Antibodies to DNA

The inhibition of anti-DNA binding to DNA by nucleic acid binding polymers

Antibodies to DNA (anti-DNA) are the serological hallmark of systemic lupus erythematosus (SLE) and can mediate disease pathogenesis by the formation of immune complexes. Since blocking immune complex formation can attenuate disease manifestations, the effects of nucleic acid binding polymers (NABPs) on anti-DNA binding in vitro were investigated. The compounds tested included polyamidoamine dendrimer, 1,4-diaminobutane core, generation 3.0 (PAMAM-G3), hexadimethrine bromide, and a β-cylodextrin-containing polycation. As shown with plasma from patients with SLE, NABPs can inhibit anti-DNA antibody binding in ELISA assays. The inhibition was specific since the NABPs did not affect binding to tetanus toxoid or the Sm protein, another lupus autoantigen. Furthermore, the polymers could displace antibody from preformed complexes. Together, these results indicate that NABPs can inhibit the formation of immune complexes and may represent a new approach to treatment.

Autoantibodies and resident renal cells in the pathogenesis of lupus nephritis: getting to know the unknown

Systemic lupus erythematosus is characterized by a breakdown of self-tolerance and production of autoantibodies. Kidney involvement (i.e., lupus nephritis) is both common and severe and can result in permanent damage within the glomerular, vascular, and tubulo-interstitial compartments of the kidney, leading to acute or chronic renal failure. Accumulating evidence shows that anti-dsDNA antibodies play a critical role in the pathogenesis of lupus nephritis through their binding to cell surface proteins of resident kidney cells, thereby triggering the downstream activation of signaling pathways and the release of mediators of inflammation and fibrosis. This paper describes the mechanisms through which autoantibodies interact with resident renal cells and how this interaction plays a part in disease pathogenesis that ultimately leads to structural and functional alterations in lupus nephritis.

Anti-CADM-140/MDA5 autoantibody titer correlates with disease activity and predicts disease outcome in patients with dermatomyositis and rapidly progressive interstitial lung disease

OBJECTIVES

We examined the relationship between disease activity and anti-CADM-140/MDA5 titer measured by enzyme-linked immunosorbent assay (ELISA).

METHODS

Sera from 63 patients with dermatomyositis (DM) [46 classic DM, 17 clinically amyopathic DM (CADM)] were screened for autoantibody using immunoprecipitation assay. Anti-CADM-140/MDA5-positive sera were examined for their titer by anti-CADM-140/MDA5 ELISA. Potential associations between anti-CADM-140/MDA5 titer and clinical course or outcome were analyzed.

RESULTS

Sera from 14 patients with DM (2 classic DM, 12 CADM) had anti-CADM-140/MDA5. Of ten patients with DM and rapidly progressive interstitial lung disease (RP-ILD), the mean titer of anti-CADM-140/MDA5 before treatment was significantly lower in patients who responded to therapy and survived (responder group, n = 4) than in those who did not respond and died (nonresponder group, n = 6) (110.3 vs. 356.9, P = 0.019). In the responder group, the mean titer of anti-CADM-140/MDA5 significantly decreased down to below the cutoff level after treatment (n = 3, 113.4 vs. 1.6, P = 0.033), whereas that of the nonresponder group did not decrease sufficiently and sustained high level (n = 4, 372.5 vs. 198.4, P = 0.31).

CONCLUSIONS

These results emphasize the clinical importance of anti-CADM-140/MDA5 antibody levels to predict outcomes of RP-ILD as well as to monitor disease activity in patients with DM and RP-ILD.

TLR tolerance reduces IFN-alpha production despite plasmacytoid dendritic cell expansion and anti-nuclear antibodies in NZB bicongenic mice

Genetic loci on New Zealand Black (NZB) chromosomes 1 and 13 play a significant role in the development of lupus-like autoimmune disease. We have previously shown that C57BL/6 (B6) congenic mice with homozygous NZB chromosome 1 (B6.NZBc1) or 13 (B6.NZBc13) intervals develop anti-nuclear antibodies and mild glomerulonephritis (GN), together with increased T and B cell activation. Here, we produced B6.NZBc1c13 bicongenic mice with both intervals, and demonstrate several novel phenotypes including: marked plasmacytoid and myeloid dendritic cell expansion, and elevated IgA production. Despite these changes, only minor increases in anti-nuclear antibody production were seen, and the severity of GN was reduced as compared to B6.NZBc1 mice. Although bicongenic mice had increased levels of baff and tnf-α mRNA in their spleens, the levels of IFN-α-induced gene expression were reduced. Splenocytes from bicongenic mice also demonstrated reduced secretion of IFN-α following TLR stimulation in vitro. This reduction was not due to inhibition by TNF-α and IL-10, or regulation by other cellular populations. Because pDC in bicongenic mice are chronically exposed to nuclear antigen-containing immune complexes in vivo, we examined whether repeated stimulation of mouse pDC with TLR ligands leads to impaired IFN-α production, a phenomenon termed TLR tolerance. Bone marrow pDC from both B6 and bicongenic mice demonstrated markedly inhibited secretion of IFN-α following repeated stimulation with a TLR9 ligand. Our findings suggest that the expansion of pDC and production of anti-nuclear antibodies need not be associated with increased IFN-α production and severe kidney disease, revealing additional complexity in the regulation of autoimmunity in systemic lupus erythematosus.

The origin and properties of extracellular DNA: from PAMP to DAMP

DNA is a polymeric macromolecule whose biological activities depend on location as well as binding to associated molecules. Inside the cell, DNA is the source of genetic information and binds histones to form nucleosomes. DNA can exit the cell, however, to enter the extracellular space primarily during cell death, either apoptosis or necrosis, as well as NETosis. While bacterial DNA is a potent immune stimulant by virtue of its CpG motifs, mammalian DNA, which is ordinarily inactive, can acquire activity by associating with nuclear, cytoplasmic and serum proteins which promote its uptake into cells to stimulate internal DNA sensors, including Toll-like receptor 9. Among these proteins, anti-DNA autoantibodies can form immune complexes with DNA to stimulate plasmacytoid dendritic cells to produce type 1 interferon. Together, these findings suggest that the immune properties of DNA are mutable and diverse, reflecting its context and the array of attached molecules.

Increased CD45RA+ FoxP3(low) regulatory T cells with impaired suppressive function in patients with systemic lupus erythematosus

BACKGROUND

The role of naturally occurring regulatory T cells (Treg) in the control of the development of systemic lupus erythematosus (SLE) has not been well defined. Therefore, we dissect the phenotypically heterogeneous CD4(+)FoxP3(+) T cells into subpopulations during the dynamic SLE development. METHODLOGY/PRINCIPAL FINDINGS: To evaluate the proliferative and suppressive capacities of different CD4(+) T cell subgroups between active SLE patients and healthy donors, we employed CD45RA and CD25 as surface markers and carboxyfluorescein diacetatesuccinimidyl ester (CFSE) dilution assay. In addition, multiplex cytokines expression in active SLE patients was assessed using Luminex assay. Here, we showed a significant increase in the frequency of CD45RA(+)FoxP3(low) naive Treg cells (nTreg cells) and CD45RA(-)FoxP3(low) (non-Treg) cells in patients with active SLE. In active SLE patients, the increased proportions of CD45RA(+)FoxP3(low) nTreg cells were positively correlated with the disease based on SLE disease activity index (SLEDAI) and the status of serum anti-dsDNA antibodies. We found that the surface marker combination of CD25(+)CD45RA(+) can be used to defined CD45RA(+)FoxP3(low) nTreg cells for functional assays, wherein nTreg cells from active SLE patients demonstrated defective suppression function. A significant correlation was observed between inflammatory cytokines, such as IL-6, IL-12 and TNFα, and the frequency of nTreg cells. Furthermore, the CD45RA(+)FoxP3(low) nTreg cell subset increased when cultured with SLE serum compared to healthy donor serum, suggesting that the elevated inflammatory cytokines of SLE serum may promote nTreg cell proliferation/expansion.

CONCLUSIONS/SIGNIFICANCE

Our results indicate that impaired numbers of functional CD45RA(+)FoxP3(low) naive Treg cell and CD45RA(-)FoxP3(low) non-suppressive T cell subsets in inflammatory conditions may contribute to SLE development. Therefore, analysis of subsets of FoxP3(+) T cells, using a combination of FoxP3, CD25 and CD45RA, rather than whole FoxP3(+) T cells, will help us to better understand the pathogenesis of SLE and may lead to the development of new therapeutic strategies.

IgG3 deficiency extends lifespan and attenuates progression of glomerulonephritis in MRL/lpr mice

Background

Antibodies of the IgG3 subclass have been implicated in the pathogenesis of the spontaneous glomerulonephritis observed in mice of the MRL/MpJ-Tnfrsf6lpr (MRL/lpr) inbred strain which have been widely studied as a model of systemic lupus erythematosus We have produced IgG3-deficient (-/-) mice with the MRL/lpr genetic background to determine whether IgG3 antibodies are necessary for or at least contributory to MRL/lpr-associated nephritis.

Results

The gamma3 genotype (+/+ vs. +/- vs. -/-) did not appear to significantly affect serum titers of IgG auto-antibodies specific for double-stranded DNA (dsDNA) or α-actinin. However, while substantial serum titers of IgG3 auto-antibodies specific for double-stranded DNA (dsDNA) or α-actinin were seen in gamma3 +/+ mice, somewhat lower serum titers of these IgG3 auto-antibodies were found in gamma3 +/- mice, and gamma3 -/- mice exhibited baseline concentrations of these auto-antibodies. Analysis of immunoglobulins eluted from snap-frozen kidneys obtained from mice of all three gamma3 genotypes at ~18 weeks of age revealed much higher quantities of IgG in the kidneys from gamma3 +/+ than gamma3 -/- mice, and most IgG eluted from +/+ mice was IgG3. The serum creatinine levels in gamma3 +/+ mice substantially exceeded those of age-matched gamma3 -/- mice after ~21 weeks of age. Histopathological examination of kidneys from mice sacrificed at pre-determined ages also revealed more extensive glomerulosclerosis in gamma3 +/+ or +/- mice than in -/- mice beginning at 21 weeks of age. Survival analysis for IgG3-deficient and IgG3-producing MRL/lpr mice revealed that gamma3 -/- mice lived significantly longer (p = 0.0006) than either gamma3 +/- or +/+ mice. Spontaneous death appeared to be due to irreversible renal failure, because > 85% of glomeruli in kidneys from mice that died spontaneously were obliterated by glomerulosclerosis.

Conclusions

The available evidence suggests that IgG3 deficiency partially protects MRL/lpr mice against glomerulonephritis-associated morbidity and mortality by slowing or arresting the progression to glomerulosclerosis.

Reviewers

This article was reviewed by Pushpa Pandiyan, Irun Cohen, and Etienne Joly.

Intracellular inflammatory sensors for foreign invaders and substances of self-origin

In order to survive, all organisms must recognize and eliminate foreign invaders such as infectious pathogens, chemicals, ultraviolet rays, metabolites and damaged or transformed self-tissues, as well as allogenic organs in cases of transplantation. Recent research in innate immunity has elucidated that there are versatile inflammatory sensors on spatiotemporal 'sentry duty' that recognize substances derived from both 'nonself' and 'self', e.g., Toll-like receptors, retinoic acid-inducible gene-I-like receptors, nucleotide oligomerization domain-like receptors and c-type lectin receptors. Having acquired high-level functions through the development of multiple molecules, higher organisms have established both extracellular and intracellular sensors that can discriminate danger-associated molecular patterns from promiscuous, but biologically similar, molecular patterns. In addition, 'loss-of-function' or 'gain-of-function' mutations in these inflammatory sensors have been linked (at least in part) with the etiology and severity of autoimmune diseases, autoinflammatory diseases and immunocompromised diseases in humans. Further studies focusing on the role of these inflammatory sensors in the development of immune disorders would highlight new avenues for the development of novel diagnostic and therapeutic applications with regard to these diseases.

B Cell in Autoimmune Diseases

The role of B cells in autoimmune diseases involves different cellular functions, including the well-established secretion of autoantibodies, autoantigen presentation and ensuing reciprocal interactions with T cells, secretion of inflammatory cytokines, and the generation of ectopic germinal centers. Through these mechanisms B cells are involved both in autoimmune diseases that are traditionally viewed as antibody mediated and also in autoimmune diseases that are commonly classified as T cell mediated. This new understanding of the role of B cells opened up novel therapeutic options for the treatment of autoimmune diseases. This paper includes an overview of the different functions of B cells in autoimmunity; the involvement of B cells in systemic lupus erythematosus, rheumatoid arthritis, and type 1 diabetes; and current B-cell-based therapeutic treatments. We conclude with a discussion of novel therapies aimed at the selective targeting of pathogenic B cells.

Lupus nephritis: role of antinucleosome autoantibodies

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

Amelioration of systemic lupus erythematosus by Withangulatin A in MRL/lpr mice

We have previously reported the anti-inflammatory potential and the possible underlying mechanisms of Withangulatin A (WA), which is an active component isolated from Physalis angulata L. Here, we demonstrated that WA might improve the life quality, as well as reduced the accumulation of proteinuria symptoms and levels of anti-double-stranded DNA antibodies in MRL/lpr mice. Moreover, WA could improve renal histopathologic characteristics of MRL/lpr mice. Intriguingly, expression of B cell-activating factor (BAFF), BAFF-R and related gene in the spleen were significantly reduced in 10 mg/kg WA-treated mice compared with that in 5 mg/kg WA-treated mice and untreated mice. These findings indicate that WA might have a pleiotropic therapeutic effect through their immunosuppression via inhibiting BAFF signaling, which suggest a potential application of this active constituent in the treatment of SLE.

Plasmacytoid dendritic cells and C1q differentially regulate inflammatory gene induction by lupus immune complexes

Immune complexes (ICs) play a pivotal role in causing inflammation in systemic lupus erythematosus (SLE). Yet, it remains unclear what the dominant blood cell type(s) and inflammation-related gene programs stimulated by lupus ICs are. To address these questions, we exposed normal human PBMCs or CD14(+) isolated monocytes to SLE ICs in the presence or absence of C1q and performed microarray analysis and other tests for cell activation. By microarray analysis, we identified genes and pathways regulated by SLE ICs that are both type I IFN dependent and independent. We also found that C1q-containing ICs markedly reduced expression of the majority of IFN-response genes and also influenced the expression of multiple other genes induced by SLE ICs. Surprisingly, IC activation of isolated CD14(+) monocytes did not upregulate CD40 and CD86 and only modestly stimulated inflammatory gene expression. However, when monocyte subsets were purified and analyzed separately, the low-abundance CD14(dim) ("patrolling") subpopulation was more responsive to ICs. These observations demonstrate the importance of plasmacytoid dendritic cells, CD14(dim) monocytes, and C1q as key regulators of inflammatory properties of ICs and identify many pathways through which they act.

Human matrix metalloproteinases: an ubiquitarian class of enzymes involved in several pathological processes

Human matrix metalloproteinases (MMPs) belong to the M10 family of the MA clan of endopeptidases. They are ubiquitarian enzymes, structurally characterized by an active site where a Zn(2+) atom, coordinated by three histidines, plays the catalytic role, assisted by a glutamic acid as a general base. Various MMPs display different domain composition, which is very important for macromolecular substrates recognition. Substrate specificity is very different among MMPs, being often associated to their cellular compartmentalization and/or cellular type where they are expressed. An extensive review of the different MMPs structural and functional features is integrated with their pathological role in several types of diseases, spanning from cancer to cardiovascular diseases and to neurodegeneration. It emerges a very complex and crucial role played by these enzymes in many physiological and pathological processes.

Immune-regulatory mechanisms in systemic autoimmune and rheumatic diseases

Systemic autoimmune and rheumatic diseases (SAIRDs) are thought to develop due to the failure of autoimmune regulation and tolerance. Current therapies, such as biologics, have improved the clinical results of SAIRDs; however, they are not curative treatments. Recently, new discoveries have been made in immune tolerance and inflammation, such as tolerogenic dendritic cells, regulatory T and B cells, Th 17 cells, inflammatory and tolerogenic cytokines, and intracellular signaling pathways. They lay the foundation for the next generation of the therapies beyond the currently used biologic therapies. New drugs should target the core processes involved in disease mechanisms with the aim to attain complete cure combined with safety and low costs compared to the biologic agents. Re-establishment of autoimmune regulation and tolerance in SAIRDs by the end of the current decade should be the final and realistic target.

Serum IgG levels demonstrate seasonal change in connective tissue diseases: a large-scale, 4-year analysis in Japanese

Hypergammaglobulinemia is often found in patients with autoimmune diseases, such as systemic lupus erythematosus (SLE), and its level may correlate with disease activity. However, it is unclear whether immunoglobulin G (IgG) displays seasonal changes. We analyzed the seasonal change in serum IgG by assessing 450 patients with connective tissue disease. The serum IgG levels in summer were compared with those in winter from 2006 to 2009. Independent samples from 355 patients were analyzed to confirm results in the first set. The differences in the IgG levels between the two seasons were analyzed in each disease and compared with disease activity. 488 patients without connective tissue disease were analyzed as reference instead of healthy people as control. We found that connective tissue disease patients tended to show higher levels of serum IgG in summer than in winter every year from 2006 to 2009, whereas patients without connective tissue disease did not demonstrate such a tendency. We observed this seasonal tendency in each disease. Seasonal changes weakly correlated with those of anti-DNA antibody in SLE patients and those of disease activity score in rheumatoid arthritis (RA) patients. Serum IgG levels of patients with connective tissue diseases display seasonal variations. Biological and clinical significance of these variations should be elucidated.

Alterations in circulating fatty acid composition in patients with systemic lupus erythematosus: a pilot study

INTRODUCTION

Circulating fatty acids (FAs) may play a role in the disease pathogenesis of patients with systemic lupus erythematosus (SLE).

OBJECTIVES

To compare red blood cell (RBC) and plasma FA composition: (1) between female SLE patients and age-matched healthy female (HF) controls and in SLE with history of cardiovascular disease (CVD) and those with no history (SLE+CVD vs SLE-CVD); and (2) between SLE patients who were or were not receiving prednisone treatment at the time of blood sampling.

METHODS

This cross-sectional study consisted of 33 female patients with SLE (11 SLE+CVD, 22 SLE-CVD) and 20 HF controls. Demographics, CVD risk, medication profile, blood biochemistry, and FA composition of RBC and plasma total lipids were determined.

RESULTS

Waist circumference and body mass index were higher in SLE patients than in HF controls. These variables along with serum triglycerides, blood glucose, and systolic blood pressure were higher in SLE+CVD than SLE-CVD patients. RBC FA composition showed lower eicosapentaenoic acid (EPA, ω-3 active metabolite) and ω-3 index (EPA+ docosahexaenoic acid) in SLE patients compared with HF controls. The ratio of the RBC inflammatory metabolite, arachidonic acid, to the anti-inflammatory metabolite EPA was also significantly higher in SLE patients than in HF controls. No differences were seen in plasma FA between SLE and HF groups. However, SLE-CVD patients had a more favorable lipid profile than SLE+CVD patients. In SLE patients, the use of prednisone resulted in alteration of both RBC and plasma FA composition.

CONCLUSION

SLE patients, regardless of their history of CVD, have altered plasma and RBC FA composition favoring inflammation. The use of prednisone was associated with differences in FA profile.

Lupus nephritis: current update

Lupus nephritis is a major cause of morbidity and mortality in patients with systemic lupus erythematosus. The general consensus is that 60% of lupus patients will develop clinically relevant nephritis at some time in the course of their illness. Prompt recognition and treatment of renal disease is important, as early response to therapy is correlated with better outcome. The present review summarizes our current understanding of the pathogenic mechanisms underlying lupus nephritis and how the disease is currently diagnosed and treated.

Phenotyping of P105-negative B cell subsets in patients with systemic lupus erythematosus

This study aimed to investigate phenotype of RP105(-) B cell subsets in patients with systemic lupus erythematosus (SLE). Flow cytometry was used for phenotyping RP105-negaive B cell subsets. Based on CD19, RP105, and CD138 expression, RP105(-) B cells consist of at least 5 subsets of late B cells, including CD19(+)RP105(int), CD19(+) RP105(-), CD19(low) RP105(-) CD138(-), CD19(low) RP105(-)CD138(int), and CD19(low) RP105(-) CD138(++) B cells. Especially, CD19(+)RP105(int) and CD19(low) RP105(-)CD138(int) B cells are significantly larger than other RP105(-) B cell subsets in SLE. By comparison of RP105(-) B cell subsets between patients with SLE and normal subjects, these subsets were detectable even in normal subjects, but the percentages of RP105(-) B cell subsets were significantly larger in SLE. The phenotypic analysis of RP105(-) B cell subsets suggests dysregulation of later B cell subsets in SLE and may provide new insights into understanding regulation of B cells in human SLE.

RP105-negative B cells in systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a multisystem disease characterized by B cells producing autoantibodies against nuclear proteins and DNA, especially anti-double-strand DNA (dsDNA) antibodies. RP105 (CD180), the toll-like receptor- (TLR-) associated molecule, is expressed on normal B cells. However, RP105-negative B cells increase in peripheral blood from patients with active SLE. RP105 may regulate B-cell activation, and RP105-negative B cells produce autoantibodies and take part in pathophysiology of SLE. It is possible that targeting RP105-negative B cells is one of the treatments of SLE. In this paper, we discuss the RP105 biology and clinical significance in SLE.

Microparticles as a source of extracellular DNA

Microparticles are small membrane-bound vesicles that display pro-inflammatory and pro-thrombotic activities important in the pathogenesis of a wide variety of diseases. These particles are released from activated and dying cells and incorporate nuclear and cytoplasmic molecules for extracellular export. Of these molecules, DNA is a central autoantigen in systemic lupus erythematosus (SLE). As studies in our laboratory show, DNA occurs prominently in microparticles, translocating into these structures during apoptotic cell death. This DNA is antigenically active and can bind to lupus anti-DNA autoantibodies. These findings suggest that microparticles are an important source of extracellular DNA to serve as an autoantigen and autoadjuvant in SLE.

Subset size, activation threshold and distribution of autoreactive MZ and FO B cells do not differ in a sex-specific manner in the NZB/W F1 murine lupus model: an experimental mouse study

OBJECTIVES

Systemic lupus erythematosus (SLE) shows a strong sex bias, preferentially affecting females, and B cells are thought to play a pivotal role in its pathogenesis. Here, we compared the splenic B-cell compartments, their autoreactivity and activation threshold of female and male NZB/W F1, a murine lupus model reflecting the sex bias observed in patients with SLE.

METHODS

Autoantibody levels and the amount of autoantibody secreting cells were determined using ELISA and ELISPOT. Flow cytometry and immunofluorescence were applied to analyse the composition of the splenic B-cell pool. Purified follicular (FO) and marginal zone (MZ) B cells were stimulated and the frequency of autoreactive cells was determined. Finally, the proliferative response of FO and MZ B cells upon stimulation was assessed using CFSE dilution and [(3)H]-Thymidin incorporation.

RESULTS

Higher autoantibody titres were detected in female NZB/W F1 mice, which were mainly produced in the spleen. Analysing the composition of the splenic B-cell subsets, no differences were found prior to disease development. Autoreactive dsDNA-specific B cells were mostly found in the MZ compartment, while SmD1((83-119))-reactive cells were more evenly distributed. Equal frequencies of autoreactive B cells were found in female and malemice, and no difference in the response to polyclonal stimuli of the cells of both sexes was detected.

CONCLUSIONS

No differences in the composition or functionality of splenic B cells were observed that account for the different disease course in both sexes.

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSION

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

Are autoantibodies the targets of B-cell-directed therapy?

B-cell-directed therapy-the use of agents that eliminate B cells or block cytokines important for B-cell function-is emerging as a promising approach to the treatment of rheumatic disease. Target diseases, including systemic lupus erythematosus (SLE), display diverse patterns of autoantibody production and aberrant activation of B cells. Despite the success of this general approach, the mechanisms by which B-cell-directed therapy ameliorates disease, and the role of autoantibodies as biomarkers of clinical response remain unclear. Importantly, although B-cell-directed therapy can reduce the production of some autoantibodies, the effects can be variable and heterogeneous, probably reflecting the critical (but ill-defined) roles of different B-cell and plasma cell populations in autoantibody production. Future studies during clinical trials of these agents are needed to define which B-cell and autoantibody populations are affected (or ought to be), and to discover informative biomarkers of clinical response that can be used to advance this therapeutic approach.

Macrophage differentiation and polarization via phosphatidylinositol 3-kinase/Akt-ERK signaling pathway conferred by serum amyloid P component

Macrophage differentiation and polarization is influenced by, and act on, many processes associated with autoimmunity. However, the molecular mechanisms underlying macrophage polarization in systemic lupus erythematosus (SLE) remain largely debated. We previously demonstrated that macrophage M2b polarization conferred by activated lymphocyte-derived (ALD)-DNA immunization could initiate and propagate murine lupus nephritis. Serum amyloid P component (SAP), a conserved acute-phase protein in mice, has been reported to bind to DNA and modulate immune responses. In this study, murine SAP was shown to promote macrophage-mediated ALD-DNA uptake through binding to ALD-DNA (SAP/ALD-DNA). Moreover, macrophage phenotypic switch from a proinflammatory M2b phenotype induced by ALD-DNA alone to an anti-inflammatory M2a phenotype stimulated with SAP/ALD-DNA were found because of PI3K/Akt-ERK signaling activation. Both in vivo SAP supplements and adoptive transfer of ex vivo programmed M2a macrophages induced by SAP/ALD-DNA into SLE mice could efficiently alleviate lupus nephritis. Importantly, increased IL-10 secretion, accompanied by anti-inflammatory effect exerted by M2a macrophages, was found to predominantly impede macrophage M2b polarization. Furthermore, neutralization of IL-10 notably reduced the suppressive effect of M2a macrophages. Our results demonstrate that binding of SAP to ALD-DNA could switch macrophage phenotypic polarization from proinflammatory M2b to anti-inflammatory M2a via PI3K/Akt-ERK signaling activation, thus exerting protective and therapeutic interventions on murine lupus nephritis. These data provide a possible molecular mechanism responsible for modulation of macrophage polarization in the context of lupus nephritis and open a new potential therapeutic avenue for SLE.

High frequency of autoantibody-secreting cells and long-lived plasma cells within inflamed kidneys of NZB/W F1 lupus mice

Autoantibodies to double-stranded (ds) DNA represent a serological hallmark of systemic lupus erythematosus (SLE) and may critically contribute to the pathogenesis of lupus nephritis. Self-reactive antibodies might be partially produced by long-lived plasma cells (PCs), which mainly reside within the bone marrow and spleen. In contrast to short-lived PCs, long-lived PCs are extremely resistant to therapy and may sustain refractory disease courses. Recently, antibody-secreting cells were found within the inflamed kidneys of New Zealand black/white (NZB/W) F1 lupus mice as well as of patients with SLE. To analyze the longevity of the IgG-producing cells present in nephritic kidneys of NZB/W F1 mice we performed in vivo BrdU-labeling. We identified a higher frequency of long-lived than short-lived renal PCs, indicating that survival niches for long-lived PCs also exist within inflamed kidneys. Using ELISPOT assays, we found that on average 31% of renal IgG-producing cells reacted with dsDNA and 24% with nucleolin. Moreover, the frequencies of IgG-secreting cells specific for the autoantigens dsDNA and nucleolin were higher in the kidneys compared with those in the spleen and bone marrow.

Chromatin as a target antigen in human and murine lupus nephritis

The present review focuses on pathogenic molecular and transcriptional events in patients with lupus nephritis. These factors are renal DNaseI, exposed chromatin fragments and the corresponding chromatin-reactive autoantibodies. Lupus nephritis is the most serious complication in human systemic lupus erythematosus, and is characterised by deposition of chromatin fragment-IgG complexes in the mesangial matrix and glomerular basement membranes. The latter deposition defines end-stage disease. This event is stringently linked to a renal-restricted shutdown of expression of the DNaseI gene, as determined by loss of DNaseI mRNA level and DNaseI enzyme activity. The major aim of the present review is to generate new therapeutic strategies based on new insight into the disease pathogenesis.

Abrogation of pathogenic IgG autoantibody production in CD40L gene-deleted lupus-prone New Zealand Black mice

New Zealand Black (NZB) mice spontaneously develop a lupus-like autoimmune disease. Since CD40-CD40L interactions are important for B cell class-switch recombination and germinal center formation, we sought to understand the impact of these interactions on the immune abnormalities in NZB CD40L gene-deleted (CD40L(-/-)) mice in vivo. NZB.CD40L(-/-) mice demonstrated abrogation of all IgG autoantibodies tested and attenuated kidney disease. However, polyclonal B cell activation in vivo and B cell proliferation and class-switching in response to TLR ligands in vitro were preserved in the absence of CD40L in NZB mice. Although, plasmacytoid dendritic cell expansion and elevated BAFF production were unaffected by the absence of CD40L, there was some evidence that IFN-α-induced gene expression was reduced in the bone marrow of NZB.CD40L(-/-) mice. Our results suggest that CD40-CD40L interactions play an important role in promoting pathogenic IgG autoantibody production and kidney disease in NZB mice.

Thrombotic microangiopathic hemolytic anemia with reduction of ADAMTS13 activity: initial manifestation of childhood-onset systemic lupus erythematosus

Severe manifestations of systemic lupus erythematosus (SLE), antiphospholipid syndrome (APS), and thrombotic thrombocytopenic purpura (TTP) are characterized by multiorgan thrombotic microangiopathy. We describe reduction of ADAMTS13 activity and the development of systemic autoimmunity in all 8 children initially diagnosed with acquired noncongenital TTP during an 8.5-year period. Median age at diagnosis was 12.0 years (range, 2.6-17.3 years). ADAMTS13 activity was absent (<5%) in 6 patients; 3 patients had a detected inhibitor. SLE was diagnosed concurrently in 3 patients, and 4 patients were diagnosed within 5 years. Six of the children diagnosed with SLE had absent ADAMTS13 activity at diagnosis. In 6 patients with SLE, immune-mediated nephritis developed by 46 months. All surviving patients with SLE developed antiphospholipid antibodies, including some with a lupus anticoagulant. Patients with SLE did not have TTP recurrences once daily immunosuppressive regimens were started. An evaluation for SLE/APS is warranted in children and adolescents with reduced ADAMTS13 activity and thrombotic microangiopathy.

Interferon-α induces unabated production of short-lived plasma cells in pre-autoimmune lupus-prone (NZB×NZW)F1 mice but not in BALB/c mice

IFN-α is known to play a critical role in the pathogenesis of systemic lupus erythematosus (SLE), but the mechanisms remain unclear. We previously showed that within weeks, exposure to IFN-α in vivo induces lupus in pre-autoimmune lupus-prone NZB×NZW F1 (NZB/W) but not in BALB/c mice. In the current study, we show that in vivo expression of IFN-α induces sustained B-cell proliferation in both BALB/c and NZB/W mice. In NZB/W but not BALB/c mice, B-cell proliferation was accompanied by a rapid and unabated production of autoantibody-secreting cells (ASCs) in secondary lymphoid organs, suggesting that a B-cell checkpoint is altered in the autoimmune background. The majority (>95%) of ASCs elicited in IFN-α-treated NZB/W mice were short-lived and occurred without the induction of long-lived plasma cells. A short course of cyclophosphamide caused a sharp drop in IFN-α-elicited short-lived plasma cells, but the levels recovered within days following termination of treatment. Thus, our work provides new insights into effectiveness and limitations of the current SLE therapies.

Anti-dsDNA-NcX ELISA: dsDNA-loaded nucleosomes improve diagnosis and monitoring of disease activity in systemic lupus erythematosus

INTRODUCTION

The objective of this study was to compare the clinical usefulness of the new anti-double-stranded DNA nucleosome-complexed enzyme-linked immunosorbent assay (Anti-dsDNA-NcX ELISA), which is based on dsDNA-loaded nucleosomes as antigens, with established test systems based on dsDNA or nucleosomes alone for systemic lupus erythematosus (SLE) diagnostics and determination of disease activity.

METHODS

Sera from a cohort of 964 individuals comprising 207 SLE patients, 357 disease controls and 400 healthy donors were investigated using the Anti-dsDNA-NcX ELISA, Farr assay, Anti-dsDNA ELISA, Anti-nucleosome ELISA and Crithidia luciliae immunofluorescence (CLIF) assay, all of which are tests available from EUROIMMUN Medizinische Labordiagnostika AG (Lübeck, Germany). Receiver operating characteristic curve analyses were performed to compare the sensitivity and specificity of each assay. The test results yielded by these assays in a group of 165 fully characterized SLE patients were compared with the corresponding medical records.

RESULTS

The Anti-dsDNA-NcX ELISA was found to have a sensitivity of 60.9% and a specificity of 98.9% in all 964 individuals at the manufacturer's cutoff of 100 U/ml. At a comparable specificity of 99%, the sensitivity amounted to 59.9% for the Anti-dsDNA-NcX ELISA, 54.1% for the Farr assay, 53.6% for the antinucleosome ELISA and 35.8% for the anti-dsDNA ELISA. The CLIF assay had a sensitivity of 28.0% and a specificity of 98.2%. The Anti-dsDNA-NcX ELISA correlated mostly with global disease activity in a cross-sectional analysis. In a longitudinal analysis of 20 patients with 69 patient visits, changes in Anti-dsDNA-NcX ELISA and antinucleosome ELISA results correlated highly with changes in disease activity over time.

CONCLUSIONS

The use of dsDNA-complexed nucleosomes as antigens in ELISA leads to optimized determination of diagnosis and disease activity in SLE patients and is available for clinical practice.

Alpha-actinin: a multidisciplinary protein with important role in B-cell driven autoimmunity

Alpha-actinin (α-actinin) is a ubiquitous cytoskeletal protein, which belongs to the superfamily of filamentous actin (F-actin) crosslinking proteins. It is present in multiple subcellular regions of both muscle and non-muscle cells, including cell-cell and cell-matrix contact sites, cellular protrusions and stress fiber dense regions and thus, it seems to bear multiple important roles in the cell by linking the cytoskeleton to many different transmembrane proteins in a variety of junctions. Four isoforms of human α-actinin have already been identified namely, the "muscles" α-actinin-2 and α-actinin-3 and the "non-muscles" α-actinin-1 and α-actinin-4. The precise functions of α-actinin isoforms as well as the precise role and significance of their binding to F-actin particularly in-vivo, have been elusive. They are generally believed to represent key structural components of large-scale F-actin cohesion in cells required for cell shape and motility. α-Actinin-2 has been implicated in myopathies such as nemalin body myopathy, hypertrophic and dilated cardiomyopathy and it may have at least an indirect pathogenetic role in diseases of the central nervous system (CNS) like schizophrenia, epilepsy, ischemic brain damage, CNS lupus and neurodegenerative disorders. The role of "non-muscle" α-actinins in the kidney seems to be crucial as an essential component of the glomerular filtration barrier. Therefore, they have been implicated in the pathogenesis of familial focal segmental glomerulosclerosis, nephrotic syndrome, IgA nephropathy, focal segmental glomerulosclerosis and minimal change disease. α-Actinin is also expressed on the membrane and cytosol of parenchymal and ductal cells of the liver and it seems that it interacts with hepatitis C virus in an essential way for the replication of the virus. Finally α-actinin, especially α-actinin-4, has been implicated in cancer cell progression and metastasis, as well as the migration of several cell types participating in the immune response. Based on these functions, the accumulating reported evidence of the importance of α-actinin as a target autoantigen in the pathogenesis of autoimmune diseases, particularly systemic lupus erythematosus and autoimmune hepatitis, is also discussed along with the possible perspectives that are potentially emerging from the study of this peculiar molecule in health and disease.

Inefficient clearance of dying cells in patients with SLE: anti-dsDNA autoantibodies, MFG-E8, HMGB-1 and other players

Systemic lupus erythematosus (SLE) is a complex disease resulting from inflammatory responses of the immune system against several autoantigens. Inflammation is conditioned by the continuous presence of autoantibodies and leaked autoantigens, e.g. from not properly cleared dying and dead cells. Various soluble molecules and biophysical properties of the surface of apoptotic cells play significant roles in the appropriate recognition and further processing of dying and dead cells. We exemplarily discuss how Milk fat globule epidermal growth factor 8 (MFG-E8), biophysical membrane alterations, High mobility group box 1 (HMGB1), C-reactive protein (CRP), and anti-nuclear autoantibodies may contribute to the etiopathogenesis of the disease. Up to date knowledge about these key elements may provide new insights that lead to the development of new treatment strategies of the disease.

Gene expression profiles in a rabbit model of systemic lupus erythematosus autoantibody production

We previously reported the establishment of a rabbit (Oryctolagus cuniculus) model in which peptide immunization led to production of lupus-like autoantibodies including anti-Sm, -RNP, -SS-A, -SS-B, and -dsDNA characteristic of those produced in systemic lupus erythematosus (SLE) patients. Some neurologic symptoms in the form of seizures and nystagmus were observed. The animals used in the previous and in the current study were from a National Institute of Allergy and Infectious Diseases colony of rabbits that were pedigreed, Ig-allotype defined, but not inbred. Their genetic heterogeneity may correspond to that found among patients of a given ethnicity. We extended the information about this rabbit model by microarray-based expression profiling. We first demonstrated that human expression arrays could be used with rabbit RNA to yield information on molecular pathways. We then designed a study evaluating gene expression profiles in eight groups of control and treated rabbits (47 rabbits in total). Genes significantly upregulated in treated rabbits were associated with NK cytotoxicity, Ag presentation, leukocyte migration, cytokine activity, protein kinases, RNA spliceosomal ribonucleoproteins, intracellular signaling cascades, and glutamate receptor activity. These results link increased immune activation with upregulation of components associated with neurologic and anti-RNP responses, demonstrating the utility of the rabbit model to uncover biological pathways related to SLE-induced clinical symptoms, including neuropsychiatric lupus. Our finding of distinct gene expression patterns in rabbits that made anti-dsDNA compared with those that only made other anti-nuclear Abs should be further investigated in subsets of SLE patients with different autoantibody profiles.

Preclinical rheumatoid arthritis: identification, evaluation, and future directions for investigation

Rheumatoid arthritis (RA) likely develops in several phases, beginning with genetic risk, followed by asymptomatic autoimmunity, then finally, clinically apparent disease. Investigating the phases of disease that exist prior to the onset of symptoms (ie, the preclinical period of RA) will lead to understanding of the important relationships between genetic and environmental factors that may lead to disease, as well as allow for the development of predictive models for disease, and ultimately preventive strategies for RA.

A role for the B-cell CD74/macrophage migration inhibitory factor pathway in the immunomodulation of systemic lupus erythematosus by a therapeutic tolerogenic peptide

Systemic lupus erythematosus (SLE) is an autoimmune disease that involves dysregulation of B and T cells. A tolerogenic peptide, designated hCDR1, ameliorates disease manifestations in SLE-afflicted mice. In the present study, the effect of treatment with hCDR1 on the CD74/macrophage migration inhibitory factor (MIF) pathway was studied. We report here that B lymphocytes from SLE-afflicted mice express relatively elevated levels of CD74, compared with B cells from healthy mice. CD74 is a receptor found in complex with CD44, and it binds the pro-inflammatory cytokine MIF. The latter components were also up-regulated in B cells from the diseased mice, and treatment with hCDR1 resulted in their down-regulation and in reduced B-cell survival. Furthermore, up-regulation of CD74 and CD44 expression was detected in brain hippocampi and kidneys, two target organs in SLE. Treatment with hCDR1 diminished the expression of those molecules to the levels determined for young healthy mice. These results suggest that the CD74/MIF pathway plays an important role in lupus pathology.

Renal Dnase1 enzyme activity and protein expression is selectively shut down in murine and human membranoproliferative lupus nephritis

Background

Deposition of chromatin-IgG complexes within glomerular membranes is a key event in the pathogenesis of lupus nephritis. We recently reported an acquired loss of renal Dnase1 expression linked to transformation from mild to severe membranoproliferative lupus nephritis in (NZBxNZW)F1 mice. As this may represent a basic mechanism in the progression of lupus nephritis, several aspects of Dnase1 expression in lupus nephritis were analyzed.

Methodology/Principal Findings

Total nuclease activity and Dnase1 expression and activity was evaluated using in situ and in vitro analyses of kidneys and sera from (NZBxNZW)F1 mice of different ages, and from age-matched healthy controls. Immunofluorescence staining for Dnase1 was performed on kidney biopsies from (NZBxNZW)F1 mice as well as from human SLE patients and controls. Reduced serum Dnase1 activity was observed in both mesangial and end-stage lupus nephritis. A selective reduction in renal Dnase1 activity was seen in mice with massive deposition of chromatin-containing immune complexes in glomerular capillary walls. Mice with mild mesangial nephritis showed normal renal Dnase1 activity. Similar differences were seen when comparing human kidneys with severe and mild lupus nephritis. Dnase1 was diffusely expressed within the kidney in normal and mildly affected kidneys, whereas upon progression towards end-stage renal disease, Dnase1 was down-regulated in all renal compartments. This demonstrates that the changes associated with development of severe nephritis in the murine model are also relevant to human lupus nephritis.

Conclusions/Significance

Reduction in renal Dnase1 expression and activity is limited to mice and SLE patients with signs of membranoproliferative nephritis, and may be a critical event in the development of severe forms of lupus nephritis. Reduced Dnase1 activity reflects loss in the expression of the protein and not inhibition of enzyme activity.

Decreased incidence of lupus nephritis in northern Norway is linked to increased use of antihypertensive and anticoagulant therapy

BACKGROUND

Lupus nephritis (LN) remains a severe complication in systemic lupus erythematosus (SLE). Over the last decade, antiphospholipid antibodies have become a part of SLE classification criteria, and awareness of cardiovascular morbidity and its risk factors in SLE has increased. This study investigated the potential effect of these alterations on the presentation and severity of LN.

METHODS

This is an observational study of two subsequent SLE inception cohorts based on 1982 American College of Rheumatology (acr) classification criteria (82acr; n=87, enrolled 1978-95) and the updated version in 1997 (97acr: n=62, enrolled 1996-2006). Annual incidence rates (AIR), point prevalence, clinical and histological features, and outcome of LN (defined as proteinuria with urinary casts and/or haematuria) were compared between both cohorts.

RESULTS

Between 1978 and 2006, the AIR for LN decreased from 0.7 to 0.45/100 000, while LN prevalence rose from 7 to 14/100 000. The relative risk reduction in the 97acr for early- and late-onset LN (> 3 months after SLE diagnosis) was 39% and 42%, respectively. Patients developing LN in the 97acr cohort (97LN+; n=11) had similar demographics, more often low avidity anti-dsDNA antibodies (Ab) and/or anti-cardiolipin Ab at SLE diagnosis, lower proteinuria and diastolic blood pressure, and similar histological findings to those in the 83acr cohort (82LN +; n=28). Following LN diagnosis, more 97LN + patients received pulse corticosteroids (55% vs. 7%), anticoagulants (46% vs. 4%) and antihypertensive drugs (46% vs. 11%). Three 82LN+ patients (11%) developed end-stage renal disease versus none in 97LN + during a 10-year follow-up.

CONCLUSIONS

Early detection of low avidity anti-dsDNA and antiphospholipid antibodies, probably in combination with early use of protective cardiovascular measures from SLE diagnosis onwards may contribute to reduced incidence and improved renal survival in LN.

TLR recognition of self nucleic acids hampers glucocorticoid activity in lupus

Glucocorticoids are widely used to treat patients with autoimmune diseases such as systemic lupus erythematosus (SLE). However, regimens used to treat many such conditions cannot maintain disease control in the majority of SLE patients and more aggressive approaches such as high-dose methylprednisolone pulse therapy are used to provide transient reductions in disease activity. The primary anti-inflammatory mechanism of glucocorticoids is thought to be NF-kappaB inhibition. Recognition of self nucleic acids by toll-like receptors TLR7 and TLR9 on B cells and plasmacytoid dendritic cells (PDCs) is an important step in the pathogenesis of SLE, promoting anti-nuclear antibodies and the production of type I interferon (IFN), both correlated with the severity of disease. Following their activation by self-nucleic acid-associated immune complexes, PDCs migrate to the tissues. We demonstrate, in vitro and in vivo, that stimulation of PDCs through TLR7 and 9 can account for the reduced activity of glucocorticoids to inhibit the IFN pathway in SLE patients and in two lupus-prone mouse strains. The triggering of PDCs through TLR7 and 9 by nucleic acid-containing immune complexes or by synthetic ligands activates the NF-kappaB pathway essential for PDC survival. Glucocorticoids do not affect NF-kappaB activation in PDCs, preventing glucocorticoid induction of PDC death and the consequent reduction of systemic IFN-alpha levels. These findings unveil a new role for self nucleic acid recognition by TLRs and indicate that inhibitors of TLR7 and 9 signalling could prove to be effective corticosteroid-sparing drugs.