Genetic associations in type I interferon related pathways with autoimmunity

Baricitinib therapy response in rheumatoid arthritis patients associates to STAT1 phosphorylation in monocytes

Baricitinib is a Janus kinase (JAK) 1 and 2 inhibitor approved for treating rheumatoid arthritis (RA). The JAK/STAT system is essential in the intracellular signaling of different cytokines and in the activation process of the monocyte lineage. This study verifies the effects of baricitinib on STAT phosphorylation in monocytes of RA patients and evaluates the correlation between STAT phosphorylation and response to therapy. We evaluated the disease activity of patients (DAS28CRP) at baseline (T0) and after 4 and 12 weeks (T1–T3) of treatment with baricitinib, dividing them into responders (n = 7) and non-responders (n = 7) based on the reduction of DAS28CRP between T0 and T1 of at least 1.2 points. Through flow cytometry, STAT1 phosphorylation was analyzed at T0/T1/T3 in monocytes, at basal conditions and after IL2, IFNα, and IL6 stimulation. We showed that monocyte frequency decreased from T0 to T1 only in responders. Regarding the phosphorylation of STAT1, we observed a tendency for higher basal pSTAT1 in monocytes of non-responder patients and, after 4 weeks, a significant reduction of cytokine-induced pSTAT1 in monocytes of responders compared with non-responders. The single IFNα stimulation only partially recapitulated the differences in STAT1 phosphorylation between the two patient subgroups. Finally, responders showed an increased IFN signature at baseline compared with non-responders. These results may suggest that monocyte frequency and STAT1 phosphorylation in circulating monocytes could represent early markers of response to baricitinib therapy.

Type I Interferon and the Spectrum of Susceptibility to Viral Infection and Autoimmune Disease: A Shared Genomic Signature

Type I interferons (IFN-I) and their cognate receptor, the IFNAR1/2 heterodimer, are critical components of the innate immune system in humans. They have been widely explored in the context of viral infection and autoimmune disease where they play key roles in protection against infection or shaping disease pathogenesis. A false dichotomy has emerged in the study of IFN-I where interferons are thought of as either beneficial or pathogenic. This 'good or bad' viewpoint excludes more nuanced interpretations of IFN-I biology - for example, it is known that IFN-I is associated with the development of systemic lupus erythematosus, yet is also protective in the context of infectious diseases and contributes to resistance to viral infection. Studies have suggested that a shared transcriptomic signature underpins both potential resistance to viral infection and susceptibility to autoimmune disease. This seems to be particularly evident in females, who exhibit increased viral resistance and increased susceptibility to autoimmune disease. The molecular mechanisms behind such a signature and the role of sex in its determination have yet to be precisely defined. From a genomic perspective, several single nucleotide polymorphisms (SNPs) in the IFN-I pathway have been associated with both infectious and autoimmune disease. While overlap between infection and autoimmunity has been described in the incidence of these SNPs, it has been overlooked in work and discussion to date. Here, we discuss the possible contributions of IFN-Is to the pathogenesis of infectious and autoimmune diseases. We comment on genetic associations between common SNPs in IFN-I or their signalling molecules that point towards roles in protection against viral infection and susceptibility to autoimmunity and propose that a shared transcriptomic and genomic immunological signature may underlie resistance to viral infection and susceptibility to autoimmunity in humans. We believe that defining shared transcriptomic and genomic immunological signatures underlying resistance to viral infection and autoimmunity in humans will reveal new therapeutic targets and improved vaccine strategies, particularly in females.

Associations of gene polymorphisms in interferon-alpha signature-related genes with autoimmune thyroid diseases

Interferon (IFN)-α treatment predisposes patients to the occurrence of autoimmune thyroid disease (AITD).

METHODS

We investigated associations of single nucleotide polymorphisms (SNPs) of molecules participating in the IFN-α signature, including rs2304204 and rs2304206 of IFN regulatory factor 3 (IRF3), rs1061501 of IRF7, and rs7708392 of TNFA1P3-interacting protein 1 with serum IFN-α levels and AITD in an ethnic Chinese (ie Taiwanese) population. Totally, 319 patients with Graves' disease (GD), 83 patients with Hashimoto's thyroiditis (HT) and 351 healthy controls were recruited.

RESULTS

There were increased percentages of the C allele, and CC and TC + CC genotypes of rs1061501 in GD patients compared to the controls. HT patients had higher serum IFN-α levels compared to the controls, while there was no difference in serum IFN-α levels between patients with GD and controls. However, patients with GD in a remission status had lower serum IFN-α levels than those without remission. On the other hand, the C allele of rs1061501 was only associated with serum IFN-α levels in patients with HT.

CONCLUSIONS

The SNP rs1061501 of IRF7 was associated with the development of GD. Serum IFN-α levels were associated with HT, while they might modify the disease status of GD. Moreover, a genetic effect of rs1061501 on regulating serum IFN-α production was observed in HT.

Dynamics of the Type I Interferon Response During Immunosuppressive Therapy in Rheumatoid Arthritis

Objective: The type I interferon (IFN) response in rheumatoid arthritis (RA) has been extensively studied in relation to therapy with biological DMARDs (bDMARDs). However, the effect of conventional synthetic (cs)DMARDs and glucocorticoids (GCs) on IFN response gene (IRG) expression remains largely unknown, even though csDMARDS are used throughout all disease phases, including simultaneously with biologic therapy. This study was aimed to determine the dynamics of IFN response upon immunosuppressive treatment. Methods: Whole blood was collected in PAXgene tubes from 35 RA patients who received either COBRA therapy (combination of prednisone, initially 60 mg, methotrexate and sulfasalazine) (n = 14) or COBRA-light therapy (prednisone, initially 30 mg, and methotrexate) (n = 21). Expression of 10 IRGs was determined by real-time PCR at baseline (T0), after 4 weeks (T4), and 13 weeks (T13) of treatment. IRG selection was based on the differential presence of transcription factor binding sites (TFBS), in order to study the therapy effect on different pathway components involved in IFN signaling. Results: Seven of the 10 IRGs displayed significant changes during treatment (p ≤ 0.016). These 7 IRGs all displayed a particularly pronounced decrease between T0 and T4 (≥1.6-fold, p ≤ 0.0059). The differences between IRG sensitivity to the treatment appeared related to the presence of TFBS for STAT1 and IRF proteins within the genes. The extent of the decreases between T0 and T4 was similar for the COBRA- and COBRA-light-treated group, despite the differences in drug combination and doses in those groups. Between T4 and T13, however, IRG expression in the COBRA-light-treated group displayed a significant increase, whereas it remained stable or decreased even further in most COBRA-treated patients (comparison of mean fold changes, p = 0.011). A significant association between IRG dynamics and clinical response to therapy was not detected. Conclusions: Immunosuppressive treatment with csDMARDs, in this case a combination of prednisolone, methotrexate and sulfasalazine, substantially downregulates the IFN response in RA patients. The dynamics of this downregulation were partly dependent on the presence of TFBS within the IRGs and the combination and dosages of agents, but they were irrespective of the clinical response to therapy.

Checkpoint inhibitor-associated autoimmunity

Checkpoint inhibitors (CI) have revolutionized the management of many cancers but can result in immune-related adverse events (IRAE). In this chapter, we review the clinical manifestations and management of the most common IRAE, plus less common IRAE, such as inflammatory arthritis, of particular interest to rheumatologists. We review the mechanism of action of CI, predictors of IRAE, and the impact of IRAE on cancer outcomes. The study of IRAE is in its infancy; there are very few prospective studies and virtually no treatment trials. Where possible, we have drawn estimates of IRAE incidence from meta-analyses of randomized controlled trials. Clinical descriptions are derived from case series and case reports. Readers are encouraged to refer to consensus guidelines for IRAE management published by the American Society of Clinical Oncology and the Society for Immunotherapy of Cancer.

Immune response biomarkers in human and veterinary research

Biomarkers are increasingly utilised in biological research and clinical practice for diagnosis of disease, monitoring of therapeutic prognosis, or as end points in clinical studies. Cytokines are small molecules that orchestrate immune responses and as such have great potential as biomarkers for both human and veterinary fields. Given the ease of sampling in the blood, and their high prevalence in clinical applications we will focus on protein detection as an area for biomarker discovery. This is facilitated by new technological developments such as digital ELISA that have led to significant increases in sensitivity. Two highly relevant examples include type I interferons, namely IFNα, that is now directly quantifiable by digital ELISA from biological samples. The application of this approach to the study of the unique bat interferon response may reveal novel findings with applications in both human and veterinary research. As a second example we will describe the use of CXCL10 as a disease biomarker in Tuberculosis, highlighting findings from human and mouse studies that should be considered in veterinary research. In summary, we describe how cytokines may be applied as novel biomarkers and illustrate two key examples where human and veterinary research may complement each other in line with the One Health objectives.

MPA Modulates Tight Junctions' Permeability via Midkine/PI3K Pathway in Caco-2 Cells: A Possible Mechanism of Leak-Flux Diarrhea in Organ Transplanted Patients

Mycophenolic acid (MPA) is prescribed to prevent allograft rejection in organ transplanted patients. However, its use is sporadically linked to leak flux diarrhea and other gastrointestinal (GI) disturbances in around 75% of patients through yet unknown mechanisms. Recently, we identified Midkine as a modulator of tight junctions (TJs) permeability in MPA treated Caco-2 monolayer. In the present study, we investigated the possible involvement of Midkine dependent PI3K pathway in alteration of TJs under MPA treatment. Caco-2 cells were grown as monolayer to develop TJs and were treated for 72 h with DMSO (control) or MPA in presence and absence of Midkine inhibitor (iMDK) or PI3K inhibitors (LY/AMG). Caco-2 monolayer integrity was assessed by transepithelial electrical resistance (TEER) and FITC-dextran assays. Our functional assays showed that PI3K inhibitors (LY/AMG) can significantly inhibit the compromised TJs integrity of MPA-treated Caco-2 cells monolayer. Chromatin immunoprecipitation analyses showed a significant epigenetic activation of Midkine, PI3K, Cdx-2, and Cldn-2 genes and epigenetic repression of Cldn-1 gene after MPA treatment. The MPA-induced epigenetic alterations were further confirmed by mRNA and protein expression analysis. Collectively, our data shows that PI3K pathway as the downstream target of Midkine which in turn modulates p38MAPK and pAKT signaling to alter TJs permeability in Caco-2 cell monolayers treated with MPA. These results highlight the possible use of either Midkine or PI3K inhibitors as therapeutic agents to prevent MPA induced GI disturbances.

Omics studies: their use in diagnosis and reclassification of SLE and other systemic autoimmune diseases

Omics studies of systemic autoimmune diseases (SADs) in general, and SLE in particular, have delivered isolated information from transcriptome, epigenome, genome, cytokine and metabolome analyses. Such analyses have resulted in the identification of disease susceptibility genes and the description of IFN expression signatures, allowing extensive insight into the mechanisms of disease and the development of new therapies. Access to such technologies allows the recognition of patterns of disease at a pathway level, thereby, to reclassify SLE and other SADs and to develop new therapeutics from a personalized perspective. The use of omic information allows the discovery of correlative patterns involving drugs not currently suspected to be of value in SADs. In this review, we summarize the omics findings for SLE and propose ways of using the data for the identification of new biomarkers, finding new drugs and reclassifying patients not only with SLE, but also with other SADs.

Sequence analysis of TMEM173 exon 5 in patients with systemic autoimmune diseases

BACKGROUND

Overactivation of the interferon pathways has been demonstrated in patients suffering from different systemic autoimmune diseases (SADs). Genetic associations have been described for many genes involved in these pathways. Gain-of-function mutations in the TMEM173 gene have recently been reported in patients with autoinflammatory diseases that share some clinical features with SADs.

METHODS

We aimed at detecting the reported three mutations of transmembrane protein 173 (TMEM173) exon 5 in 100 patients suffering from: systemic lupus erythematosus (SLE) (n = 22), primary antiphospholipid syndrome (PAPS) (n = 20), systemic sclerosis (SSc) (n = 20), dermatomyositis (DM) (n = 20), and vasculitis (n = 18). Samples from 19 healthy controls were also included. Sequence analyses were performed from the derived TMEM173 exon 5 PCR fragment amplified from DNA obtained from whole blood.

RESULTS

Neither mutations nor single nucleotide polymorphisms (SNPs) in the exon 5 of the TMEM173 gene were detected. Just the rs7380272 SNP, located in the intronic region upstream exon 5, was detected in some patients and controls. The allele frequency of this SNP, though, was not statistically different between the patients groups and the control group.

CONCLUSIONS

Our study demonstrates the lack of association between the presence of SADs and mutations in exon 5 of the TMEM173 gene. SADs are complex multifactorial diseases in which not just one but probably many different genetic alterations may coexist. Although we cannot rule out the possibility that other variations may exist in other regions of this gene, we think that studies must be directed towards the analysis of other genes which, as TMEM173, also code for nucleic acid sensors that activate the nucleic-acid induced type I IFN pathway.

The DNA damage response and immune signaling alliance: Is it good or bad? Nature decides when and where

The characteristic feature of healthy living organisms is the preservation of homeostasis. Compelling evidence highlight that the DNA damage response and repair (DDR/R) and immune response (ImmR) signaling networks work together favoring the harmonized function of (multi)cellular organisms. DNA and RNA viruses activate the DDR/R machinery in the host cells both directly and indirectly. Activation of DDR/R in turn favors the immunogenicity of the incipient cell. Hence, stimulation of DDR/R by exogenous or endogenous insults triggers innate and adaptive ImmR. The immunogenic properties of ionizing radiation, a prototypic DDR/R inducer, serve as suitable examples of how DDR/R stimulation alerts host immunity. Thus, critical cellular danger signals stimulate defense at the systemic level and vice versa. Disruption of DDR/R-ImmR cross talk compromises (multi)cellular integrity, leading to cell-cycle-related and immune defects. The emerging DDR/R-ImmR concept opens up a new avenue of therapeutic options, recalling the Hippocrates quote "everything in excess is opposed by nature."

C1q-mediated repression of human monocytes is regulated by leukocyte-associated Ig-like receptor 1 (LAIR-1)

Systemic lupus erythematosus (SLE) is a chronic autoimmune disease characterized by abnormal function of both the innate and the adaptive immune system, leading to a loss of tolerance to self-antigens. Monocytes are a key component of the innate immune system and are efficient producers of multiple cytokines. In SLE, inappropriate activation of monocytes is thought to contribute to the loss of self-tolerance. In this study, we demonstrate that type 1 interferon (IFN) production by CpG-challenged monocytes can be suppressed by C1q through activating leukocyte-associated Ig-like receptor-1 (LAIR-1), which contains immunoreceptor tyrosine-based inhibition motifs (ITIMs). The phosphorylation of LAIR-1 and the interaction of LAIR-1 with SH2 domain-containing protein tyrosine phosphatase-1 (SHP-1) were enhanced after LAIR-1 engagement by C1q. Moreover, engagement of LAIR-1 by C1q inhibited nuclear translocation of interferon regulatory factor (IRF)-3 and IRF5 in CpG-stimulated monocytes. These data suggest a model in which LAIR-1 engagement by C1q helps maintain monocyte tolerance, specifically with respect to Toll-like receptor-9-mediated monocyte activation.

Genetics of ANCA-associated Vasculitides

The distribution of the anti-neutrophil cytoplasmic antibodies (ANCA)-associated vasculitides (AAV) is not uniform across geographical regions and ethnic and racial groups, suggesting that genetic and environmental factors affect the pathogenesis of these diseases. In addition, genetic factors affect not only the clinical syndrome phenotypes and their prognosis, but also ANCA specificity; these data suggest that AAV may need reclassification. Several genes have been evaluated, including ANCA targets and those of the immune system, for example co-stimulatory molecules, signaling regulators, cytokines, Fc and other receptors, and other proteins. This article provides a review of genetic factors affecting the pathogenesis and prognosis of AAV. Further studies to determine the effect of genetic factors on the clinical syndrome phenotypes and ANCA specificity need to be performed across different ethnic groups.

IRF5rs2004640 single nucleotide polymorphism is associated with susceptibility to rheumatoid arthritis in South Indian Tamils

Polymorphism of interferon regulatory factor 5 (IRF5), a latent transcription factor gene has been associated with various auto-immune diseases. Our aim was to study the IRF5rs2004640 gene polymorphism and its association with disease susceptibility, disease phenotype and treatment response in South Indian Tamil patients with rheumatoid arthritis (RA).The study was conducted on 217 RA patients fulfilling the American College of Rheumatology (ACR) 2010 criteria and 482 healthy controls (HCs) without family history of autoimmune disease. The IRF5rs2004640 genotyping was performed using a TaqMan 5' allelic discrimination assay. We found that the IRF5rs2004640T allele [P < 0.0001, odds ratio (OR) 3.25, 95% confidence interval (CI) 2.55-4.12] and TT genotype (P < 0.0001, OR 4.60, 95% CI 3.23-6.57) were significantly more frequent in RA patients as compared with HCs. No association was found between IRF5rs2004640 polymorphism, clinical manifestations, autoantibody profile and treatment response. IRF5rs2004640 T (mutant) allele may be a susceptibility factor conferring risk for RA in South Indian Tamils, whereas G allele (wild type) may be protective.

Dnase2a deficiency uncovers lysosomal clearance of damaged nuclear DNA via autophagy

Deficiencies in DNA-degrading nucleases lead to accumulation of self DNA and induction of autoimmunity in mice and in monogenic and polygenic human diseases. However, the sources of DNA and the mechanisms that trigger immunity remain unclear. We analyzed mice deficient for the lysosomal nuclease Dnase2a and observed elevated levels of undegraded DNA in both phagocytic and nonphagocytic cells. In nonphagocytic cells, the excess DNA originated from damaged DNA in the nucleus based on colocalization studies, live-cell imaging, and exacerbation by DNA-damaging agents. Removal of damaged DNA by Dnase2a required nuclear export and autophagy-mediated delivery of the DNA to lysosomes. Finally, DNA was found to accumulate in Dnase2a(-/-) or autophagy-deficient cells and induce inflammation via the Sting cytosolic DNA-sensing pathway. Our results reveal a cell-autonomous process for removal of damaged nuclear DNA with implications for conditions with elevated DNA damage, such as inflammation, cancer, and chemotherapy.

The contribution of epigenetics in Sjögren's Syndrome

Sjögren’s syndrome (SS) is a chronic autoimmune epithelitis that combines exocrine gland dysfunctions and lymphocytic infiltrations. While the pathogenesis of SS remains unclear, its etiology is multifunctional and includes a combination of genetic predispositions, environmental factors, and epigenetic factors. Recently, interest has grown in the involvement of epigenetics in autoimmune diseases. Epigenetics is defined as changes in gene expression, that are inheritable and that do not entail changes in the DNA sequence. In SS, several epigenetic mechanisms are defective including DNA demethylation that predominates in epithelial cells, an abnormal expression of microRNAs, and abnormal chromatin positioning-associated with autoantibody production. Last but not least, epigenetic modifications are reversible as observed in minor salivary glands from SS patients after B cell depletion using rituximab. Thus epigenetic findings in SS open new perspectives for therapeutic approaches as well as the possible identification of new biomarkers.

Research in practice: the impact of interferon-α therapy on immune tolerance

Interferon-α (IFN-α) is the only drug approved for adjuvant therapy of malignant melanoma and is also used in the treatment of hematological and solid tumors. Along with its proven clinical efficacy, IFN-α produces several side effects, particularly with regard to autoimmune disorders. Curious about symptoms of autoimmunity during IFN-α therapy, we asked whether IFN-α directly impacts on immune tolerance. We found that IFN-α does alter the function of tolerogenic dendritic cells (DC) as well as of induced and naturally occurring T-regulatory cells (nTregs). IFN-α blocks the tolerogenic phenotype of DC by inducing maturation and thus preventing the induction of inducible Tregs by DC. It also has direct effects on nTregs. IFN-α reduces cAMP in Tregs via ERK/phosphodiesterase-mediated pathways. Since cAMP is essentially involved in suppression by nTregs, the IFN-α-dependent reduction of cAMP levels abolishes the suppressive capacity of nTregs. Therefore, Tregs are incapable of suppressing the activity of effector T cells and natural killer cells, resulting in tumor rejection. Thus, IFN-α overcomes immunological tolerance processes, leading to an improved immunostimulation and efficient tumor rejection, but also increases the risk of autoimmunity.

Twins discordant for myositis and systemic lupus erythematosus show markedly enriched autoantibodies in the affected twin supporting environmental influences in pathogenesis

Background

Studies of twin pairs discordant for autoimmune conditions provide a unique opportunity to explore contributing factors triggered by complex gene-environment interactions.

Methods

In this cross-sectional study, thirty-one monozygotic or dizygotic twin pairs discordant for myositis or systemic lupus erythematosus (SLE), along with matched healthy controls were evaluated for antibodies against a panel of 21 autoantigens.

Results

Autoantibody profiling revealed that 42% of the affected twins showed significant seropositivity against autoantigens in the panel. In many of these affected twins, but none of healthy controls, there were high levels of autoantibodies detected against two or more autoantigens commonly seen in systemic autoimmune diseases including Ro52, Ro60, RNP-70 K and/or RNP-A. In contrast, only 10% (3/31) of the unaffected twins showed seropositivity and these immunoreactivities were against single autoantigens not seen in systemic autoimmune diseases. While no significant differences in autoantibodies were detected between the affected or unaffected twins against thyroid peroxidase, transglutaminase and several cytokines, 23% of the affected twins with myositis showed autoantibodies against the gastric ATPase. Analysis of the monozygotic twins separately also revealed a higher frequencies of autoantibodies in the affected twins compared to the unaffected twins (P = 0.046). Lastly, clinical analysis of both the affected monozygotic and dizygotic twins revealed that the autoantibody seropositive affected twins had a greater global disease activity score compared to seronegative affected twins (P = 0.019).

Conclusion

The findings of significantly more autoantibodies in the affected twins with myositis and SLE compared to the unaffected twins are consistent with potential non-genetic factors playing a role in autoantibody production and pathogenesis of these autoimmune disorders.

A functional variant in microRNA-146a promoter modulates its expression and confers disease risk for systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a complex autoimmune disease with a strong genetic predisposition, characterized by an upregulated type I interferon pathway. MicroRNAs are important regulators of immune homeostasis, and aberrant microRNA expression has been demonstrated in patients with autoimmune diseases. We recently identified miR-146a as a negative regulator of the interferon pathway and linked the abnormal activation of this pathway to the underexpression of miR-146a in SLE patients. To explore why the expression of miR-146a is reduced in SLE patients, we conducted short parallel sequencing of potentially regulatory regions of miR-146a and identified a novel genetic variant (rs57095329) in the promoter region exhibiting evidence for association with SLE that was replicated independently in 7,182 Asians (P(meta) = 2.74×10(-8), odds ratio = 1.29 [1.18-1.40]). The risk-associated G allele was linked to reduced expression of miR-146a in the peripheral blood leukocytes of the controls. Combined functional assays showed that the risk-associated G allele reduced the protein-binding affinity and activity of the promoter compared with those of the promoter containing the protective A allele. Transcription factor Ets-1, encoded by the lupus-susceptibility gene ETS1, identified in recent genome-wide association studies, binds near this variant. The manipulation of Ets-1 levels strongly affected miR-146a promoter activity in vitro; and the knockdown of Ets-1, mimicking its reduced expression in SLE, directly impaired the induction of miR-146a. We also observed additive effects of the risk alleles of miR-146a and ETS1. Our data identified and confirmed an association between a functional promoter variant of miR-146a and SLE. This risk allele had decreased binding to transcription factor Ets-1, contributing to reduced levels of miR-146a in SLE patients.

Pathogen recognition receptor signaling accelerates phosphorylation-dependent degradation of IFNAR1

An ability to sense pathogens by a number of specialized cell types including the dendritic cells plays a central role in host's defenses. Activation of these cells through the stimulation of the pathogen-recognition receptors induces the production of a number of cytokines including Type I interferons (IFNs) that mediate the diverse mechanisms of innate immunity. Type I IFNs interact with the Type I IFN receptor, composed of IFNAR1 and IFNAR2 chains, to mount the host defense responses. However, at the same time, Type I IFNs elicit potent anti-proliferative and pro-apoptotic effects that could be detrimental for IFN-producing cells. Here, we report that the activation of p38 kinase in response to pathogen-recognition receptors stimulation results in a series of phosphorylation events within the IFNAR1 chain of the Type I IFN receptor. This phosphorylation promotes IFNAR1 ubiquitination and accelerates the proteolytic turnover of this receptor leading to an attenuation of Type I IFN signaling and the protection of activated dendritic cells from the cytotoxic effects of autocrine or paracrine Type I IFN. In this paper we discuss a potential role of this mechanism in regulating the processes of innate immunity.

Genetics and genomics of Sjögren's syndrome: research provides clues to pathogenesis and novel therapies

PURPOSE

Although the key inciting events that drive the progression from autoantibodies to clinical disease remain to be clarified, new light has been shed on the factors contributing to disease susceptibility and the role of genetic factors in determining Sjögren's syndrome (SS) disease phenotypes. The purpose of this article is to provide an update on the role of genetic markers in the susceptibility to and pathogenesis of SS. This article also discusses how genomic and proteomic technology can help in the design of specific therapeutics.

KEY FINDINGS

Recent evidence suggests that inflammatory genes associated with interferon pathways, and specific regulatory genes that control the maturation and proliferation of B cells, contribute to the pathogenesis of SS. Both gene expression profiling technology and gene association studies have been used to identify these key biological pathways. Molecularly, defined subsets of pSS patients are also being revealed by these studies. Previously, identified gene loci that predispose to multiple autoimmune disorders have been confirmed supporting the paradigm of "general" autoimmune disease genes. Association of SS with many additional susceptibility loci are likely to be established through ongoing genome-wide association scans (GWAS). Clues from genetic studies suggest that targeting B cells will prove to be an effective way of reducing the systemic manifestations of pSS and are supported by early clinical trials.

SUMMARY

Genome-wide technologies are likely to identify new genes and molecular pathways in the pathogenesis of SS that will be useful not only to identify patients at risk for SS, but also to identify subsets of patients at risk for variable levels of disease severity. In the future, these studies could identify novel biomarkers that will lead to significant advances in management by providing the means to tailor therapeutic strategies to individual patients.

Genetic predisposition to autoimmunity--what have we learned?

Rapid advances in genetic technologies have led to the identification of more than 85 loci that contribute to susceptibility to autoimmune diseases. These susceptibility genes are distributed throughout the innate and adaptive immune systems, indicating that dysregulations in both immune systems participate in the development of autoimmunity. A significant subset of these susceptibility genes are shared between multiple autoimmune diseases. However, the dysregulation of specific pathways, such as the pathogen recognition receptors of the innate immune system and the TNF supergene family, are significantly involved in some autoimmune diseases. Although these findings dramatically increase the details available concerning the nature of genetic predisposition to autoimmunity, a mechanistic understanding of the processes involved has not been achieved. Future studies must focus on correlating phenotypes with specific genotypes to improve our understanding of the immune processes that are dysregulated during the development of autoimmunity.