Risk Factor For Systemic Lupus Erythematosus Research Articles

Current views on etiopathogenesis of systemic lupus erythematosus

The article is a review of information concerning etiopathogenesis of systemic lupus erythematosus (SLE). Due to the risk of serious complications, including death, the clarification of etiology could result in substantial improvement or even complete cure of the disease. Progress in scientific research of observed disorder mechanisms together with implementation of appropriate therapies contributed to a higher detection rate, improved course and decreased mortality in SLE. However, there are still many doubts, which legitimate the need of further research. A significant role in development of the disease and further exacerbations is played by environmental factors. Therefore, decreased exposure to UV light, female sex hormone and microbial antigens is associated with improved course and decreased frequency of exacerbations. Less is known about the genetic basis of SLE, which results from a multigene disease background and complex hereditary mechanisms. It is estimated that the disease may be conditioned by around 100 genes, that only in part are functionally determined. Only part of them is already functionally characterized. The role played by most of them is still unknown. Research currently being conducted is aimed at detecting genetic polymorphism in large and genetically diverse populations. It will allow evaluation of the role of a particular gene in protein biosynthesis, which is responsible for development of regulatory process disturbances, commonly observed in the course of SLE. The article presents current directions of research and the latest advances in epidemiology as well as environmental and genetic risk factors of SLE.

Systemic lupus erythematosus risk factors for coronary artery calcifications

Premature atherosclerosis in patients with SLE is partially explained by traditional risk factors; therefore, we aimed to identify lupus-related risk factors for coronary artery calcifications. An inception cohort of 139 lupus patients (93% females) was screened for coronary artery calcifications using Multidetector CT, after 5.1 years of follow-up. Clinical and immunological variables and cardiovascular risk factors were assessed longitudinally. Also, 100 age- and sex-matched healthy subjects were studied. Correlates for calcifications were analysed in lupus patients, including levels of lipids and inflammatory molecules in samples obtained at enrolment, mid-term follow-up and at screening. At enrolment, lupus patients were 27.2 (9.1) years of age and with a disease duration of 5.4 (3.8) months. Calcifications were detected in 7.2% of patients and 1% of controls [unadjusted odds ratio (OR) 7.7, 95% CI 1.05, 336.3, P = 0.02]. In lupus, calcifications were detected since the age of 23 years and from 3 years of diagnosis. Patients with calcifications were older, post-menopausal, and had higher levels of serum apolipoprotein B and Framingham risk scores (P < 0.05). Lupus-related factors identified included age at diagnosis, IgG aCLs, cumulative lupus activity, length of moderate/severe activity and cumulative dose of prednisone and CYC (P < 0.05). Use of anti-malarials was protective (P = 0.006). Logistic regression analysis showed as predictors of calcification: disease duration (OR 15.1, 95% CI 2.6, 87.2), age at enrolment (OR 8.5, 95% CI 1.7, 43.0) and SLEDAI 2000 update (SLEDAI-2K) mean area under the curve (OR 12.3, 95% CI 2.5, 61.8). Longitudinal analyses of lipids and inflammatory molecules did not differ between patients. Disease activity is a potentially modifiable risk factor for coronary artery calcifications in SLE. Therefore, management of traditional risk factors plus tight control of lupus activity, including the use of anti-malarials, is recommended.

Interferon Alpha as a Primary Pathogenic Factor in Human Lupus

Interferon alpha (IFN-α) is a critical mediator of human systemic lupus erythematosus (SLE). This review will summarize evidence supporting the role for IFN-α in the initiation of human SLE. IFN-α functions in viral immunity at the interface of innate and adaptive immunity, a position well suited to setting thresholds for autoimmunity. Some individuals treated with IFN-α for chronic viral infections develop de novo SLE, which frequently resolves when IFN-α is withdrawn, supporting the idea that IFN-α was causal. Abnormally high IFN-α levels are clustered within SLE families, suggesting that high serum IFN-α is a heritable risk factor for SLE. Additionally, SLE-risk genetic variants in the IFN-α pathway are gain of function in nature, resulting in either higher circulating IFN-α levels or greater sensitivity to IFN-α signaling in SLE patients. A recent genome-wide association study has identified additional novel genetic loci associated with high serum IFN-α in SLE patients. These data support the idea that genetically determined endogenous elevations in IFN-α predispose to human SLE. It is possible that some of these gain-of-function polymorphisms in the IFN-α pathway are useful in viral defense, and that risk of SLE is a burden we have taken on in the fight to defend ourselves against viral infection.

Confirmation of C4 gene copy number variation and the association with systemic lupus erythematosus in Chinese Han population

The distribution of complement component 4 (C4) gene copy number (GCN) has been validated in European populations. Meanwhile, C4 gene has been identified as a susceptibility gene for systemic lupus erythematosus (SLE). However, the association and the possible phenotype significance remain to be determined intensely in the Chinese population. This study was designed to validate the distribution of C4 GCNs in Chinese Han and the correlation between C4 GCNs and SLE using quantitative real-time polymerase chain reaction in 924 SLE patients and 1,007 controls. The results presented distribution of C4 GCNs in healthy populations and also showed that lower C4 GCN was a risk factor for SLE and higher C4 GCN was a protective factor against the disease susceptibility, which was similar to the report in the Caucasian population. Furthermore, we found the association between C4A GCN and disease subphenotypes of arthritis with SLE. We conclude that the association of C4 GCN with SLE was replicated in Chinese Han population, which highlighted the importance of C4 in SLE pathogenesis of diverse populations.

MHC region and risk of systemic lupus erythematosus in African American women.

The major histocompatibility complex (MHC) on chromosome 6p21 is a key contributor to the genetic basis of systemic lupus erythematosus (SLE). Although SLE affects African Americans disproportionately compared to European Americans, there has been no comprehensive analysis of the MHC region in relationship to SLE in African Americans. We conducted a screening of the MHC region for 1,536 single nucleotide polymorphisms (SNPs) and the deletion of the C4A gene in a SLE case-control study (380 cases, 765 age-matched controls) nested within the prospective Black Women's Health Study. We also genotyped 1,509 ancestral informative markers throughout the genome to estimate European ancestry to control for population stratification due to population admixture. The most strongly associated SNP with SLE was the rs9271366 (odds ratio, OR = 1.70, p = 5.6 × 10(-5)) near the HLA-DRB1 gene. Conditional haplotype analysis revealed three other SNPs, rs204890 (OR = 1.86, p = 1.2 × 10(-4)), rs2071349 (OR = 1.53, p = 1.0 × 10(-3)), and rs2844580 (OR = 1.43, p = 1.3 × 10(-3)), to be associated with SLE independent of the rs9271366 SNP. In univariate analysis, the OR for the C4A deletion was 1.38, p = 0.075, but after simultaneous adjustment for the other four SNPs the odds ratio was 1.01, p = 0.98. A genotype score combining the four newly identified SNPs showed an additive risk according to the number of high-risk alleles (OR = 1.67 per high-risk allele, p < 0.0001). Our strongest signal, the rs9271366 SNP, was also associated with higher risk of SLE in a previous Chinese genome-wide association study (GWAS). In addition, two SNPs found in a GWAS of European ancestry women were confirmed in our study, indicating that African Americans share some genetic risk factors for SLE with European and Chinese subjects. In summary, we found four independent signals in the MHC region associated with risk of SLE in African American women.

Systemic lupus erythematosus.

Systemic lupus erythematosus (SLE) is one of the most diverse autoimmune diseases as it may affect any organ in the body and display a broad spectrum of clinical and immunological manifestations. Epidemiological studies have identified marked differences in the prevalence and course of SLE between genders, and across different ages, races and geographic locations. Methodological differences between studies may account for some of the disparity seen. Additionally, some insights into possible environmental risk factors for SLE have also been provided. As this condition is relatively uncommon, multifactorial, and largely influenced by genetic predisposition, it is inherently difficult to confirm or exclude infectious or environmental contributors to its etiology. Movement of people between communities and defining specific exposures can also be problematic. Despite these limitations, ongoing observation of SLE cohorts in multiple countries and settings, along with large international cooperative efforts in recent years, have helped clarify the risks of SLE in various groups and have defined marked differences in the worldwide occurrence of the disease.

The Potential Role of Interferon-regulatory Factor 7 Among Taiwanese Patients with Systemic Lupus Erythematosus

Type I interferons (IFN), especially IFN-α, have been proposed to underlie the pathogenesis of systemic lupus erythematosus (SLE). Members of the IFN regulatory factor (IRF) family, which regulate IFN expression, have been implicated as risk factors for SLE. Our aims were to investigate the expression of IRF7 and its correlation with disease activity and to explore the association in Taiwanese patients between 2 genetic single-nucleotide polymorphisms (SNP) of IRF7 and SLE. IRF7 messenger RNA (mRNA) levels were measured in peripheral blood mononuclear cells by real-time reverse transcription polymerase chain reaction in 51 adult patients with SLE and 65 age-matched and sex-matched controls. Their serum IFN-α levels were determined by ELISA and the clinical manifestations were recorded at the same time. Two IRF7 SNP, rs1061501 and rs1061502, were examined by genotyping across 92 patients with SLE and 92 age and sex-matched healthy control subjects. Compared with controls, the expression of IRF7 mRNA was significantly increased in patients with SLE and was positively correlated with both the serum level of IFN-α and lupus disease activity. The distribution of SNP rs1061501 by genotype (CC, CT, and TT) and by allele (C, T) was significantly different between the SLE and the control group (p = 0.028 for genotype and p = 0.009 for allele). There were no significant differences for SNP rs1061502. The results suggest that dysregulation of IRF7 might mediate an excessive production of IFN-α, which then exerts a crucial effect on the pathogenesis of human SLE. The IRF7 SNP rs1061501 TT genotype and T allele are enriched in Taiwanese patients with SLE and thus would seem to be associated with an increased risk of developing SLE.

TNF promoter -308 G&gt;A and LTA 252 A&gt;G polymorphisms in Portuguese patients with systemic lupus erythematosus

The polymorphism of the tumor necrosis factor (TNF) promoter gene at position -308 and that of the lymphotoxin alpha (LTA) gene at position 252 have been implicated as genetic risk factors for systemic lupus erythematosus (SLE) in some populations. In a nested case-control study, we investigated the possible association of these polymorphisms with susceptibility to SLE and with phenotypic disease features in Portuguese Caucasian patients. TNF-308 G>A and LTA 252 A>G polymorphisms were determined by restriction fragment length polymorphism analysis in a cohort of 115 SLE patients and 152 unrelated healthy controls, and the magnitude of the association between genotypes and SLE diagnosis was calculated. For SLE patients, we also tested the association between disease characteristics and genotypes. No significant differences in genotype or allele frequencies could be identified between SLE cases and controls. Lupus nephritis (OR = 2.84; 95%CI 1.14-7.03, P = 0.02) and the presence of anti-Sm antibodies (OR = 3.11; 95%CI 1.08-8.94; P = 0.03) were significantly more prevalent among lupus patients possessing the TNF-308 A allele. The occurrence of nephritis was also higher in LTA 252 G allele carriers (OR = 2.90; 95%CI 1.12-7.54; P = 0.02). Our results do not support a major role of either the TNF-308 G>A or the LTA 252 A>G polymorphisms as genetic risk factors for SLE. Nevertheless, these polymorphisms appear to associate with the risk of renal lupus and distinct immunological features.

Replicated associations of TNFAIP3, TNIP1 and ETS1 with systemic lupus erythematosus in a southwestern Chinese population

IntroductionRecent genome-wide and candidate gene association studies in large numbers of systemic lupus erythematosus (SLE) patients have suggested approximately 30 susceptibility genes. These genes are involved in three types of biological processes, including immune complex processing, toll-like receptor function and type I interferon production, and immune signal transduction in lymphocytes, and they may contribute to the pathogenesis of SLE. To better understand the genetic risk factors of SLE, we investigated the associations of seven SLE susceptibility genes in a Chinese population, including FCGR3A, FCGR2A, TNFAIP3, TLR9, TREX1, ETS1 and TNIP1.MethodsA total of 20 SNPs spanning the seven SLE susceptibility genes were genotyped in a sample of 564 unrelated SLE patients and 504 unrelated healthy controls recruited from Yunnan, southwestern China. The associations of SNPs with SLE were assessed by statistical analysis.ResultsFive SNPs in two genes (TNFAIP3 and ETS1) were significantly associated with SLE (corrected P values ranging from 0.03 to 5.5 × 10-7). Through stratified analysis, TNFAIP3 and ETS1 showed significant associations with multiple SLE subphenotypes (such as malar rash, arthritis, hematologic disorder and antinuclear antibody) while TNIP1 just showed relatively weak association with onset age. The associations of the SNPs in the other four genes were not replicated.ConclusionsThe replication analysis indicates that TNFAIP3, ETS1 and TNIP1 are probably common susceptibility genes for SLE in Chinese populations, and they may contribute to the pathogenesis of multiple SLE subphenotypes.

Systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is one of the most diverse autoimmune diseases as it may affect any organ in the body and display a broad spectrum of clinical and immunological manifestations. Epidemiological studies have identified marked differences in the prevalence and course of SLE between genders, and across different ages, races and geographic locations. Methodological differences between studies may account for some of the disparity seen. Additionally, some insights into possible environmental risk factors for SLE have also been provided. As this condition is relatively uncommon, multifactorial, and largely influenced by genetic predisposition, it is inherently difficult to confirm or exclude infectious or environmental contributors to its etiology. Movement of people between communities and defining specific exposures can also be problematic. Despite these limitations, ongoing observation of SLE cohorts in multiple countries and settings, along with large international cooperative efforts in recent years, have helped clarify the risks of SLE in various groups and have defined marked differences in the worldwide occurrence of the disease.

A targeted association study in systemic lupus erythematosus identifies multiple susceptibility alleles

Systemic lupus erythematosus (SLE) is a multisystem autoimmune disease. Multiple genetic and environmental factors contribute to the pathogenesis of this disease. Recent genome-wide association studies have added substantially to the number of genes associated with SLE. To replicate some of these susceptibility loci, single-nucleotide polymorphisms reported to be associated to SLE were evaluated in a cohort of 245 well-phenotyped Canadian SLE trios. Our results replicate previously reported associations to alleles of interferon regulatory factor 5 (IRF5), major histocompatibility complex (MHC), tumor necrosis factor (ligand) superfamily member 4 (TNFSF4), Kell blood group complex subunit-related family member 6 (XKR6), B-cell scaffold protein with ankyrin repeats 1 (BANK1), protein tyrosine phosphatase non-receptor type 22 (PTPN22), ubiquitin-conjugating enzyme E2L 3 (UBE2L3) and islet cell autoantigen 1 (ICA1). We also identify putative associations to cytotoxic T-lymphocyte-associated protein 4 (CTLA4), a gene associated with several autoimmune disorders, and ERBB3, a locus on 12q13 that was previously reported to be associated with type 1 diabetes. This study confirms the existence of multiple genetic risk factors for SLE, and supports the notion that some risk factors for SLE are shared with other inflammatory disorders.

Current advances in lupus genetic and genomic studies in Asia

The genetic components in systemic lupus erythematosus (SLE) have long been established, however, it has been unclear for many years whether the same genetic risk factors for SLE are shared across different ethnic groups. Over the past few years, a number of genetic and genomic studies have been conducted in Asian populations to address this question. These studies have demonstrated that genetic heterogeneity does exist in SLE across different ethnic groups. With these studies, it has been established that a number of genes associated with SLE in Caucasians are also risk factors in Asians: HLA class II genes, STAT4, BANK1, BLK, IRF5, TNFSF4, ITGAM, etc., while there are also novel genetic risk factors identified by these studies in Asians, for instance, the ETS1 and WDFY4 in Chinese. For the genomic studies, the interferon signature has been confirmed as a major lupus molecular phenotype in Asians the same as in Caucasians; microRNA expression profiling and its novel role in regulating the interferon pathway has been first revealed in Asians. Further understanding of the function of lupus disease genes and delineating the key molecular pathway(s) will enhance the development of novel therapeutic targets and biomarkers for individualized clinical management for lupus patients.

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

Lupus nephritis (LN) remains a severe complication in systemic lupus erythematosus (SLE). Over the last decade, antiphospholipid antibodies have become a part of SLE classification criteria, and awareness of cardiovascular morbidity and its risk factors in SLE has increased. This study investigated the potential effect of these alterations on the presentation and severity of LN. This is an observational study of two subsequent SLE inception cohorts based on 1982 American College of Rheumatology (acr) classification criteria (82acr; n=87, enrolled 1978-95) and the updated version in 1997 (97acr: n=62, enrolled 1996-2006). Annual incidence rates (AIR), point prevalence, clinical and histological features, and outcome of LN (defined as proteinuria with urinary casts and/or haematuria) were compared between both cohorts. Between 1978 and 2006, the AIR for LN decreased from 0.7 to 0.45/100 000, while LN prevalence rose from 7 to 14/100 000. The relative risk reduction in the 97acr for early- and late-onset LN (> 3 months after SLE diagnosis) was 39% and 42%, respectively. Patients developing LN in the 97acr cohort (97LN+; n=11) had similar demographics, more often low avidity anti-dsDNA antibodies (Ab) and/or anti-cardiolipin Ab at SLE diagnosis, lower proteinuria and diastolic blood pressure, and similar histological findings to those in the 83acr cohort (82LN +; n=28). Following LN diagnosis, more 97LN + patients received pulse corticosteroids (55% vs. 7%), anticoagulants (46% vs. 4%) and antihypertensive drugs (46% vs. 11%). Three 82LN+ patients (11%) developed end-stage renal disease versus none in 97LN + during a 10-year follow-up. Early detection of low avidity anti-dsDNA and antiphospholipid antibodies, probably in combination with early use of protective cardiovascular measures from SLE diagnosis onwards may contribute to reduced incidence and improved renal survival in LN.

Regulatory polymorphisms in EGR2 are associated with susceptibility to systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is an autoimmune disease induced by the combinations of environmental and genetic factors. Recently, mice in which the early growth response 2 (EGR2) gene, a zinc-finger transcription factor, is conditionally knocked out in CD2(+) T cells have been shown to develop a lupus-like autoimmune disease. Here, we evaluated if polymorphisms in the EGR2 gene influence SLE susceptibility in humans. We first analyzed the effect of SNPs in the EGR2 region on EGR2 expression, and a significant positive correlation with expression was identified in an SNP located at the 5' flanking region of EGR2 (rs10761670, R=0.23, P=0.00072). We then performed a case-control association study using three sets of SLE cohorts by genotyping 14 tag SNPs in the EGR2 gene region. A peak of association with SLE susceptibility was observed for rs10761670 [Pooled: OR = 1.23 (95% CI 1.10-1.37), P=0.00023). This SNP was also associated with susceptibility to rheumatoid arthritis (RA) [OR = 1.15 (95% CI 1.05-1.26), P = 0.0019), suggesting that EGR2 is a common risk factor for SLE and RA. Among the SNPs in complete linkage disequilibrium with rs10761670 (r(2) = 1.0), two SNPs (rs1412554 and rs1509957) affected the binding of transcription factors and transcriptional activity in vitro, suggesting that they may be candidates of causal regulatory variants in this region. Therefore, EGR2 is a genetic risk factor for SLE, in which increased gene expression may contribute to SLE pathogenesis.

Management of cardiovascular complications in systemic lupus erythematosus

Cardiovascular disease (CVD) is a major cause of morbidity and mortality in patients with systemic lupus erythematosus (SLE). Patients with SLE have an excess risk compared with the general population; this is particularly pronounced in younger women with SLE who have an excess risk of over 50-fold compared with population controls. There is a higher prevalence of subclinical atherosclerosis in patients with SLE compared with controls, as demonstrated by a variety of imaging modalities discussed in this review. The causality of the excess risk of CVD and subclinical atherosclerosis is multifactorial in patients with SLE. While traditional risk factors play a role, after controlling for the traditional Framingham risk factors, the excess risk is still 7.5-fold greater than the general population. This review will also cover novel cardiovascular risk factors and some SLE-specific variables that contribute to CVD risk. This review discusses the risk factor modification and the evidence available for treatment of these risk factors in SLE. There have not yet been any published randomized, controlled trials in patients with SLE with respect to CVD risk factor modifications. Thus, the treatment and management recommendations are based largely on published guidelines for other populations at high risk for CVD.

Guilt by Association: The Challenge of Teasing Apart the Effect of Various Risk Factors for Coronary Heart Disease in Systemic Lupus Erythematosus

Since the original description over 3 decades ago of the association between atherosclerotic coronary heart disease (CHD) and systemic lupus erythematosus (SLE) by Urowitz, et al 1 many advances have been made in our understanding of the role of traditional, novel, and disease-related risk factors for clinical CHD in SLE2. Esdaile, et al have shown that traditional risk factors such as hypercholesterolemia and hypertension account only partly for the increased risk of CHD in SLE, indicating that disease- and treatment-related factors may also be important3. In the latest installment in the field, published in this issue of The Journal, Haque, et al seek to identify and quantify the role of various risk factors for clinical CHD in SLE, using a case-control design4. They show that patients with clinical CHD are more likely to be male, older, and hypertensive, to have a family history of CHD, to have more “damage” on the Systemic Lupus International Collaborating Clinics/American College of Rheumatology (SLICC/ACR) damage index, and to have been exposed to azathioprine prior to their CHD event. The “LASER” study highlights several methodological challenges in studies of cardiovascular risk factors in SLE. The first challenge relates to study design. While prospective collection of data on risk factors and CHD outcomes is the ideal model, many studies to date, including the LASER study, have used a retrospective chart review method. Not only does this introduce a possible source of bias, particularly in relation to the temporal association between exposure and outcome, it also means that the dataset may be incomplete for certain key variables. Here the choice and definition of risk factors (“independent variables”) for inclusion in the analysis are also limited to information that is routinely collected and documented in the course of clinical care. In the … Address correspondence to Dr. Nikpour. E-mail: mnikpour{at}medstv.unimelb.edu.au

Genetic variation at the IRF7/PHRF1 locus is associated with autoantibody profile and serum interferon‐α activity in lupus patients

Interferon-alpha (IFNalpha) is a heritable risk factor for systemic lupus erythematosus (SLE). Genetic variation near IRF7 is implicated in SLE susceptibility. SLE-associated autoantibodies can stimulate IFNalpha production through the Toll-like receptor/IRF7 pathway. This study was undertaken to determine whether variants of IRF7 act as risk factors for SLE by increasing IFNalpha production and whether autoantibodies are important to this phenomenon. We studied 492 patients with SLE (236 African American, 162 European American, and 94 Hispanic American subjects). Serum levels of IFNalpha were measured using a reporter cell assay, and single-nucleotide polymorphisms (SNPs) in the IRF7/PHRF1 locus were genotyped. In a joint analysis of European American and Hispanic American subjects, the rs702966 C allele was associated with the presence of anti-double-stranded DNA (anti-dsDNA) antibodies (odds ratio [OR] 1.83, P = 0.0069). The rs702966 CC genotype was only associated with higher serum levels of IFNalpha in European American and Hispanic American patients with anti-dsDNA antibodies (joint analysis P = 4.1 x 10(-5) in anti-dsDNA-positive patients and P = 0.99 in anti-dsDNA-negative patients). In African American subjects, anti-Sm antibodies were associated with the rs4963128 SNP near IRF7 (OR 1.95, P = 0.0017). The rs4963128 CT and TT genotypes were associated with higher serum levels of IFNalpha only in African American patients with anti-Sm antibodies (P = 0.0012). In African American patients lacking anti-Sm antibodies, an effect of anti-dsDNA-rs702966 C allele interaction on serum levels of IFNalpha was observed, similar to the other patient groups (overall joint analysis P = 1.0 x 10(-6)). In European American and Hispanic American patients, the IRF5 SLE risk haplotype showed an additive effect with the rs702966 C allele on IFNalpha level in anti-dsDNA-positive patients. Our findings indicate that IRF7/PHRF1 variants in combination with SLE-associated autoantibodies result in higher serum levels of IFNalpha, providing a biologic relevance for this locus at the protein level in human SLE in vivo.

The association of a nonsynonymous single‐nucleotide polymorphism in TNFAIP3 with systemic lupus erythematosus and rheumatoid arthritis in the Japanese population

Genome-wide association (GWA) studies in systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA) in Caucasian populations have independently identified risk variants in and near the tumor necrosis factor alpha (TNFalpha)-induced protein 3 gene (TNFAIP3), which is crucial for the regulation of TNF-mediated signaling and Toll-like receptor signaling. The aim of this study was to assess the role of TNFAIP3 in the development of SLE and RA in Japanese subjects. We selected 2 single-nucleotide polymorphisms (SNPs) from previous GWA studies. Rs2230926 is a nonsynonymous SNP in TNFAIP3 and is associated with SLE, while rs10499194 is an intergenic SNP associated with RA. We then performed 2 independent sets of SLE case-control comparisons (717 patients and 1,362 control subjects) and 3 sets of RA case-control comparisons (3,446 patients and 2,344 control subjects) using Japanese subjects. We genotyped SNPs using TaqMan assays. We observed a significant association between rs2230926 and an increased risk of SLE and RA in the Japanese population (for SLE, odds ratio [OR] 1.92, 95% confidence interval [95% CI] 1.53-2.41, P = 1.9 x 10(-8); for RA, OR 1.35, 95% CI 1.18-1.56, P = 2.6 x 10(-5)). The intergenic SNP rs10499194 was also associated with SLE and RA, while the risk allele for RA in Caucasians was protective against the diseases in our population. We demonstrated a significant association between the nonsynonymous variant in TNFAIP3 and the risk for SLE and RA in the Japanese population. TNFAIP3, similar to STAT4 and IRF5, may be a common genetic risk factor for SLE and RA that is shared between the Caucasian and Japanese populations.

C1q inhibits immune complex–induced interferon‐α production in plasmacytoid dendritic cells: A novel link between C1q deficiency and systemic lupus erythematosus pathogenesis

C1q deficiency is the strongest risk factor known for the development of systemic lupus erythematosus (SLE), since almost all humans with a genetic deficiency of C1q develop this disease. Low C1q serum concentration is also a typical finding in SLE during flares, emphasizing the involvement of C1q in SLE pathogenesis. Recent studies have revealed that C1q has a regulatory effect on Toll-like receptor-induced cytokine production. Therefore, we undertook this study to investigate whether C1q could regulate production of interferon-alpha (IFNalpha). Peripheral blood mononuclear cells (PBMCs) and plasmacytoid dendritic cells (PDCs) were stimulated with 3 known interferogenic stimuli and cultured with physiologic concentrations of C1q. IFNalpha production was determined by an immunoassay. C1q significantly inhibited PBMC IFNalpha production induced by RNA-containing immune complexes (ICs), herpes simplex virus (HSV), and CpG DNA. C1q also inhibited PDC IFNalpha production induced by ICs and CpG DNA but increased PDC IFNalpha production induced by HSV. The regulatory role of C1q was not specific for IFNalpha but was also seen for interleukin-6 (IL-6), IL-8, and tumor necrosis factor alpha. We demonstrated binding of C1q to PDCs both by surface plasmon resonance interaction analysis and by flow cytometry, and we also demonstrated intracellular detection of 2 C1q binding proteins. Our findings contribute to the understanding of why C1q deficiency is such a strong risk factor for SLE and suggest an explanation for the up-regulation of the type I IFN system seen in SLE patients.

Rheumatoid arthritis does not share most of the newly identified systemic lupus erythematosus genetic factors

Rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE) share some genetic factors such as HLA, PTPN22, STAT4, and 6q23. The aim of this study was to determine whether 9 other SLE genetic factors are also implicated in RA susceptibility. A characteristic single-nucleotide polymorphism (SNP) in each of 9 genetic factors, ITGAM (rs1143679), C8orf13-BLK (rs13277113), TYK2 (rs2304256), 1q25.1 (rs10798269), PXK (rs6445975), KIAA1542 (rs4963128), MECP2 (rs17435), BANK1 (rs17266594), and LY9 (rs509749), was studied in 1,635 patients with RA and 1,906 control subjects from Spain. The rs7574865 SNP in STAT4 was also included. Analyses were conducted globally and after stratification by sex and clinical features (anti-cyclic citrullinated peptide and rheumatoid factor, shared epitope, rheumatoid nodules, radiographic changes, sicca syndrome, and pneumonitis). No association was observed between RA and any of the 9 newly identified SLE genetic factors. A meta-analysis using previous data was consistent with these results. In addition, there were no significant differences between individuals with and those without each of the clinical features analyzed, except the frequency of the minor allele in the C8orf13-BLK locus that was decreased in patients with sicca syndrome (14.6% versus 22.4% in controls; P = 0.003). None of the 9 recently identified SLE risk factors showed association with RA. Therefore, common genetic factors affecting the pathogenesis of these 2 disorders seem to be limited, revealing that the genetic component contributes to the different expression of these diseases.