with regard to loss of tolerance to chromatin (nucleosomes). In this study we show that, beginning approximately 6-9 mo of age, H2(b)-congenic BALB/c (denoted BALB.B) mice, unlike BALB/c (H2(d)) and H2(k)-congenic BALB/c (denoted BALB.K) mice, develop strikingly increased serum levels of anti-chromatin Ab dominated by the IgG2a subclass, along with minor increase of Abs to DNA and moderately increased total serum IgG2a. The BALB.B mice did not have glomerulonephritis or an increased mortality rate. H2(b)-congenic C3H/He mice (designated C3.SW mice), unlike C3H/He (H2(k)) mice, showed low but measurable serum levels of chromatin-reactive IgG2a Abs and minor but significant hypergammaglobulinemia. By immunofluorescence, IgG2a of sera from both H2(b)-congenic strains stained HEp-2 cell nuclei, confirming the presence of antinuclear autoantibodies. Thus, in the context of two pure nonlupus genomes, the MHC H2(b) haplotype in homozygous form is sufficient to induce loss of tolerance to chromatin.

Defective B-cell response to T-dependent immunization in lupus-prone mice

Lupus anti-nuclear Ab show the characteristics of Ag-driven T-cell-dependent (TD) humoral responses. If autoAg elicit the same response as exogenous Ag, lupus should enhance humoral responses to immunization. Blunted responses to various immunizations have, however, been reported in a significant portion of lupus patients. In this study, we show that lupus-prone C57BL/6.Sle1.Sle2.Sle3 (B6.TC) mice produce significantly less Ab in response to TD immunization than congenic controls, while producing significantly more total Ig. This blunted Ab response to TD Ag could be reconstituted with B6.TC B and CD4+ T cells. Multiple defects were found in the B6.TC response to 4-hydroxy-3-nitrophenylacetyl-keyhole limpet hemocyanin (NP-KLH) compared with total Ig, including a smaller percentage of B cells participating in the NP-response, a reduced entry into germinal centers, and highly defective production of NP-specific long-lived plasma cells (PC) in the bone marrow. B6.TC PC expressed reduced levels of FcgammaRIIb, which suggests that reduced apoptosis in resident PC prevents the establishment of newly formed NP-specific PC in bone marrow niches. Overall, these results show that lupus-prone mice responded differently to auto- and exogenous Ag and suggest that low FcgammaRIIb, hypergammaglobulinemia, and high autoAb production would be predictive of a poor response to immunization in lupus patients.

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.

The antichromatin antibodies can be useful as a diagnostic tool and disease activity marker of systemic lupus erythematosus in Koreans

We have investigated the clinical utility of antichromatin antibodies for the diagnosis of SLE and as a marker of disease activity in Korean SLE patients. Blood samples were collected from SLE patients, lupus syndrome patients having only two or three of ACR classification criteria for SLE and normal controls. The level of antichromatin antibody was measured by enzyme linked immunosorbent assay and expressed as arbitrary unit. The antichromatin antibody levels of the SLE and lupus syndrome patients were higher than NC. The antichromatin antibody levels were significant higher in SLE patients with arthritis. A significant correlation was found between the level of antichromatin antibodies and each of anti-dsDNA antibody, leukopenia, complement and SLEDAI. The change of antichromatin antibody levels showed a positive correlation with the change of SLEDAI in serial samples. These data suggest that the antichromatin antibodies appear to be a useful laboratory test that can help in the diagnosis and assessment of SLE.

Antinucleosome antibodies in primary antiphospholipid syndrome: a hint at systemic autoimmunity?

BACKGROUND

Antinucleosome antibodies (anti-NCS) are reported to be highly sensitive and specific for systemic lupus erythematosus (SLE) and to correlate with disease activity. They may appear in early stages of the disease, in particular before anti-dsDNA antibodies, being a potential marker for identifying patients susceptible to SLE. Patients with primary antiphospholipid syndrome (PAPS) may develop full-blown SLE but there is no evidence for markers predictive for that.

AIM

To evaluate whether anti-NCS may be predictors for full-blown or lupus like disease (LL) in a cohort of PAPS patients.

METHODS

A multicentric cohort of 105 PAPS patients was tested for IgG/IgM anti-NCS by using a home made assay with H1-stripped chromatin as antigen.

RESULTS

Eighty-one out of 105 (77%) of the patients were positive for anti-NCS; medium-high titre results were present only in 49/105 (46%). Anti-NCS were more frequently detected in PAPS+LL, but no relationship with clinical/serological features was found, except for a weak correlation with anti-dsDNA antibodies. Two PAPS patients evolved into full-blown SLE during the follow-up and displayed high titre anti-NCS many years before.

CONCLUSIONS

Our findings suggest that anti-NCS might be added to the mosaic of autoimmune phenomena characterizing PAPS patients and in particular those with more chance to evolve to SLE.

Epstein-Barr virus and molecular mimicry in systemic lupus erythematosus

Systemic lupus erythematosus (SLE or lupus) is a complex disease with a multifactoral etiology, with genetic, hormonal, and environmental influences. Molecular mimicry as a result of viral infection may contribute to the development of lupus. The pattern of autoantibody development in lupus is consistent with initiation through molecular mimicry, as the initial autoantigenic epitopes that have been observed are limited and cross-reactive with viral proteins. Autoantibody specificity may then later diversify to other autoantigens through B-cell epitope spreading. Epstein-Barr virus (EBV) is an excellent candidate to be involved in molecular mimicry in lupus. EBV infection has been associated with lupus through serological and DNA studies. Infection with EBV results in the production of the viral protein Epstein-Barr virus nuclear antigen-1 (EBNA-1), antibodies against which cross-react with lupus-associated autoantigens, including Ro, Sm B/B', and Sm D1, in lupus patients. The immune response against EBV, and EBNA-1 in particular, differs among lupus patients and healthy controls, with controls maintaining a limited humoral response and failing to produce long-standing cross-reactive antibodies. We hypothesize that the humoral immune response to EBNA-1 in susceptible individuals leads to the generation of cross-reactive antibodies. Through the process of epitope spreading, these cross-reactive antibodies target additional, non-cross reactive autoepitopes, spread to additional autoantigens, and become pathogenic, leading eventually to clinical lupus. This paper reviews some of the current literature supporting roles for EBV exposure and epitope spreading in SLE.

Decoy receptor 3 ameliorates an autoimmune crescentic glomerulonephritis model in mice

Autoimmune crescentic glomerulonephritis (ACGN) is a variant of crescentic glomerulonephritis. The outcome of treatment of crescentic glomerulonephritis is poor. Binding of decoy receptor 3 (DCR3) to its ligand is capable of downregulating the alloresponsiveness of T cells. DCR3 has also been shown to benefit an experimental autoimmune model of diabetes. This study tested the hypothesis that a potential immune regulator, DCR3, could prevent the evolution of ACGN. With the use of an established ACGN model in mice, mice were treated with 100 microg/10 g body wt human DCR3 by hydrodynamics-based gene delivery at 14-d intervals. The results showed that the gene therapy resulted in (1) suppression of T and B cell activation and T cell proliferation; (2) a reduction in serum levels of proinflammatory cytokines; (3) improvement of proteinuria and renal dysfunction; (4) prevention of glomerular crescent formation, renal interstitial inflammation, and glomerulosclerosis; (5) a reduction in serum levels of autoantibodies and glomerular immune deposits; (6) inhibition of apoptosis in the spleen and kidney; (7) prevention of T cell and macrophage infiltration of the kidney; and (8) suppression of fibrosis-related gene expression in the kidney compared with empty vector-treated (disease control) ACGN mice. On the basis of these findings, it is proposed that human DCR3 exerts its preventive and protective effects on ACGN through modulation of T cell activation/proliferation, B cell activation, protection against apoptosis, and suppression of mononuclear leukocyte infiltration in the kidney.

Characterization of reciprocal Lmb1-4 interval MRL-Faslpr and C57BL/6-Faslpr congenic mice reveals significant effects from Lmb3

Susceptibility to severe lupus in MRL-Fas(lpr) mice requires not only the lpr mutation but also other predisposing genes. Using (MRL-Fas(lpr) x B6-Fas(lpr))F2 (where B6 represents C57BL/6) intercrosses that utilize the highly susceptible MRL and poorly susceptible B6 backgrounds, we previously mapped CFA-enhanced systemic lupus-like autoimmunity to four loci, named Lmb1-4, on chromosomes 4, 5, 7, and 10. In the current study, we generated and analyzed reciprocal interval congenic mice for susceptibility to CFA-enhanced autoimmunity at all four Lmb loci. Although all loci had at least a slight effect on lymphoproliferation, only Lmb3 demonstrated a major effect on lymphoproliferation and anti-chromatin Ab levels. Further characterization of Lmb3, primarily by comparing MRL-Fas(lpr) with MRL.B6-Lmb3 Fas(lpr) congenic mice, revealed that it also played a significant role in spontaneous lupus, modifying lymphoproliferation, IgG and autoantibody levels, kidney disease, and survival. The less susceptible B6 Lmb3 locus was associated with a marked reduction in numbers of CD4(+) and double-negative (CD4(-)CD8(-)) T cells, particularly in lymph nodes, as well as reduced T cell proliferation and enhanced T cell apoptosis, both in vivo and in vitro. IFN-gamma-producing CD4(+) T cells were also reduced in MRL.B6-Lmb3 Fas(lpr) mice. Further mapping using subinterval congenic mice placed Lmb3 in the telomeric portion of chromosome 7. Thus, Lmb3, primarily through its effects on CD4(+) and double-negative T cells, appears to be a highly penetrant lupus-modifying locus. Identification of the underlying genetic alteration responsible for this quantitative trait locus should provide new insights into lupus-modifying genes.

Low-dose peptide tolerance therapy of lupus generates plasmacytoid dendritic cells that cause expansion of autoantigen-specific regulatory T cells and contraction of inflammatory Th17 cells

Subnanomolar doses of an unaltered, naturally occurring nucleosomal histone peptide epitope, H4(71-94), when injected s.c. into lupus-prone mice, markedly prolong lifespan by generating CD4+25+ and CD8+ regulatory T cells (Treg) producing TGF-beta. The induced Treg cells suppress nuclear autoantigen-specific Th and B cells and block renal inflammation. Splenic dendritic cells (DC) captured the s.c.-injected H4(71-94) peptide rapidly and expressed a tolerogenic phenotype. The DC of the tolerized animal, especially plasmacytoid DC, produced increased amounts of TGF-beta, but diminished IL-6 on stimulation via the TLR-9 pathway by nucleosome autoantigen and other ligands; and those plasmacytoid DC blocked lupus autoimmune disease by simultaneously inducing autoantigen-specific Treg and suppressing inflammatory Th17 cells that infiltrated the kidneys of untreated lupus mice. Low-dose tolerance with H4(71-94) was effective even though the lupus immune system is spontaneously preprimed to react to the autoepitope. Thus, H4(71-94) peptide tolerance therapy that preferentially targets pathogenic autoimmune cells could spare lupus patients from chronically receiving toxic agents or global immunosuppressants and maintain remission by restoring autoantigen-specific Treg cells.

Hepatocyte growth factor prevents lupus nephritis in a murine lupus model of chronic graft-versus-host disease

Chronic graft-versus-host disease (GVHD) induced in (C57BL/6 x DBA/2) F1 (BDF1) mice by the injection of DBA/2 mouse spleen cells represents histopathological changes associated with systemic lupus erythematosus (SLE), primary biliary cirrhosis (PBC) and Sjogren's syndrome (SS), as indicated by glomerulonephritis, lymphocyte infiltration into the periportal area of the liver and salivary glands. We determined the therapeutic effect of hepatocyte growth factor (HGF) gene transfection on lupus using this chronic GVHD model. Chronic GVHD mice were injected in the gluteal muscle with either HVJ liposomes containing 8 microg of the human HGF expression vector (HGF-HVJ liposomes) or mock vector (untreated control). Gene transfer was repeated at 2-week intervals during 12 weeks. HGF gene transfection effectively prevented the proteinuria and histopathological changes associated with glomerulonephritis. While liver and salivary gland sections from untreated GVHD mice showed prominent PBC- and SS-like changes, HGF gene transfection reduced these histopathological changes. HGF gene transfection greatly reduced the number of splenic B cells, host B cell major histocompatibility complex class II expression, and serum levels of IgG and anti-DNA antibodies. IL-4 mRNA expression in the spleen, liver, and kidneys was significantly decreased by HGF gene transfection. CD28 expression on DBA/2 CD4+ T cells was decreased by the addition of recombinant HGF in vitro. Furthermore, IL-4 production by DBA/2 CD4+ T cells stimulated by irradiated BDF1 dendritic cells was significantly inhibited by the addition of recombinant HGF in vitro. These results suggest that HGF gene transfection inhibited T helper 2 immune responses and reduced lupus nephritis, autoimmune sialoadenitis, and cholangitis in chronic GVHD mice. HGF may represent a novel strategy for the treatment of SLE, SS and PBC.

Role of anti-nucleosome antibody in the diagnosis of systemic lupus erythematosus

OBJECTIVE

To investigate the role of anti-nucleosome antibodies (AnuA) in systemic lupus erythematosus (SLE).

METHODS

IgG anti-nucleosome antibodies were detected by enzyme-linked immunosorbent assay (ELISA) in the sera of 233 SLE and 220 other rheumatic diseases' patients as well as 31 health controls. The patients were also evaluated for clinical and biological parameters.

RESULTS

(1) Out of 233 SLE patients, 144 (61.8%) were seropositive for AnuA, which was significantly higher than that of patients with other rheumatic diseases [2.7% (6/220), P < 0.001]; the sensitivities and specificities of AnuA in SLE were 61.8% and 97.6%, respectively. (2) The positive rated of AnuA in SLE lacking of anti-DNP, anti-cmDNA, anti-Sm and anti-dsDNA antibodies were 57.1%, 55.9%, 62.4% and 51.2%, respectively. (3) The frequency of the fever, skin rash, and arthralgia were significantly higher in 144 positive AnuA SLE than those in AnuA negative SLE (P < 0.05). The frequency of leukopenia, elevations of ESR and CRP, lower C3/C4 levels and proteinuria in AnuA positive groups was significantly higher than that of AnuA negative groups (P < 0.05). (4) Level of AnuA was strongly correlated with the SLEDAI scores (r = 0.385, P < 0.001). Patients with active SLE showed significantly higher positive rate of AnuA (66.1%) than those with inactive disease (45.7%) (chi2 = 6.568, P = 0.010).

CONCLUSIONS

AnuA is one of the most valuable markers in the diagnosis of SLE lacking of anti-dsDNA, anti-Sm, anti-DNP and anti-cmDNA antibodies. The level of AnuA is associated with the disease activity of SLE.

Divergent members of a single autoreactive B cell clone retain specificity for apoptotic blebs

Specificity for double-stranded DNA can arise due to somatic mutations within one of the branches of an autoreactive B cell clone. However, it is not known whether a different autospecificity predates anti-dsDNA and whether separate offshoots of an expanding B cell clone retain or evolve alternative specificities. We compared 3H9, an anti-dsDNA IgG, to 4H8 and 1A11, antibodies produced by hybridomas representing an alternative branch of the 3H9 B cell clone. All three IgG bound chromatin in ELISA and apoptotic cells in confocal microscopy, yet only 3H9 bound dsDNA, as measured by plasmon resonance. Moreover, we demonstrate that despite the unique specificity of 3H9 for dsDNA, all three clone members exhibited indistinguishable binding to chromatin. The binding to chromatin and apoptotic cells was unaffected by N-linked glycosylation in L chain CDR1, a modification that results from a replacement of serine 26 with asparagine in 4H8 and 1A11. These data provide the first evidence that specificity for nucleosome epitopes on apoptotic cells provides the initial positive stimulus for somatic variants that comprise a B cell clone, including those that subsequently acquire specificity for dsDNA. Conversely, selection of autoreactive B cells for binding to apoptotic cells leads to clonal expansion, antibody diversification, and the development of linked sets of anti-nuclear autoantibodies.

Antinucleosome antibodies correlate with the disease severity in children with systemic lupus erythematosus

We compared the serum levels of antinucleosome antibodies (anti-NCS Abs) in thirty pediatric systemic lupus erythematosus (SLE) patients by using enzyme-linked immunosorbent assay (ELISA) to 29 adult SLE patients, 30 healthy controls, 21 juvenile idiopathic arthritis (JIA) and 23 Henoch-Schonlein purpura (HSP) patients as autoimmune disease controls. The mean anti-NCS Ab titer in the pediatric SLE patients was 1552.7+/-1842.2 U/ml, higher than those of adult SLE patients (194.3+/-402.7 U/ml), normal controls (9.5+/-5.7 U/ml) and disease controls (JIA: 7.7+/-4.0 U/ml, HSP: 5.7+/-4.4 U/ml) (p<0.05). The prevalence of both anti-NCS Ab (90%) and anti-ds DNA Ab (76.7%) in pediatric SLE patients were higher (p<0.05) than that of adult SLE patients (58.6% and 48.3%). A positive correlation was demonstrated between anti-NCS Ab and anti-dsDNA Ab as well as the SLEDAI scores in pediatric and adult patients (p<0.05). The inverse correlation of anti-NCS Ab levels with C3 was observed in both pediatric and adult SLE patients (pediatrics, r=-0.61, p=0.0003; adult, r=-0.44, p=0.02). Our data suggested that in pediatric SLE patients, anti-NCS Ab could be as good a marker for SLE diagnosis and disease activity assessment as in adult SLE patients.

Accumulation of apoptotic cells in the epidermis of patients with cutaneous lupus erythematosus after ultraviolet irradiation

OBJECTIVE

To examine whether apoptosis contributes to the pathogenesis of skin lesions in patients with cutaneous lupus erythematosus (CLE) after ultraviolet (UV) irradiation.

METHODS

In situ nick translation and TUNEL were performed to detect apoptosis in 85 skin biopsy specimens from patients with various subtypes of CLE. Specimens from normal healthy donors and patients with polymorphous light eruption were used as controls. In addition to assessment of primary lesions, provocative phototesting was carried out to investigate events occurring secondary to UV irradiation during a very early stage of lesion formation.

RESULTS

A significant increase in apoptotic nuclei was found in the upper epidermal layer of primary and UV light-induced skin lesions of CLE patients compared with controls. In tissue sections obtained from control subjects at 24 hours after a single exposure to UV light, a slight increase in the count of epidermal apoptotic nuclei was present as compared with skin tissue from CLE patients obtained under the same conditions before lesion formation. In sections obtained from controls at 72 hours after irradiation, a significant decrease in the apoptotic nuclei count was observed, consistent with a proper clearance of apoptotic cells in the period between 24 and 72 hours after irradiation. In striking contrast, the number of apoptotic nuclei increased significantly within this period in tissue sections from patients with CLE.

CONCLUSION

These data support the hypothesis that apoptotic cells accumulate in the skin of patients with CLE after UV irradiation, as a result of impaired or delayed clearance. The nonengulfed cells may undergo secondary necrosis and release proinflammatory compounds and potential autoantigens, which may contribute to the inflammatory micromilieu that leads to formation of skin lesions in this disease.

The in vivo expression of actin/salt-resistant hyperactive DNase I inhibits the development of anti-ssDNA and anti-histone autoantibodies in a murine model of systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is characterised by the production of autoantibodies against ubiquitous antigens, especially nuclear components. Evidence makes it clear that the development of these autoantibodies is an antigen-driven process and that immune complexes involving DNA-containing antigens play a key role in the disease process. In rodents, DNase I is the major endonuclease present in saliva, urine and plasma, where it catalyses the hydrolysis of DNA, and impaired DNase function has been implicated in the pathogenesis of SLE. In this study we have evaluated the effects of transgenic over-expression of murine DNase I endonucleases in vivo in a mouse model of lupus. We generated transgenic mice having T-cells that express either wild-type DNase I (wt.DNase I) or a mutant DNase I (ash.DNase I), engineered for three new properties – resistance to inhibition by G-actin, resistance to inhibition by physiological saline and hyperactivity compared to wild type. By crossing these transgenic mice with a murine strain that develops SLE we found that, compared to control non-transgenic littermates or wt.DNase I transgenic mice, the ash.DNase I mutant provided significant protection from the development of anti-single-stranded DNA and anti-histone antibodies, but not of renal disease. In summary, this is the first study in vivo to directly test the effects of long-term increased expression of DNase I on the development of SLE. Our results are in line with previous reports on the possible clinical benefits of recombinant DNase I treatment in SLE, and extend them further to the use of engineered DNase I variants with increased activity and resistance to physiological inhibitors.

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.

The regulation and activation of lupus-associated B cells

Anti-double-stranded DNA (anti-dsDNA) B cells are regulated in non-autoimmune mice. While some are deleted or undergo receptor editing, a population of anti-dsDNA (VH3H9/V lambda 1) B cells that emigrate into the periphery has also been identified. These cells have an altered phenotype relative to normal B cells in that they have a reduced lifespan, appear developmentally arrested, and localize primarily to the T/B-cell interface in the spleen. This phenotype may be the consequence of immature B cells encountering antigen in the absence of T-cell help. When provided with T-cell help, the anti-dsDNA B cells differentiate into antibody-forming cells. In the context of the autoimmune-prone lpr/lpr or gld/gld mutations, the VH3H9/V lambda 1 anti-dsDNA B cells populate the B-cell follicle and by 12 weeks of age produce serum autoantibodies. The early event of anti-dsDNA B-cell follicular entry, in the absence of autoantibody production, is dependent upon CD4(+) T cells. We hypothesize that control of autoantibody production in young autoimmune-prone mice may be regulated by the counterbalancing effect of T-regulatory (T(reg)) cells. Consistent with this model, we have demonstrated that T(reg) cells are able to prevent autoantibody production induced by T-cell help. Additional studies are aimed at investigating the mechanisms of this suppression as well as probing the impact of distinct forms of T-cell-dependent and -independent activation on anti-dsDNA B cells.

Autoimmune alterations induced by the New Zealand Black Lbw2 locus in BWF1 mice

The New Zealand Black (NZB) Lbw2 locus (lupus NZB x New Zealand White (NZW) 2 locus) was previously linked to mortality and glomerulonephritis, but not to IgG autoantibodies, suggesting that it played a role in a later disease stage. To define its contribution, (NZB x NZW)F1 hybrids (BWF1) containing two, one, or no copies of this locus were generated. Lack of the NZB Lbw2 indeed reduced mortality and glomerulonephritis, but not serum levels of total and anti-DNA IgG Abs. There were, however, significant reductions in the B cell response to LPS, total and anti-DNA IgM and IgG Ab-forming cells, IgM Ab levels, and glomerular Ig deposits. Furthermore, although serum IgG autoantibody levels correlated poorly with kidney IgG deposits, the number of spontaneous IgG Ab-forming cells had a significant correlation. Genome-wide mapping of IgM anti-chromatin levels identified only Lbw2, and analysis of subinterval congenics tentatively reduced Lbw2 to approximately 5 Mb. Because no known genes associated with B cell activation and lupus are in this interval, Lbw2 probably represents a novel B cell activation gene. These findings establish the importance of Lbw2 in the BWF1 hybrid and indicate that Lbw2, by enhancing B cell hyperactivity, promotes the early polyclonal activation of B cells and subsequent production of autoantibodies.

Ongoing immunoglobulin class switch DNA recombination in lupus B cells: analysis of switch regulatory regions

Inflammation and tissue damage in systemic lupus erythematosus (SLE) are mediated by class-switched autoantibodies reactive with nucleic acids, nucleic acid-binding proteins, phospholipids and other self-antigens. While some healthy individuals produce IgM antibodies with specificities similar to those of lupus patients, immunoglobulin class switching to mature downstream isotypes appears to be required for the generation of pathogenic autoantibodies. To characterize the cellular and molecular basis of pathogenic autoantibody production in SLE, we studied the capacity of peripheral blood B cells of naive phenotype from patients with SLE, rheumatoid arthritis (RA) or healthy control subjects to spontaneously switch to IgG and IgA. In addition, we determined the DNA sequences of the upstream evolutionary conserved sequence (ECS)-Igamma promoter regulatory regions that control germline IH-CH transcription and class switch DNA recombination (CSR) to IgG1, IgG2 and IgG4. IgM+IgD+ B cells from patients with SLE, but not those from RA or healthy control subjects, underwent spontaneous CSR, as assessed by expression of germline Igamma1-Cgamma1, Igamma2-Cgamma2, Igamma3-Cgamma3, Igamma4-Cgamma4 and Ialpha1-Calpha1 transcripts, mature (switched) VHDJH-Cgamma1, VHDJH-Cgamma2, VHDJH-Cgamma3 and VHDJH-Calpha1 transcripts and secreted IgG and IgA. Although polymorphic DNA sequences were identified in the ECS-Igamma1, ECS-Igamma2 and ECS-Igamma4 promoter regions, the transcription factor-binding sites that mediate germline Igamma-Cgamma transcription were conserved in patients and controls. However, distinct patterns of nuclear protein binding to an ECS-Igamma promoter sequence that contains both positive and negative regulatory elements were observed in SLE patients and controls. These results support a role for exogenous signals, such as through CD40 ligation, rather than altered genomic sequence, in the increased production of class switched autoantibodies in SLE.

Mature dendritic cells readily break tolerance in normal mice but do not lead to disease expression

OBJECTIVE

To examine the ability of mature dendritic cells (DCs) or macrophages intentionally exposed to lipopolysaccharide or apoptotic or necrotic cells to break tolerance in normal mice.

METHODS

We adoptively transferred into C57BL/6 mice a variety of syngeneic myeloid antigen-presenting cell populations exposed to different activation stimuli as well as to meals of necrotic and apoptotic cells. We studied expression of autoimmunity in the immunized mice by serologic evaluation of autoantibody production, subclass analysis of Ig production, clinical evidence of kidney disease, glomerular immune complex deposition, and renal pathology.

RESULTS

Injection of mice with DCs incubated with apoptotic or necrotic cells, as well as, surprisingly, with DCs cultured in media alone, induced high levels of IgG autoantibodies, including anti-double-stranded DNA (anti-dsDNA) antibodies. In striking contrast, transfer of equivalent-treated macrophages failed to generate IgG autoantibodies. IgG was deposited in the kidneys of mice vaccinated with DCs, but despite high levels of anti-dsDNA antibodies, these mice did not develop overt nephritis. Serologic evaluation of the antibody response revealed that the mice primarily developed elevated levels of IgG1 antibodies, including high levels of IgG1 anti-dsDNA.

CONCLUSION

The data suggest that mature myeloid DCs are able to break tolerance and induce lupus autoantibodies in normal hosts, but that other susceptibility factors must be in place to induce long-lasting autoimmunity and clinical expression of disease.

Autoantibodies in SLE but not in scleroderma react with protein-stripped nucleosomes

Autoantibodies against nucleosomes (ANuA) are known to be sensitive markers for systemic lupus erythematosus (SLE), but their clinical relevance seemed to be limited because sera from patients with progressive systemic sclerosis (PSS) also showed positive reactions with conventional ANuA ELISA test systems (anti-Nu1 ELISA). It was generally assumed thatANuA were associated with both diseases. Using discontinuous sucrose gradient centrifugation to generate pure nucleosomes, we discovered by chance that at the 30-50% sucrose interface an antigen (Nu2) banded which was demonstrably free of non-histone components and histone H1. The two different nucleosome preparations, Nu1 and Nu2, were used in parallel as antigenic substrates in standardised ELISA tests to analyse sera from SLE (295 patients), PSS (119) and patients with other rheumatic diseases (101). With Nu1, 62% of the SLE and 52% of the PSS sera showed positive reactions. Two sera from patients suffering from Sjögren's syndrome (SS) and one from polymyositis were also positive. Using the Nu2 preparation, 58% of the SLE but none of the PSS sera showed a positive reaction. One serum from a patient with SS was also positive. It could be shown that it was the PSS-specific autoantigen Scl-70 in the nucleosome preparation (Nu1) which contributed to the positive reactions of the PSS sera in conventional ANuA test systems, whereas in the Nu2 preparation no remaining Scl-70 was detectable. The present study definitely proved that ANuA are highly and specifically associated with SLE but not with PSS.

Antinucleosome antibody is a major autoantibody in localized scleroderma

BACKGROUND

Localized scleroderma (LSc) exhibits autoimmunity, and antihistone antibody is frequently detected. The major antigens recognized by antihistone antibody are histones H1, H2A and H2B, which are located on the outer side of the nucleosome and are relatively more accessible for antibody binding. Therefore, it has been hypothesized that antihistone antibody is induced by nucleosome or native chromatin as immunogens in LSc.

OBJECTIVES

To determine whether antinucleosome antibody is present in patients with LSc.

METHODS

Antinucleosome antibody, antihistone antibody and antidouble-stranded DNA (dsDNA) antibody were determined by enzyme-linked immunosorbent assay. Results IgG or IgM antinucleosome antibody was detected more frequently in patients with LSc than was antihistone antibody: in 40 of 49 (82%) vs. 26 of 49 (53%), respectively. No patients had anti-dsDNA antibody. The prevalence of antinucleosome antibody positivity was comparable in the three subgroups of LSc (generalized morphoea, 89%; linear scleroderma, 71%; morphoea, 90%). Patients with systemic lupus erythematosus (SLE) exhibited a similar frequency of antinucleosome antibody positivity (13 of 15, 87%), but their IgG levels of this autoantibody were much higher than those found in patients with LSc. By contrast, IgM antinucleosome antibody levels were normal in patients with SLE, while they were significantly increased in patients with LSc compared with normal controls. Antinucleosome antibody was also detected at lower frequency in patients with systemic sclerosis (five of 20, 25%) or dermatomyositis (five of 15, 33%). Nucleosome-restricted antibodies, i.e. antibodies that react with the whole nucleosome particle but not with its individual components (histones and dsDNA) were also present in 35% of patients with LSc.

CONCLUSIONS

Although antinucleosome antibody was not specific to LSc, its high prevalence in LSc indicates that antinucleosome antibody is a major autoantibody in this disease.

The effect of the phytoestrogen coumestrol on the NZB/W F1 murine model of systemic lupus

Coumestrol is a naturally occurring plant estrogen. As estrogen influences cellular and humoral immunity, and has known effects on murine models of lupus, we investigated the effect of coumestrol on disease expression in the NZB/W F1 mouse. Female NZB/W F1 mice were fed a "standard" rodent diet including soy proteins, a non-soy diet, or a non-soy diet with 0.01% coumestrol. Outcome measures included survival, autoantibody expression, immunoglobulin levels, proteinuria, renal histology and B cell immunohistochemistry, and renal mRNA expression. At 24 weeks, the treatment group had decreased prevalence of autoantibodies detected by immunofluorescence and less splenomegaly. At 39 weeks, the prevalence of autoantibodies was similar but the treatment group had less proteinuria. Overall, there was little effect of treatment on renal mRNA levels as assessed by gene array analysis, but functional ontology mapping revealed that genes encoding proteins involved in the immune response were most often affected. These results suggest that treatment with coumestrol may ameliorate some aspects of disease progression in this model of systemic autoimmunity.

Clinical significance of antinucleosome antibodies in Tunisian systemic lupus erythematosus patients

The aim of this study was to investigate the clinical significance of antinucleosome antibodies in Tunisian systemic lupus erythematosus (SLE) patients. IgG antinucleosome antibodies were detected by a qualitative enzyme immunoassay (immunodot) in the sera of SLE patients at onset of disease. The patients were divided into two groups according to the result of the antinucleosome antibodies test: positive (group A) and negative (group B). The two groups were also evaluated for clinical and biological parameters. Of 84 patients with SLE, 66 (78.6%) had antinucleosome antibodies. Among 21 patients negative for anti-double-stranded DNA (anti-dsDNA), 5 (23.8%) were antinucleosome positive. The most common initial features were haematological disorders (80.1%) and arthritis or arthralgias (79.8%). Renal disorders, observed in 59.5% of SLE patients, were more common in group A compared to group B (65 vs 38%) (p=0.04). The European Consensus Lupus Activity Measurement (ECLAM) mean score was higher in group A (6.42) than in group B (4.44) (p=0.002). Antinucleosome antibodies were positive in nearly one-fourth of SLE patients negative for anti-dsDNA. We found a correlation between antinucleosome antibodies, nephritis and SLE disease activity. Therefore, the determination of circulating antinucleosome antibodies could be a useful parameter for early diagnosis and follow-up of SLE patients.

Nucleosome-specific regulatory T cells engineered by triple gene transfer suppress a systemic autoimmune disease

The mechanisms of systemic autoimmune disease are poorly understood and available therapies often lead to immunosuppressive conditions. We describe here a new model of autoantigen-specific immunotherapy based on the sites of autoantigen presentation in systemic autoimmune disease. Nucleosomes are one of the well-characterized autoantigens. We found relative splenic localization of the stimulative capacity for nucleosome-specific T cells in (NZB x NZW)F(1) (NZB/W F(1)) lupus-prone mice. Splenic dendritic cells (DCs) from NZB/W F(1) mice spontaneously stimulate nucleosome-specific T cells to a much greater degree than both DCs from normal mice and DCs from the lymph nodes of NZB/W F(1) mice. This leads to a strategy for the local delivery of therapeutic molecules using autoantigen-specific T cells. Nucleosome-specific regulatory T cells engineered by triple gene transfer (TCR-alpha, TCR-beta, and CTLA4Ig) accumulated in the spleen and suppressed the related pathogenic autoantibody production. Nephritis was drastically suppressed without impairing the T cell-dependent humoral immune responses. Thus, autoantigen-specific regulatory T cells engineered by multiple gene transfer is a promising strategy for treating autoimmune diseases.