Cellular and molecular pathogenesis of systemic lupus erythematosus: lessons from animal models

A Novel Human Interleukin-23A Overexpressing Mouse Model of Systemic Lupus Erythematosus

OBJECTIVE

Interleukin-23 (IL-23) is a crucial cytokine implicated in chronic inflammation and autoimmunity, associated with various diseases such as psoriasis, psoriatic arthritis, and systemic lupus erythematosus (SLE). This study aimed to create and characterize a transgenic mouse model overexpressing human IL-23A (TghIL-23A), providing a valuable tool for investigating the pathogenic role of human IL-23A and evaluating the efficacy of anti-human IL-23A therapeutics.

METHODS

TghIL-23A mice were generated via microinjection of CBA × C57BL/6 zygotes with a fragment of the human IL23A gene, flanked by its 5'-regulatory sequences and the 3' untranslated region of human β-globin. The TghIL-23A pathology was assessed through hematologic and biochemic analyses, cytokine and antinuclear antibody detection, and histopathologic examination of skin and renal tissues. The response to the anti-human IL-23A therapeutic agent guselkumab was evaluated in groups of eight mixed-sex mice receiving subcutaneous treatment twice weekly for 10 weeks using clinical, biomarker, and histopathologic readouts.

RESULTS

TghIL-23A mice exhibited interactions between human IL-23A and mouse IL-23/IL-12p40 and developed a chronic multiorgan autoimmune disease marked by proteinuria, anti-double-stranded DNA antibodies, severe inflammatory lesions in the skin, and milder phenotypes in the kidneys and lungs. The TghIL-23A pathologic features exhibited significant similarities to those observed in human patients with SLE, and they were reversed following guselkumab treatment.

CONCLUSION

We have generated and characterized a novel genetic mouse model of SLE, providing proof-of-concept for the etiopathogenic role of human IL-23A. This new model has a normal life span and integrates several characteristics of the human disease's complexity and chronicity, making it an attractive preclinical tool for studying IL-23-dependent pathogenic mechanisms and assessing the efficacy of anti-human IL-23A or modeled disease-related therapeutics.

Autoimmune Responses and Therapeutic Interventions for Systemic Lupus Erythematosus: A Comprehensive Review

Systemic Lupus Erythematosus (SLE) or Lupus is a multifactorial autoimmune disease of multiorgan malfunctioning of extremely heterogeneous and unclear etiology that affects multiple organs and physiological systems. Some racial groups and women of childbearing age are more susceptible to SLE pathogenesis. Impressive progress has been made towards a better understanding of different immune components contributing to SLE pathogenesis. Recent investigations have uncovered the detailed mechanisms of inflammatory responses and organ damage. Various environmental factors, pathogens, and toxicants, including ultraviolet light, drugs, viral pathogens, gut microbiome metabolites, and sex hormones trigger the onset of SLE pathogenesis in genetically susceptible individuals and result in the disruption of immune homeostasis of cytokines, macrophages, T cells, and B cells. Diagnosis and clinical investigations of SLE remain challenging due to its clinical heterogeneity and hitherto only a few approved antimalarials, glucocorticoids, immunosuppressants, and some nonsteroidal anti-inflammatory drugs (NSAIDs) are available for treatment. However, the adverse effects of renal and neuropsychiatric lupus and late diagnosis make therapy challenging. Additionally, SLE is also linked to an increased risk of cardiovascular diseases due to inflammatory responses and the risk of infection from immunosuppressive treatment. Due to the diversity of symptoms and treatment-resistant diseases, SLE management remains a challenging issue. Nevertheless, the use of next-generation therapeutics with stem cell and gene therapy may bring better outcomes to SLE treatment in the future. This review highlights the autoimmune responses as well as potential therapeutic interventions for SLE particularly focusing on the recent therapeutic advancements and challenges.

SOCS-JAK-STAT inhibitors and SOCS mimetics as treatment options for autoimmune uveitis, psoriasis, lupus, and autoimmune encephalitis

Autoimmune diseases arise from atypical immune responses that attack self-tissue epitopes, and their development is intricately connected to the disruption of the JAK-STAT signaling pathway, where SOCS proteins play crucial roles. Conditions such as autoimmune uveitis, psoriasis, lupus, and autoimmune encephalitis exhibit immune system dysfunctions associated with JAK-STAT signaling dysregulation. Emerging therapeutic strategies utilize JAK-STAT inhibitors and SOCS mimetics to modulate immune responses and alleviate autoimmune manifestations. Although more research and clinical studies are required to assess their effectiveness, safety profiles, and potential for personalized therapeutic approaches in autoimmune conditions, JAK-STAT inhibitors and SOCS mimetics show promise as potential treatment options. This review explores the action, effectiveness, safety profiles, and future prospects of JAK inhibitors and SOCS mimetics as therapeutic agents for psoriasis, autoimmune uveitis, systemic lupus erythematosus, and autoimmune encephalitis. The findings underscore the importance of investigating these targeted therapies to advance treatment options for individuals suffering from autoimmune diseases.

HPV and molecular mimicry in systemic lupus erythematosus and an impact of compiling B-cell epitopes and MHC-class II binding profiles with in silico evidence

Epidemiological link between HPV and SLE is evolving. The possibility of HPV infection-induced molecular mimicry and systemic lupus erythematosus (SLE) was elucidated through detailed in silico analyses. Conserved regions in the structural protein sequences of high-risk HPV types were inferred, and sequence homologies between viral and human peptides were identified to delineate proteins implicated in SLE. B-cell epitopes and MHC-class II binding were compiled using Immune Epitope Database and ProPred II analysis tool. Molecular modeling and molecular dynamics/simulation (MDS) were performed using AutoDock Vina and GROMACS, respectively. Sequence alignment revealed 32 conserved regions, and 27/32 viral peptides showed varying similarities to human peptides, rich in B-cell epitopes with superior accessibility, high hydrophilicity, antigenicity and disposition to bind many class-II HLA alleles. Molecular docking of 13 viral peptides homologous (100%) to human peptides implicated in SLE showed that VIR-PEP1 (QLFNKPYWL) and VIR-PEP2 (DTYRFVTS) exhibited higher binding affinities than corresponding human peptides to SLE predisposing HLA-DRB1 allele. MDS of these peptides showed that the viral peptides had superior folding, compactness, and a higher number of hydrogen bonds than human peptides throughout the simulation period. SASA analysis revealed that the VIR-PEP1&2 fluctuated less frequently than corresponding human peptides. MM-PBSA revealed that the VIR-PEP2 complex exhibited higher binding energy than the human peptide complex. This suggests that highly conserved structural peptides of high-risk HPV types homologous to human peptides could compete and bind avidly to the HLA allele associated with SLE and predispose HPV-infected individuals to SLE through molecular mimicry.Communicated by Ramaswamy H. Sarma.

The emerging role of noncoding RNAs in systemic lupus erythematosus: new insights into the master regulators of disease pathogenesis

Auto-immune diseases are a form of chronic disorders in which the immune system destroys the body's cells due to a loss of tolerance to self-antigens. Systemic lupus erythematosus (SLE), identified by the production of autoantibodies in different body parts, is one of the most well-known examples of these diseases. Although the etiology of SLE is unclear, the disease's progression may be affected by genetic and environmental factors. As studies in twins provide adequate evidence for genetic involvement in the SLE, other phenomena such as metallization, histone modifications, and alterations in the expression of noncoding RNAs (ncRNAs) also indicate the involvement of epigenetic factors in this disease. Among all the epigenetic alterations, ncRNAs appear to have the most crucial contribution to the pathogenesis of SLE. The ncRNAs' length and size are divided into three main classes: micro RNAs, long noncoding RNAs (LncRNA), and circular RNAs (circRNAs). Accumulating evidence suggests that dysregulations in these ncRNAs contributed to the pathogenesis of SLE. Hence, clarifying the function of these groups of ncRNAs in the pathophysiology of SLE provides a deeper understanding of the disease. It also opens up new opportunities to develop targeted therapies for this disease.

Omega-3 fatty acids: Current insights into mechanisms of action in systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is one of the autoimmune diseases characterized by the lack of self-tolerance and the formation of immune complexes and nuclear autoantigens resulting in inflammation in multiple organs. Nowadays, the major aim of SLE therapy is the control of disease activity. However, the biological heterogeneity between patients and the absence of safe and specific targeted treatments complicate the lupus management. Therefore, the potential prophylactic effects of natural therapy considering the potential side effects of classical pharmacology, also the role of diet therapy in decreasing co-morbidities and improving quality of life in SLE patients could be a promising approach to SLE disease. Omega-3 polyunsaturated fatty acids (omega-3 PUFAs) are one of the agents that are considered for their preventive and therapeutic properties in disease activity of SLE and the related complications. The intake of omega-3 PUFAs likely has a direct relationship with improvements in inflammatory, cardiovascular, depressive, and neuromotor symptoms of the patients. The current review summarizes clinical and preclinical studies with comprehensive insights into the mechanisms of action of omega-3 fatty acids (omega-3 FAs) in Systemic Lupus Erythematosus to provide an update on the negative and positive aspects of the intake of omega-3 FAs in SLE patients.

Lipid Metabolism: Immune Regulation and Therapeutic Prospectives in Systemic Lupus Erythematosus

Systemic lupus erythematosus (SLE) is a heterogeneous disease characterized by the production of abnormal autoantibodies and immune complexes that can affect the organ and organ systems, particularly the kidneys and the cardiovascular system. Emerging evidence suggests that dysregulated lipid metabolism, especially in key effector cells, such as T cells, B cells, and innate immune cells, exerts complex effects on the pathogenesis and progression of SLE. Beyond their important roles as membrane components and energy storage, different lipids can also modulate different cellular processes, such as proliferation, differentiation, and survival. In this review, we summarize altered lipid metabolism and the associated mechanisms involved in the pathogenesis and progression of SLE. Furthermore, we discuss the recent progress in the role of lipid metabolism as a potential therapeutic target in SLE.

The JAK/STAT signaling pathway: from bench to clinic

The Janus kinase/signal transducer and activator of transcription (JAK/STAT) signaling pathway was discovered more than a quarter-century ago. As a fulcrum of many vital cellular processes, the JAK/STAT pathway constitutes a rapid membrane-to-nucleus signaling module and induces the expression of various critical mediators of cancer and inflammation. Growing evidence suggests that dysregulation of the JAK/STAT pathway is associated with various cancers and autoimmune diseases. In this review, we discuss the current knowledge about the composition, activation, and regulation of the JAK/STAT pathway. Moreover, we highlight the role of the JAK/STAT pathway and its inhibitors in various diseases.

The JAK/STAT signaling pathway: from bench to clinic

The Janus kinase/signal transducer and activator of transcription (JAK/STAT) signaling pathway was discovered more than a quarter-century ago. As a fulcrum of many vital cellular processes, the JAK/STAT pathway constitutes a rapid membrane-to-nucleus signaling module and induces the expression of various critical mediators of cancer and inflammation. Growing evidence suggests that dysregulation of the JAK/STAT pathway is associated with various cancers and autoimmune diseases. In this review, we discuss the current knowledge about the composition, activation, and regulation of the JAK/STAT pathway. Moreover, we highlight the role of the JAK/STAT pathway and its inhibitors in various diseases.

Assessing Lupus-Like Disease in Murine Model Systems

Systemic Lupus Erythematosus (SLE) is a complex and heterogenous autoimmune disease, where genetics, immunology, and environmental factors all play a role. Murine models have contributed critical information on mechanisms of disease and prospective therapeutics. The key features that have been used to study the disease include the development of anti-nuclear autoantibodies (ANAs), splenomegaly, and kidney disease. The loss of tolerance and subsequent autoimmune features, and the progression to severe disease, are all dependent on immune dysregulation. In this article, we will describe the methods used to evaluate the underlying immunological features of the disease, as a more sensitive strategy to understand the disease itself and the mechanisms of potential novel therapeutics. © 2021 The Authors. Current Protocols published by Wiley Periodicals LLC. Basic Protocol 1: End study protocols for tissue harvesting Basic Protocol 2: End study protocols for tissue processing Basic Protocol 3: Immunophenotyping using flow cytometry protocols Support Protocol: Tissue processing for cold storage Basic Protocol 4: Additional tissue processing for later analyses Basic Protocol 5: Analysis of serum auto-antibodies by ELISAs (ANAs, snRNP, and dsDNA).

Primary Immune Responses and Affinity Maturation Are Controlled by IgD

Mature B cells co-express IgM and IgD B cell antigen receptors (BCR) on their surface. While IgM BCR expression is already essential at early stages of development, the role of the IgD-class BCR remains unclear as most B cell functions appeared unchanged in IgD-deficient mice. Here, we show that IgD-deficient mice have an accelerated rate of B cell responsiveness as they activate antibody production within 24h after immunization, whereas wildtype (WT) animals required 3 days to activate primary antibody responses. Strikingly, soluble monovalent antigen suppresses IgG antibody production induced by multivalent antigen in WT mice. In contrast, IgD-deficient mice were not able to modulate IgG responses suggesting that IgD controls the activation rate of B cells and subsequent antibody production by sensing and distinguishing antigen-valences. Using an insulin-derived peptide we tested the role of IgD in autoimmunity. We show that primary autoreactive antibody responses are generated in WT and in IgD-deficient mice. However, insulin-specific autoantibodies were detected earlier and caused more severe symptoms of autoimmune diabetes in IgD-deficient mice as compared to WT mice. The rapid control of autoimmune diabetes in WT animals was associated with the generation of high-affinity IgM that protects insulin from autoimmune degradation. In IgD-deficient mice, however, the generation of high-affinity protective IgM is delayed resulting in prolonged autoimmune diabetes. Our data suggest that IgD is required for the transition from primary, highly autoreactive, to secondary antigen-specific antibody responses generated by affinity maturation.

Correlation between C-reactive Protein with Malondialdehyde in Systemic Lupus Erythematosus Patients

Systemic lupus erythematosus (SLE) is a systemic autoimmune disease characterized by an inflammatory process. One of the inflammation markers that can be measured is C-reactive protein (CRP). Another indicator of inflammation is malondialdehyde (MDA), though it is still uncommon to be analyzed in SLE patients. The study looked for the MDA value and found a correlation with CRP. A cross-sectional study design with a correlative analytical was performed. CRP level data was taken from Hasan Sadikin lupus registry data, and MDA levels were analyzed from a bioarchive patient's serum. We collected the patients' data who had CRP level from Hasan Sadikin lupus registry and analysed MDA levels from the serum sample. MDA levels were analyzed using an ELISA method. The data obtained were analyzed using the Pearson correlation and Eta correlation test. The study involved 78 data patients as subjects. It was found that the median of CRP and MDA was 0.85 mg/l and 153.10 ng/ml, respectively. These results indicate that the CRP levels in SLE patients are still within normal limits. Statistical analysis showed no correlation between CRP and MDA level (r = 0.2, P > 0.05). Additionally, the correlation between CRP and MDA with organ involvement, such as lupus nephritis (LN), lupus cutaneous (LC), and lupus musculoskeletal (LM), showed no correlation (F_h < F_t). There is no correlation between CRP and MDA levels in SLE patients, and specific organ involvement of the disease does not affect the correlation.

Naringenin mitigates autoimmune features in lupus-prone mice by modulation of T-cell subsets and cytokines profile

Naringenin is flavonoid mainly found in citrus fruits which has shown several biological properties. In this work, we evaluated the therapeutic potential of the flavonoid Naringenin. Five-month-old B6.MRL-Faslpr/J lupus-prone mice were administered daily orally with Naringenin for seven months. We showed that Naringenin treatment at 50 or 100 mg/kg inhibited the splenomegaly and decreased the levels of anti-nuclear and anti-dsDNA autoantibodies. Furthermore, a reduction in serum concentration of TNF-α, IFN-γ and IL-6 was observed in the mice provided with Naringenin. Interestingly, serum levels of IL-10 increased. Naringenin decreased the frequency and absolute numbers of splenic effector memory T cells. Additionally, in order to be able to evaluate whether Naringenin prevented kidney damage, twelve-week-old MRL/MpJ-Faslpr/J mice, an accelerated lupus model, were orally administered with Naringenin at 100 mg/kg for six weeks. Surprisingly, Naringenin treatment prevented kidney damage and reduced the development of fibrosis similar to cyclophosphamide group. Moreover, Naringenin treatment increased the percentage of regulatory T cells in this aggressive model of lupus. Together, these results suggest a potential ability of Naringenin to reduce the autoimmunity in lupus-prone mice by modulation of T-cell subsets and cytokines profile that mitigate the development of important lupus clinical manifestations.

Altered Tregs and oxidative stress in pregnancy associated lupus

AIM

SLE is a systemic autoimmune disease generally affecting woman in the reproductive age. It is associated with an altered level of Tregs and oxidative stress while an increase in Tregs, and different antioxidant mechanisms to combat oxidative stress are essential for successful pregnancy. Hence, this study aims to determine the level of CD4⁺ and CD8⁺ Tregs and oxidative stress in pregnant lupus patients.

METHODS

Ten healthy and 10 pregnant lupus volunteers from the North Indian population, within the age group of 20-30 years were enrolled in the study. All the patients were non-smokers, non-alcoholics and were not associated or undergoing therapy for any other disease. They had a SLEDAI of 37.4 ± 7.32 with 5.2 ± 1.93 years of disease duration. Oxidative stress was determined by measuring the enzyme activity of anti-oxidant enzymes (catalase, superoxide dismutase and glutathione peroxidase) and the level of reduced glutathione and lipids peroxidised, spectrophotometrically. Flowcytometry was performed for immunophenotyping to determine CD8⁺ and CD4⁺ Tregs.

RESULTS

Elevated CD8⁺ Tregs and diminished CD4⁺ Tregs were observed in pregnant lupus patients. Oxidative stress was significantly increased as the activities of anti-oxidant enzymes and level of reduced glutathione was considerably diminished. There was a substantial increase in the amount of lipids peroxidised.

CONCLUSION

Pregnant lupus patients undergo considerable level of oxidative stress in comparison to healthy pregnant woman. The decreased level of CD4⁺ Tregs and an increase in CD8⁺ Tregs might be another important factor responsible for pregnancy associated complications. Hence, lupus leads to alterations in the necessary conditions for a successful pregnancy, which might eventually cause higher mortality, morbidity and associated complications.

Chaperones may cause the focus of diabetes autoimmunity on distinct (pro)insulin peptides

It is still an enigma why T cell autoreactivity in type 1 diabetes targets few beta cell antigens only. Among these, one primary autoantigen is pro(insulin). Autoimmune T cells preferentially recognise three epitopes on the proinsulin molecule, of which the peptide region B:11-23 is the dominant one. Interestingly, the three regions superimpose with binding sites of the chaperone hsp70, the region B:11-23 being the strongest binding one. Absence of an intact core region B:15-17 prevents autoimmune diabetes in NOD as well as binding of hsp70. A role of hsp70 in selecting autoimmune epitopes is supported by the ability of this and other chaperones to deliver bound peptides to MHC class I and II molecules for efficient antigen presentation. Binding of hsp70 to receptors on antigen presenting cells such as TLR4 results in costimulatory signals for T cell activation. Strongest effects are seen for the mixture of hsp70 with the peptide B:11-23. Thus, hsp70 may assist in proinsulin epitope selection and efficient presentation to autoreactive T cells. The concept of chaperone guided immune reactivity may also apply to other autoimmune diseases.

Efficacy and Pharmacodynamic Modeling of the BTK Inhibitor Evobrutinib in Autoimmune Disease Models

Because of its role in mediating both B cell and Fc receptor signaling, Bruton's tyrosine kinase (BTK) is a promising target for the treatment of autoimmune diseases such as rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE). Evobrutinib is a novel, highly selective, irreversible BTK inhibitor that potently inhibits BCR- and Fc receptor-mediated signaling and, thus, subsequent activation and function of human B cells and innate immune cells such as monocytes and basophils. We evaluated evobrutinib in preclinical models of RA and SLE and characterized the relationship between BTK occupancy and inhibition of disease activity. In mouse models of RA and SLE, orally administered evobrutinib displayed robust efficacy, as demonstrated by reduction of disease severity and histological damage. In the SLE model, evobrutinib inhibited B cell activation, reduced autoantibody production and plasma cell numbers, and normalized B and T cell subsets. In the RA model, efficacy was achieved despite failure to reduce autoantibodies. Pharmacokinetic/pharmacodynamic modeling showed that mean BTK occupancy in blood cells of 80% was linked to near-complete disease inhibition in both RA and SLE mouse models. In addition, evobrutinib inhibited mast cell activation in a passive cutaneous anaphylaxis model. Thus, evobrutinib achieves efficacy by acting both on B cells and innate immune cells. Taken together, our data show that evobrutinib is a promising molecule for the chronic treatment of B cell-driven autoimmune disorders.

Pathways leading to an immunological disease: systemic lupus erythematosus

SLE is a chronic autoimmune disease caused by perturbations of the immune system. The clinical presentation is heterogeneous, largely because of the multiple genetic and environmental factors that contribute to disease initiation and progression. Over the last 60 years, there have been a number of significant leaps in our understanding of the immunological mechanisms driving disease processes. We now know that multiple leucocyte subsets, together with inflammatory cytokines, chemokines and regulatory mediators that are normally involved in host protection from invading pathogens, contribute to the inflammatory events leading to tissue destruction and organ failure. In this broad overview, we discuss the main pathways involved in SLE and highlight new findings. We describe the immunological changes that characterize this form of autoimmunity. The major leucocytes that are essential for disease progression are discussed, together with key mediators that propagate the immune response and drive the inflammatory response in SLE.

Metabolic Reprogramming Commits Differentiation of Human CD27+IgD+ B Cells to Plasmablasts or CD27-IgD- Cells

B cells play a crucial role in the pathogenesis of autoimmune diseases, such as systemic lupus erythematosus (SLE). However, the relevance of the metabolic pathway in the differentiation of human B cell subsets remains unknown. In this article, we show that the combination of CpG/TLR9 and IFN-α markedly induced the differentiation of CD27⁺IgD⁺ unswitched memory B cells into CD27^hiCD38^hi plasmablasts. The response was accompanied by mammalian target of rapamycin complex 1 (mTORC1) activation and increased lactate production, indicating a shift to glycolysis. However, CpG alone induced the differentiation of unswitched memory B cells into CD27^-IgD^- memory B cells with high cytokine production, but such differentiation was suppressed by IFN-α. AMP-activated protein kinase activation enhanced the differentiation to CD27^-IgD^- B cells, but it attenuated mTORC1 activation and differentiation into plasmablasts. High mTORC1 activation was noted in CD19⁺ B cells of patients with SLE and correlated with plasmablast differentiation and disease activity. Taken together, differential metabolic reprogramming commits the differentiation of human unswitched memory B cells into plasmablasts (the combination of CpG and IFN-α amplifies mTORC1-glycolysis pathways) or CD27^-IgD^- memory B cells (CpG alone amplifies the AMP-activated protein kinase pathway). The former metabolic pathway may play a pivotal role in SLE.

Mitochondrial Control and Guidance of Cellular Activities of T Cells

Immune cells protect us against infection and cancer cells, as well as functioning during healing processes to support tissue repairing and regeneration. These behaviors require that upon stimulation from immune activation the appropriate subsets of immune cells are generated. In addition to activation-induced signaling cascades, metabolic reprogramming (profound changes in metabolic pathways) also provides a novel form of regulation to control the formation of desirable immune responses. Immune cells encounter various nutrient compositions by circulating in bloodstream and infiltrating into peripheral tissues; therefore, proper engagement of metabolic pathways is critical to fulfill the metabolic demands of immune cells. Metabolic pathways are tightly regulated mainly via mitochondrial dynamics and the activities of the tricarboxylic acid cycle and the electron transport chain. In this review, we will discuss how metabolic reprogramming influences activation, effector functions, and lineage polarization in T cells, with a particular focus on mitochondria-regulated metabolic checkpoints. Additionally, we will further explore how in various diseases deregulation and manipulation of mitochondrial regulation can occur and be exploited. Furthermore, we will discuss how this knowledge can facilitate the design of immunotherapies.

Systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a chronic multisystem autoimmune disease that is highly heterogeneous in its presentation. This can pose significant challenges for physicians responsible for the diagnosis and treatment of such patients. SLE arises from a combination of genetic, epigenetic and environmental factors. Pathologically, the disease is primarily driven by loss of immune tolerance and abnormal B- and T-cell function. Major organ involvement may lead to significant morbidity and mortality. Classification criteria for SLE have been developed largely for research purposes; however, these are also widely used in clinical practice. Antinuclear antibodies are the hallmark serological feature, occurring in over 95% of patients with SLE at some point during their disease. The mainstay of treatment is antimalarial drugs such as hydroxychloroquine, combined with corticosteroids and conventional immunosuppressive drugs. An increasing understanding of pathogenesis has facilitated a move towards the development of targeted biologic therapies, with the introduction of rituximab and belimumab into clinical practice.

JAK3-STAT pathway blocking benefits in experimental lupus nephritis

Background

Lupus nephritis (LN) is a complex chronic autoimmune disease of unknown etiology characterized by loss of tolerance against several self-antigens. Cytokines are known to be central players in LN pathogenesis. The Janus kinase-signal transducer and activator of transcription (JAK-STAT) pathway is one important pathway that mediates signal transduction of several cytokines. In this study, we examined the pathogenic role of this pathway and how CP-690,550 treatment influences LN outcome.

Methods

Six-month-old NZB/NZWF1 mice were divided into two different treatment groups: (1) control animals given vehicle treatment, cyclophosphamide, and mycophenolate mofetil treatment as positive controls of the therapy and (2) mice treated with CP-690,550, a JAK3 inhibitor. Mice were treated for 12 weeks. We evaluated renal function, anti-double-stranded DNA (anti-dsDNA) antibody, renal histology changes, kidney complement and immunoglobulin G (IgG) deposits, T-cell and macrophage infiltration, kidney inflammatory gene expression, and circulating cytokine changes.

Results

CP-690,550 treatment significantly reduced proteinuria and improved renal function and histological lesions of the kidney. Compared with vehicle-treated animals, those undergoing CP-690,550 treatment showed significantly diminished anti-dsDNA antibody and complement component C3 and IgG deposition in glomeruli. We also observed a significant reduction of T-cell and macrophage infiltration. Kidney gene expression revealed a reduction in inflammatory cytokines and complement and related macrophage-attracting genes. Circulating inflammatory cytokines were also reduced with treatment.

Conclusions

On the basis of our results, we conclude that the JAK-STAT pathway is implicated in the progression of renal inflammation in NZB/WF1 mice and that targeting JAK3 with CP-690,550 is effective in slowing down the course of experimental LN. Thus, CP-690,550 could become a new therapeutic tool in LN and other autoimmune diseases.

Interleukin-6 receptor alpha blockade improves skin lesions in a murine model of systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is an autoimmune disease, characterized by antinuclear autoantibodies (ANA) and immunocomplexes, commonly affecting kidneys, skin, heart, lung or even the brain. We have shown that JunB(Δep) mice develop a SLE phenotype linked to increased epidermal Interleukin (IL)-6 secretion. Blocking of IL-6 receptor alpha (IL-6Rα) is considered as therapeutic strategy for the treatment of SLE. JunB(Δep) and wild-type mice were treated for short (5 weeks) or long term (21 weeks) with the IL-6Rα-blocking antibody MR16-1. Skin and kidney of mice were investigated by histology and immunofluorescence, and in addition, kidneys were analysed by electron microscopy. Furthermore, soluble IL-6R (sIL-6R), antihistone and antinucleosome antibodies levels were measured and associated with disease parameters. Treatment with MR16-1 resulted in significant improvement of SLE-like skin lesions in JunB(Δep) mice, compared to untreated mice. The sIL-6R amount upon long-term treatment with MR16-1 was significantly higher in JunB(Δep) versus untreated JunB(Δep) (P = 0.034) or wild-type mice (P = 0.034). MR16-1 treatment over these time spans did not significantly improve kidney pathology of immunoglobulin deposits causing impaired function. Significantly higher antihistone (P = 0.028) and antinucleosome antibody levels (P = 0.028) were measured in MR16-1-treated JunB(Δep) mice after treatment compared to levels before therapy. In conclusion, blockade of IL-6Rα improves skin lesions in a murine SLE model, but does not have a beneficial effect on autoimmune-mediated kidney pathology. Inhibition of IL-6R signalling might be helpful in lupus cases with predominant skin involvement, but combinatorial treatment might be required to restrain autoantibodies.

Infusion of Human Bone Marrow-Derived Mesenchymal Stem Cells Alleviates Autoimmune Nephritis in a Lupus Model by Suppressing Follicular Helper T-Cell Development

Systemic lupus erythematosus (SLE) is an autoimmune disease characterized by the production of autoantibodies to components of the cell nucleus. These autoantibodies are predominantly produced with the help of follicular helper T (Tfh) cells and form immune complexes that trigger widespread inflammatory damage, including nephritis. In recent studies, mesenchymal stem cells (MSCs) elicited diverse, even opposing, effects in experimental and clinical SLE. Here we investigated the effect of human bone marrow-derived MSCs (hBM-MSCs) in a murine model of SLE, the F1 hybrid between New Zealand Black and New Zealand White strains (NZB/W). We found that infusion of female NZB/W mice with hBM-MSCs attenuated glomerulonephritis; it also decreased levels of autoantibodies and the incidence of proteinuria and improved survival. These effects coincided with a decrease in Tfh cells and downstream components. Infiltration of long-lived plasma cells into the inflamed kidney was also reduced in the hBM-MSC-treated mice. Importantly, hBM-MSCs directly suppressed the in vitro differentiation of naive CD4(+) T cells toward Tfh cells in a contact-dependent manner. These results suggest that MSCs attenuate lupus nephritis by suppressing the development of Tfh cells and the subsequent activation of humoral immune components. They thus reveal a novel mechanism by which MSCs regulate humoral autoimmune diseases such as SLE.

Exonuclease TREX1 degrades double-stranded DNA to prevent spontaneous lupus-like inflammatory disease

The TREX1 gene encodes a potent DNA exonuclease, and mutations in TREX1 cause a spectrum of lupus-like autoimmune diseases. Most lupus patients develop autoantibodies to double-stranded DNA (dsDNA), but the source of DNA antigen is unknown. The TREX1 D18N mutation causes a monogenic, cutaneous form of lupus called familial chilblain lupus, and the TREX1 D18N enzyme exhibits dysfunctional dsDNA-degrading activity, providing a link between dsDNA degradation and nucleic acid-mediated autoimmune disease. We determined the structure of the TREX1 D18N protein in complex with dsDNA, revealing how this exonuclease uses a novel DNA-unwinding mechanism to separate the polynucleotide strands for single-stranded DNA (ssDNA) loading into the active site. The TREX1 D18N dsDNA interactions coupled with catalytic deficiency explain how this mutant nuclease prevents dsDNA degradation. We tested the effects of TREX1 D18N in vivo by replacing the TREX1 WT gene in mice with the TREX1 D18N allele. The TREX1 D18N mice exhibit systemic inflammation, lymphoid hyperplasia, vasculitis, and kidney disease. The observed lupus-like inflammatory disease is associated with immune activation, production of autoantibodies to dsDNA, and deposition of immune complexes in the kidney. Thus, dysfunctional dsDNA degradation by TREX1 D18N induces disease in mice that recapitulates many characteristics of human lupus. Failure to clear DNA has long been linked to lupus in humans, and these data point to dsDNA as a key substrate for TREX1 and a major antigen source in mice with dysfunctional TREX1 enzyme.

Disease activity in systemic lupus erythematosus correlates with expression of the transcription factor AT-rich-interactive domain 3A

OBJECTIVE

Systemic lupus erythematosus (SLE) is a complex and multifactorial autoimmune disease with striking clinical, immunologic, and genetic heterogeneity, despite nearly ubiquitous antinuclear antibody (ANA) production. Multiple gene polymorphisms have been associated with the disease, but these individually account for only a very small percentage of overall SLE risk. In earlier studies, constitutive expression of the DNA-binding protein AT-rich-interactive domain 3A (ARID3a) in transgenic mouse B lymphocyte lineage cells led to spontaneous ANA production and preferential development of B cells associated with production of polyreactive antibodies. Therefore, we undertook this study to determine whether ARID3a was overexpressed in B lymphocytes of SLE patients and whether ARID3a expression was associated with disease severity.

METHODS

A cross-section of SLE patients, rheumatoid arthritis patients, and age- and sex-matched controls was analyzed longitudinally for lupus disease activity, numbers of ARID3a+ peripheral blood mononuclear B cells from multiple B cell subsets, and immunoglobulin and cytokine levels.

RESULTS

Fifty of 115 SLE patients (43%) had dramatically increased numbers of ARID3a+ B cells compared to healthy controls. ARID3a was not expressed in naive B cells of healthy controls, but was abundant in these precursors of antibody-secreting cells in SLE patients. Total numbers of ARID3a+ B cells correlated with increased disease activity as defined by SLE Disease Activity Index scores in individuals assessed at 3 time points.

CONCLUSION

These findings identify B cell anomalies in SLE that allow stratification of patient samples based on ARID3a expression and implicate ARID3a as a potential marker of CD19+ B lymphocytes correlated with disease activity.

Systemic lupus erythematosus with hepatosplenic granuloma: a rare case

Background. Systemic lupus erythematosus (SLE) is an autoimmune disease which is known to present with a wide variety of clinical manifestations. Case Report. A 15-year-old male presented with complaints of moderate grade fever and generalized body swelling. There was no history of cough, weight loss, joint pain, oral ulcerations, skin rash, photosensitivity, loss of hair, pain abdomen, jaundice, or any significant illness in the past. Contrast enhanced computerized tomography of the abdomen revealed hypodense lesions in both liver and spleen (without contrast enhancement), suggestive of granulomas along with few retroperitoneal and mesenteric lymph nodes. On the basis of immunological tests and renal biopsy report, SLE with hepatosplenic granulomatosis diagnosis was made. He was given pulse methylprednisolone 500 mg, for 3 days and he showed dramatic improvement clinically. Conclusion. Hepatic and splenic granulomas are not common in SLE, but this should be kept in differential diagnosis.

Genetic variations in Toll-like receptors (TLRs 3/7/8) are associated with systemic lupus erythematosus in a Taiwanese population

Toll-like receptors (TLRs), as innate immunity sensors, play critical roles in immune responses. Six SNPs of TLR3, TLR7, and TLR8 were genotyped to determine their associations with systemic lupus erythematosus (SLE) and clinical manifestations of SLE. TLR7 SNP rs3853839 was independently associated with SLE susceptibility in females (G vs. C: p = 0.0051). TLR7 rs3853839-G (G vs. C: p = 0.0100) and TLR8 rs3764880-G (recessive model: p = 0.0173; additive model: p = 0.0161) were associated with pericardial effusion in females relative to healthy females. Anti-SSA positive cases were more likely to have the dominant TLR7 rs179010-T allele than normal controls (p = 0.0435). TLR3 rs3775296-T was associated with photosensitivity (p = 0.0020) and anemia (p = 0.0082). The “G-G” haplotype of TLR7 rs3853839 and TLR8 rs3764880 increased risk of SLE in females (age adjusted p = 0.0032). These findings suggest that TLR variations that modify gene expression affect risk for SLE susceptibility, clinical phenotype development, and production of autoantibodies.

Pivotal Functions of Plasmacytoid Dendritic Cells in Systemic Autoimmune Pathogenesis

Plasmacytoid dendritic cells (pDCs) were initially identified as the prominent natural type I interferon-producing cells during viral infection. Over the past decade, the aberrant production of interferon α/β by pDCs in response to self-derived molecular entities has been critically implicated in the pathogenesis of systemic lupus erythematosus and recognized as a general feature underlying other autoimmune diseases. On top of imperative studies on human pDCs, the functional involvement and mechanism by which the pDC-interferon α/β pathway facilitates the progression of autoimmunity have been unraveled recently from investigations with several experimental lupus models. This article reviews correlating information obtained from human in vitro characterization and murine in vivo studies and highlights the fundamental and multifaceted contribution of pDCs to the pathogenesis of systemic autoimmune manifestation.

Requirement for MyD88 signaling in B cells and dendritic cells for germinal center anti-nuclear antibody production in Lyn-deficient mice

The intracellular tyrosine kinase Lyn mediates inhibitory receptor function in B cells and myeloid cells, and Lyn(-/-) mice spontaneously develop an autoimmune and inflammatory disease that closely resembles human systemic lupus erythematosus. TLR-signaling pathways have been implicated in the production of anti-nuclear Abs in systemic lupus erythematosus and mouse models of it. We used a conditional allele of Myd88 to determine whether the autoimmunity of Lyn(-/-) mice is dependent on TLR/MyD88 signaling in B cells and/or in dendritic cells (DCs). The production of IgG anti-nuclear Abs, as well as the deposition of these Abs in the glomeruli of the kidneys, leading to glomerulonephritis in Lyn(-/-) mice, were completely abolished by selective deletion of Myd88 in B cells, and autoantibody production and glomerulonephritis were delayed or decreased by deletion of Myd88 in DCs. The reduced autoantibody production in mice lacking MyD88 in B cells or DCs was accompanied by a dramatic decrease in the spontaneous germinal center (GC) response, suggesting that autoantibodies in Lyn(-/-) mice may depend on GC responses. Consistent with this view, IgG anti-nuclear Abs were absent if T cells were deleted (TCRβ(-/-) TCRδ(-/-) mice) or if T cells were unable to contribute to GC responses as the result of mutation of the adaptor molecule SAP. Thus, the autoimmunity of Lyn(-/-) mice was dependent on T cells and on TLR/MyD88 signaling in B cells and in DCs, supporting a model in which DC hyperactivity combines with defects in tolerance in B cells to lead to a T cell-dependent systemic autoimmunity in Lyn(-/-) mice.

MicroRNA-let-7a promotes E2F-mediated cell proliferation and NFκB activation in vitro

Epigenetic factors, including altered microRNA (miRNA) expression, may contribute to aberrant immune cell function in systemic lupus erythematosus (SLE). MiRNA-let-7a (let-7a) has been shown to directly alter cell cycle progression and proinflammatory cytokine production. Due to the crucial role of let-7a in cell division and inflammation, we investigated let-7a-mediated proliferation and NFκB translocation in J774A.1 macrophages and MES 13 mesangial cells in vitro. In immune-stimulated cells transfected with let-7a, cell proliferation was significantly increased over time. There was a significant increase in the number of immune-stimulated cells in S and G2 phases. Immune-stimulated cells overexpressing let-7a had increased nuclear translocation of NFκB. Bioinformatical analysis revealed that the E2F family, critical regulators of the G1-S transition, has potential binding sites for let-7a in their mRNA transcripts. Let-7a overexpression significantly increased the expression of the cell cycle activator E2F2 and increased retinoblastoma protein (Rb) phosphorylation in immune-stimulated cells. The cell cycle inhibitor E2F5 was significantly decreased in let-7a-transfected cells that were immune-stimulated. Bioinformatical analysis revealed E2F2 and NFκB are transcription factors predicted to regulate the let-7a promoter. We analyzed transcriptional regulation of let-7a by real-time RT-PCR using chromatin immunoprecipitation with E2F2 and NFκB antibodies. There was an increase in E2F2 and NFκB binding in DNA enriched for the let-7a promoter in immune-stimulated cells. Silencing E2F2 or NFκB significantly decreased let-7a expression and IL-6 production in immune-stimulated cells. Taken together, our results suggest that overexpression of let-7a may contribute to hyperplasia and the proinflammatory response in SLE.

Autoantigens: novel forms and presentation to the immune system

It is clear that lupus autoimmunity is marked by a variety of abnormalities, including those found at a macroscopic scale, cells and tissues, as well as more microenvironmental influences, originating at the individual cell surface through to the nucleus. The convergence of genetic, epigenetic, and perhaps environmental influences all lead to the overt clinical expression of disease, reflected by the presences of autoantibodies and tissue pathology. This review will address several specific areas that fall among the non-genetic factors that contribute to lupus autoimmunity and related syndromes. In particular, we will discuss the importance of understanding various protein post-translational modifications (PTMs), mechanisms that mediate the ability of "modified self" to trigger autoimmunity, and how these PTMs influence lupus diagnosis. Finally, we will discuss altered pathways of autoantigen presentation that may contribute to the perpetuation of chronic autoimmune disease.

Systemic lupus erythematosus and granulomatous lymphadenopathy

BACKGROUND

Systemic lupus erythematosus (SLE) is known to present with a wide variety of clinical manifestations. Lymphadenopathy is frequently observed in children with SLE and may occasionally be the presenting feature. SLE presenting with granulomatous changes in lymph node biopsy is rare. These features may also cause diagnostic confusion with other causes of granulomatous lymphadenopathy.

CASE PRESENTATION

We report 12 year-old female who presented with generalized lymphadenopathy associated with intermittent fever as well as weight loss for three years. She also had developed anasarca two years prior to presentation. On presentation, she had growth failure and delayed puberty. Lymph node biopsy revealed granulomatous features. She developed a malar rash, arthritis and positive ANA antibodies over the course of next two months and showed WHO class II lupus nephritis on renal biopsy, which confirmed the final diagnosis of SLE. She was started on oral prednisolone and hydroxychloroquine with which her clinical condition improved, and she is currently much better under regular follow up.

CONCLUSION

Generalized lymphadenopathy may be the presenting feature of SLE and it may preceed the other symptoms of SLE by many years as illustrated by this patient. Granulomatous changes may rarely be seen in lupus lymphadenitis. Although uncommon, in children who present with generalized lymphadenopathy along with prolonged fever and constitutional symptoms, non-infectious causes like SLE should also be considered as a diagnostic possibility.

Selective inhibition of spleen tyrosine kinase (SYK) with a novel orally bioavailable small molecule inhibitor, RO9021, impinges on various innate and adaptive immune responses: implications for SYK inhibitors in autoimmune disease therapy

Introduction

Spleen tyrosine kinase (SYK) is a key integrator of intracellular signals triggered by activated immunoreceptors, including Bcell receptors (BCR) and Fc receptors, which are important for the development and function of lymphoid cells. Given the clinical efficacy of Bcell depletion in the treatment of rheumatoid arthritis and multiple sclerosis, pharmacological modulation of Bcells using orally active small molecules that selectively target SYK presents an attractive alternative therapeutic strategy.

Methods

A SYK inhibitor was developed and assayed in various in vitro systems and in the mouse model of collagen-induced arthritis (mCIA).

Results

A novel ATP-competitive inhibitor of SYK, 6-[(1R,2S)-2-Amino-cyclohexylamino]-4-(5,6-dimethyl-pyridin-2-ylamino)-pyridazine-3-carboxylic acid amide, designated RO9021, with an adequate kinase selectivity profile and oral bioavailability, was developed. In addition to suppression of BCR signaling in human peripheral blood mononuclear cells (PBMC) and whole blood, FcγR signaling in human monocytes, and FcϵR signaling in human mast cells, RO9021 blocked osteoclastogenesis from mouse bone marrow macrophages in vitro. Interestingly, Toll-like Receptor (TLR) 9 signaling in human Bcells was inhibited by RO9021, resulting in decreased levels of plasmablasts, immunoglobulin (Ig) M and IgG upon B-cell differentiation. RO9021 also potently inhibited type I interferon production by human plasmacytoid dendritic cells (pDC) upon TLR9 activation. This effect is specific to TLR9 as RO9021 did not inhibit TLR4- or JAK-STAT-mediated signaling. Finally, oral administration of RO9021 inhibited arthritis progression in the mCIA model, with observable pharmacokinetics (PK)-pharmacodynamic (PD) correlation.

Conclusions

Inhibition of SYK kinase activity impinges on various innate and adaptive immune responses. RO9021 could serve as a starting point for the development of selective SYK inhibitors for the treatment of inflammation-related and autoimmune-related disorders.

Fueling autoimmunity: type I interferon in autoimmune diseases

In recent years, active research using genomic, cellular and animal modeling approaches has revealed the fundamental forces driving the development of autoimmune diseases. Type I interferon imprints unique molecular signatures in a list of autoimmune diseases. Interferon is induced by diverse nucleic acid-containing complexes, which trigger innate immune activation of plasmacytoid dendritic cells. Interferon primes, activates or differentiates various leukocyte populations to promote autoimmunity. Accordingly, interferon signaling is essential for the initiation and/or progression of lupus in several experimental models. However, the heterogeneous nature of systemic lupus erythematosus requires better characterization on how interferon pathways are activated and subsequently promote the advancement of autoimmune diseases. Given the central role of type I interferon, various strategies are devised to target these cytokines or related pathways to curtail the progression of autoimmune diseases.

Inducible expression of kallikrein in renal tubular cells protects mice against spontaneous lupus nephritis

OBJECTIVE

To ascertain whether engineered expression of kallikreins within the kidneys, using an inducible Cre/loxP system, can ameliorate murine lupus nephritis.

METHODS

In mice with a lupus-prone genetic background, we engineered the expression of tamoxifen-inducible Cre recombinase under the control of a kidney-specific promoter whose activation initiates murine kallikrein-1 expression within the kidneys. These transgenic mice were injected with either tamoxifen or vehicle at age 2 months and then were monitored for 8 months for kallikrein expression and disease.

RESULTS

Elevated expression of kallikrein was detected in the kidney and urine of tamoxifen-injected mice but not in controls. At age 10 months, all vehicle-injected mice developed severe lupus nephritis, as evidenced by increased proteinuria (mean ± SD 13.43 ± 5.65 mg/24 hours), increased blood urea nitrogen (BUN) and serum creatinine levels (39.86 ± 13.45 mg/dl and 15.23 ± 6.89 mg/dl, respectively), and severe renal pathology. In contrast, the tamoxifen-injected mice showed significantly reduced proteinuria (6.6 ± 4.12 mg/24 hours), decreased BUN and serum creatinine levels (15.71 ± 8.17 mg/dl and 6.64 ± 3.39 mg/dl, respectively), and milder renal pathology. Tamoxifen-induced up-regulation of renal kallikrein expression increased nitric oxide production and dampened renal superoxide production and inflammatory cell infiltration, alluding to some of the pathways through which kallikreins may be operating within the kidneys.

CONCLUSION

Local expression of kallikreins within the kidney has the capacity to dampen lupus nephritis, possibly by modulating inflammation and oxidative stress.

Regulation of basement membrane-reactive B cells in BXSB, (NZBxNZW)F1, NZB, and MRL/lpr lupus mice

Autoantibodies to diverse antigens escape regulation in systemic lupus erythematosus under the influence of a multitude of predisposing genes. To gain insight into the differential impact of diverse genetic backgrounds on tolerance mechanisms controlling autoantibody production in lupus, we established a single lupus-derived nephritis associated anti-basement membrane Ig transgene on each of four inbred murine lupus strains, including BXSB, (NZBxNZW)F1, NZB, and MRL/lpr, as approved by the Duke University and the Durham Veterans Affairs Medical Centers' Animal Care and Use Committees. In nonautoimmune C57BL/6 mice, B cells bearing this anti-laminin Ig transgene are stringently regulated by central deletion, editing, and anergy. Here, we show that tolerance is generally intact in unmanipulated Ig transgenic BXSB, (NZBxNZW)F1, and NZB mice, based on absence of serum transgenic anti-laminin autoantibodies and failure to recover spontaneous anti-laminin monoclonal antibodies. Four- to six-fold depletion of splenic B cells in transgenic mice of these strains, as well as in MRL/lpr transgenic mice, and reduced frequency of IgM+ bone marrow B cells suggest that central deletion is grossly intact. Nonetheless the 4 strains demonstrate distinct transgenic B cell phenotypes, including endotoxin-stimulated production of anti-laminin antibodies by B cells from transgenic NZB mice, and in vitro hyperproliferation of both endotoxin- and BCR-stimulated B cells from transgenic BXSB mice, which are shown to have an enrichment of CD21-high marginal zone cells. Rare anti-laminin transgenic B cells spontaneously escape tolerance in MRL/lpr mice. Further study of the mechanisms underlying these strain-specific B cell fates will provide insight into genetic modification of humoral autoimmunity in lupus.

A diverse array of genetic factors contribute to the pathogenesis of systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a chronic systemic autoimmune disease with variable clinical presentation frequently affecting the skin, joints, haemopoietic system, kidneys, lungs and central nervous system. It can be life threatening when major organs are involved. The full pathological and genetic mechanisms of this complex disease are yet to be elucidated; although roles have been described for environmental triggers such as sunlight, drugs and chemicals, and infectious agents. Cellular processes such as inefficient clearing of apoptotic DNA fragments and generation of autoantibodies have been implicated in disease progression. A diverse array of disease-associated genes and microRNA regulatory molecules that are dysregulated through polymorphism and copy number variation have also been identified; and an effect of ethnicity on susceptibility has been described.

Treatment targets in systemic lupus erythematosus: biology and clinical perspective

Systemic lupus erythematosus (SLE) is a complex disease characterized by numerous autoantibodies and clinical involvement in multiple organ systems. The immunological events triggering the onset and progression of clinical manifestations are also complex and multi-step, including breach of tolerance in the adaptive immune system, amplification of autoimmunity through innate and adaptive immune system dysregulation, and end-organ damage. Studies of murine genetic manipulations and human risk variants have provided important clues to the cellular and molecular pathogenesis of SLE, operating at multiple of these steps. The breakdown of B-cell tolerance is probably a defining and early event in the disease process and may occur by multiple pathways, including alterations in factors that affect B-cell activation thresholds, B-cell longevity, and apoptotic cell processing. Examples of amplification of autoimmunity on the adaptive immune system side include disturbances in B-cell/T-cell collaboration. B cells can also amplify innate immune cell activation via antibody-dependent and antibody-independent mechanisms. Indeed, one of the key amplification loops in SLE is the activation of plasmacytoid dendritic cells via autoantibodies and RNA-containing and DNA-containing immune complexes, which act as Toll-like receptor ligands, stimulating the secretion of large quantities of IFNα. A more recent link between the innate and adaptive immune system in SLE includes the neutrophil, which can be primed by interferon and autoantibodies to release neutrophil extracellular traps as an additional source of immunogenic DNA, histones, and neutrophil proteins. The innate immune system activation then feeds back, driving autoreactive B-cell and T-cell survival and maturation. This self-perpetuating disease cycle creates the opportunity for targeted treatment inventions at multiple steps.

Contribution of Toll-like receptor signaling to germinal center antibody responses

Toll-like receptors (TLRs) have emerged as one of the most important families of innate immune receptors for initiating inflammation and also for promoting adaptive immune responses. Recent studies have examined the ability of TLRs to promote antibody responses, including T-cell-dependent antibody responses. Initial study suggested that TLR stimulation promotes primarily an extrafollicular antibody response, which rapidly produces moderate affinity antibodies made by short-lived plasma cells. Recent studies, however, have shown that TLRs can also enhance the germinal center response, which produces high affinity class-switched antibody made by long-lived plasma cells. TLR stimulation can increase the magnitude of the latter response and also enhance selection for high affinity IgG. This review summarizes recent advances in understanding the roles of TLRs in B cells and also in other cell types for enhancement of antibody responses, with an emphasis on T-cell-dependent and germinal center antibody responses.

Interferon-inducible Ifi200-family genes as modifiers of lupus susceptibility

Both genetic and environmental factors contribute to the development and progression of systemic lupus erythematosus (SLE), a complex autoimmune disease. The disease exhibits a strong gender bias and develops predominantly in females. Additionally, most SLE patients exhibit increased serum levels of interferon-α (IFN-α) and the "IFN signature". Studies using the mouse models of lupus have identified several lupus susceptibility loci, including the New Zealand Black (NZB)-derived autoimmunity 2 (Nba2) interval on the chromosome 1. The interval, which is syntenic to the human chromosome 1q region, harbors the FcγR family, SLAM/CD2-family, and the IFN-inducible Ifi200-family genes (encoding for the p200-family proteins). Studies involving the B6.Nba2 congenic mice revealed that the development of antinuclear autoantibodies (ANAs) depends on the age, gender, and activation of type I IFN-signaling. Interestingly, recent studies involving the generation of Nba2 subcongenic mouse lines and generation of mice deficient for the Fcgr2b or Aim2 gene within the interval have provided evidence that epistatic interactions among the Nba2 genes contribute to increased lupus susceptibility. Given that the expression of some of the p200-family proteins is differentially regulated by sex hormones and these proteins differentially regulate cytosolic DNA-induced production of type I IFN and proinflammatory cytokines (IL-1β and IL-18), the major known contributors of SLE-associated inflammation, we discuss the recent advancements in our understanding of the role of p200-family proteins in lupus susceptibility modification. An improved understanding of the role of p200-family proteins in the development of autoimmunity is likely to identify new approaches to treat SLE patients.

New therapeutic targets in systemic lupus

Glucocorticoids, aspirin, antimalarials and conventional immunosuppressants are the mainstay of treatment of Systemic Lupus Erythematosus (SLE). Until recently, the first three were the only agents approved for treatment. A better understanding of the pathophysiology of the immune system has identified new therapeutic targets. In fact, belimumab, a human monoclonal antibody to BLyS inhibitor has become, in recent months, the first drug approved for the treatment of SLE since 1957, underscoring difficulties of all kinds, including economic and organizational ones inherent to clinical trials on this disease. Many other molecules are in various stages of development and soon will have concrete results. In this review, we examined the mechanism of action and most relevant clinical data for these molecules.

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.