Systemic lupus erythematosus (SLE) is a highly heterogeneous disorder, characterized by differences in autoantibody profile, serum cytokines, and clinical manifestations. SLE-associated autoantibodies and high serum interferon alpha (IFN-α) are important heritable phenotypes in SLE which are correlated with each other, and play a role in disease pathogenesis. These two heritable risk factors are shared between ancestral backgrounds. The aim of the study was to detect genetic factors associated with autoantibody profiles and serum IFN-α in SLE.
We undertook a case-case genome-wide association study of SLE patients stratified by ancestry and extremes of phenotype in serology and serum IFN-α. Single nucleotide polymorphisms (SNPs) in seven loci were selected for follow-up in a large independent cohort of 538 SLE patients and 522 controls using a multi-step screening approach based on novel metrics and expert database review. The seven loci were: leucine-rich repeat containing 20 (LRRC20); protein phosphatase 1 H (PPM1H); lysophosphatidic acid receptor 1 (LPAR1); ankyrin repeat and sterile alpha motif domain 1A (ANKS1A); protein tyrosine phosphatase, receptor type M (PTPRM); ephrin A5 (EFNA5); and V-set and immunoglobulin domain containing 2 (VSIG2).
SNPs in the LRRC20, PPM1H, LPAR1, ANKS1A, and VSIG2 loci each demonstrated strong association with a particular serologic profile (all odds ratios > 2.2 and P < 3.5 × 10-4). Each of these serologic profiles was associated with increased serum IFN-α. SNPs in both PTPRM and LRRC20 were associated with increased serum IFN-α independent of serologic profile (P = 2.2 × 10-6 and P = 2.6 × 10-3 respectively). None of the SNPs were strongly associated with SLE in case-control analysis, suggesting that the major impact of these variants will be upon subphenotypes in SLE.
This study demonstrates the power of using serologic and cytokine subphenotypes to elucidate genetic factors involved in complex autoimmune disease. The distinct associations observed emphasize the heterogeneity of molecular pathogenesis in SLE, and the need for stratification by subphenotypes in genetic studies. We hypothesize that these genetic variants play a role in disease manifestations and severity in SLE.
The type I interferon (IFN) pathway is activated in many patients with systemic lupus erythematosus (SLE), and high serum levels of IFN are associated with anti-SSA/Ro autoantibodies. To investigate the clinical features associated with type I IFN production in vivo, we compared serum IFN activity in individuals with anti-SSA/Ro antibodies who were asymptomatic with that in individuals with clinical manifestations of SLE or Sjögren's syndrome (SS).
Antibody-positive sera from 84 mothers of children with manifestations of neonatal lupus were studied for type I IFN activity, using a functional reporter cell assay. Maternal health status was characterized as asymptomatic, SS, SLE, pauci-SLE, or pauci-SS, based on a screening questionnaire, telephone interview, and review of medical records. The prefix “pauci-” indicates symptoms insufficient for a formal classification of the disease.
Only 4% of asymptomatic mothers had high serum type I IFN activity, compared with 73% with pauci-SLE (P = 5.7 × 10−5), 35% with SLE (P = 0.011), and 32% of patients with SS (P = 0.032). One of the 4 patients with pauci-SS had high levels of IFN. The majority of patients for whom longitudinal data were available had stable type I IFN activity over time, and changes in IFN activity were not clearly accompanied by changes in the clinical diagnosis.
Patients with SLE, patients with pauci-SLE, and patients with SS are more likely to have high serum IFN activity than asymptomatic individuals with SSA/Ro autoantibodies, suggesting that these autoantibodies are insufficient for activation of the type I IFN pathway, and that disease-specific factors are important for type I IFN generation in vivo.
Examine the relationship between circulating B lymphocyte stimulator (BLyS) levels and humoral responses to influenza vaccination in systemic lupus erythematosus (SLE) patients, as well as the effect of vaccination on BLyS levels. Clinical and serologic features of SLE that are associated with elevated BLyS levels will also be investigated.
Clinical history, disease activity measurements and blood specimens were collected from sixty SLE patients at baseline and after influenza vaccination. Sera were tested for BLyS levels, lupus-associated autoantibodies, serum IFN-α activity, 25-hydroxyvitamin D, and humoral responses to influenza vaccination.
Thirty percent of SLE patients had elevated BLyS levels, with African American patients having higher BLyS levels than European American patients (p=0.006). Baseline BLyS levels in patients were not correlated with humoral responses to influenza vaccination (p=0.863), and BLyS levels increased post-vaccination only in the subset of patients in the lowest quartile of BLyS levels (p=0.0003). Elevated BLyS levels were associated with increased disease activity as measured by SLEDAI, PGA, and SLAM in European Americans (p=0.035, p=0.016, p=0.018, respectively), but not in African Americans. Elevated BLyS levels were also associated with anti-nRNP (p=0.0003) and decreased 25(OH)D (p=0.018). Serum IFN-α activity was a significant predictor of elevated BLyS in a multivariate analysis (p=0.002).
African American SLE patients have higher BLyS levels regardless of disease activity. Humoral response to influenza vaccination is not correlated with baseline BLyS levels in SLE patients and only those patients with low baseline BLyS levels demonstrate an increased BLyS response after vaccination.
Systemic lupus erythematosus (SLE); Cytokines
Purpose. This study evaluates high-throughput autoantibody screening and determines associated systemic lupus erythematosus (SLE) clinical features in a large lupus cohort. Methods. Clinical and demographic information, along with serum samples, were obtained from each SLE study participant after appropriate informed consent. Serum samples were screened for 10 distinct SLE autoantibody specificities and examined for association with SLE ACR criteria and subcriteria using conditional logistic regression analysis. Results. In European-American SLE patients, autoantibodies against 52 kD Ro and RNP 68 are independently enriched in patients with lymphopenia, anti-La, and anti-ribosomal P are increased in patients with malar rash, and anti-dsDNA and anti-Sm are enriched in patients with proteinuria. In African-American SLE patients, cellular casts associate with autoantibodies against dsDNA, Sm, and Sm/nRNP. Conclusion. Using a high-throughput, bead-based method of autoantibody detection, anti-dsDNA is significantly enriched in patienets with SLE ACR renal criteria as has been previously described. However, lymphopenia is associated with several distinct autoantibody specificities. These findings offer meaningful information to allow clinicians and clinical investigators to understand which autoantibodies correlate with select SLE clinical manifestations across common racial groups using this novel methodology which is expanding in clinical use.
Background: Systemic lupus erythematosus (SLE) is an autoimmune disease affecting multiple organ systems triggered by the production of autoantibodies. Previous clinical studies in humans and murine models suggest that type I interferons (IFNs) are important for the initiation and potentiation of SLE activity.
Methods: 65 consecutive patients with SLE were identified from the University of California, San Francisco Lupus Clinic with moderate-severe disease activity. 94 serological samples were collected. Type I IFN levels and the ability of plasma to induce expression of several surface markers of dendritic cell maturation were measured.
Results: Type I IFN levels correlated with the presence of cutaneous manifestations, and there was a trend towards correlation with renal disease. No correlation was found between type I IFN levels and neurological disease. Type I IFN levels correlated positively with the SLEDAI score and anti-dsDNA levels and inversely with C3 levels. Interestingly, type I IFN levels were highest in African American patients. SLE plasma also induced the expression of MHC class I, CD38, and CD123 on monocytes, and was blocked by the addition of a monoclonal antibody to IFNAR1.
Conclusions: The pathogenic role of type I IFN is suggested by the induction of cell surface markers for dendritic cell maturation. The potential therapeutic utility of antibodies directed to either type I IFN or IFNAR1/IFNAR2 may be of interest in further studies.
To determine the features associated with acute onset systemic lupus erythaematosus (SLE).
A total of 631 SLE patients from LUMINA (for “lupus in minority populations: nature vs nurture”), a multiethnic (Hispanics, African–Americans and Caucasians) cohort, were studied. Acute disease onset was defined as the accrual of ≥4 American College of Rheumatology (ACR) criteria for the classification of SLE in ≤4 weeks. Socioeconomic demographic features, clinical manifestations, disease activity, damage accrual, mortally, autoantibodies. HLA class II and FCGR alleles, behavioural/psychological variables were compared between patients with acute and insidious disease onset by univariable (χ2 and Student t test) and multivariable (stepwise logistic regression) analyses.
A total of 94 (15%) patients had acute disease onset. In the multivariable analysis, patients with acute onset lupus had more renal involvement (odds ratio (OR) = 1.845, 95% CI 1.076–3.162; p = 0.026) and higher disease activity (OR = 1.057, 95% CI 1.005–1.112; p = 0.030). By contrast, age (OR = 0.976, 95% CI 0.956–0.997; p = 0.025), education (OR = 0.901, 95% CI 0.827–0.983, p = 0.019), health insurance (OR = 0.423, 95% CI 0.249–0.718; p = 0.001) and skin involvement (OR = 0.346, 95% CI 0.142–0.843; p = 0.019) were negatively associated with acute onset lupus. No differences were found regarding the serological, genetic and behavioural/psychological features; this was also the case for damage accrual and mortality.
Patients with acute onset lupus seem to be younger, have a lower socio-economic status and display more severe disease in terms of clinical manifestations and disease activity. However, intermediate (damage) and long-term (mortality) outcomes appear not to be influenced by the type of disease onset in SLE.
Systemic lupus erythematosus (SLE) is a highly heterogeneous autoimmune disorder characterized by differences in autoantibody profiles, serum cytokines, and clinical manifestations. We have previously conducted a case-case genome-wide association study (GWAS) of SLE patients to detect associations with autoantibody profile and serum interferon alpha (IFN-α). In this study, we used public gene expression data sets to rationally select additional single nucleotide polymorphisms (SNPs) for validation. The top 200 GWAS SNPs were searched in a database which compares genome-wide expression data to genome-wide SNP genotype data in HapMap cell lines. SNPs were chosen for validation if they were associated with differential expression of 15 or more genes at a significance of P < 9 × 10−5. This resulted in 11 SNPs which were genotyped in 453 SLE patients and 418 matched controls. Three SNPs were associated with SLE-associated autoantibodies, and one of these SNPs was also associated with serum IFN-α (P < 4.5 × 10−3 for all). One additional SNP was associated exclusively with serum IFN-α. Case-control analysis was insensitive to these molecular subphenotype associations. This study illustrates the use of gene expression data to rationally select candidate loci in autoimmune disease, and the utility of stratification by molecular phenotypes in the discovery of additional genetic associations in SLE.
Systemic lupus erythematosus (SLE) is a clinically and serologically complex disease that demonstrates clinical, epidemiological and genetic differences among racial and ethnic groups. Some autoantibodies are useful for diagnosis of the illness. Others are clinically important because of associations with a particular manifestation of SLE. Antibodies to RNA helicase A (anti-RHA) comprise a newly described class of SLE autoantibodies. These antibodies have so far been found only in SLE patients and differ substantially in prevalence and nature between Mexican and white American SLE patients. Study of anti-RHA may provide insights into the origin of population differences in SLE.
Growing evidence over the last few years suggests a central role of type I IFN pathway in the pathogenesis of systemic autoimmune disorders. Data from clinical and genetic studies in patients with systemic lupus erythematosus (SLE) and lupus-prone mouse models, indicates that the type I interferon system may play a pivotal role in the pathogenesis of several lupus and associated clinical features, such as nephritis, neuropsychiatric and cutaneous lupus, premature atherosclerosis as well as lupus-specific autoantibodies particularly against ribonucleoproteins. In the current paper, our aim is to summarize the latest findings supporting the association of type I IFN pathway with specific clinical manifestations in the setting of SLE providing insights on the potential use of type I IFN as a therapeutic target.
The PIK3C3 locus was implicated in case-case genome-wide association study of systemic lupus erythematosus (SLE) which we had performed to detect genes associated with autoantibodies and serum interferon-alpha (IFN-α). Herein, we examine a PIK3C3 promoter variant (rs3813065/-442 C/T) in an independent multiancestral cohort of 478 SLE cases and 522 controls. rs3813065 C was strongly associated with the simultaneous presence of both anti-Ro and anti-Sm antibodies in African-American patients [OR = 2.24 (1.34–3.73), P = 2.0 × 10−3]. This autoantibody profile was associated with higher serum IFN-α (P = 7.6 × 10−6). In the HapMap Yoruba population, rs3813065 was associated with differential expression of ERAP2 (P = 2.0 × 10−5), which encodes an enzyme involved in MHC class I peptide processing. Thus, rs3813065 C is associated with a particular autoantibody profile and altered expression of an MHC peptide processing enzyme, suggesting that this variant modulates serologic autoimmunity in African-American SLE patients.
Systemic lupus erythematosus (SLE) is a systemic autoimmune disease characterized by increased type I interferons (IFNs) and multiorgan inflammation frequently targeting the skin. IFN-kappa is a type I IFN expressed in skin. A pooled genome-wide scan implicated the IFNK locus in SLE susceptibility. We studied IFNK single nucleotide polymorphisms (SNPs) in 3982 SLE cases and 4275 controls, composed of European (EA), African-American (AA), and Asian ancestry. rs12553951C was associated with SLE in EA males (odds ratio = 1.93, P = 2.5 × 10−4), but not females. Suggestive associations with skin phenotypes in EA and AA females were found, and these were also sex-specific. IFNK SNPs were associated with increased serum type I IFN in EA and AA SLE patients. Our data suggest a sex-dependent association between IFNK SNPs and SLE and skin phenotypes. The serum IFN association suggests that IFNK variants could influence type I IFN producing plasmacytoid dendritic cells in affected skin.
Systemic Lupus Erythematosus (SLE) shows a spectrum of clinical manifestations that complicate its diagnosis, treatment and research. This variability is likely related with environmental exposures and genetic factors among which known SLE susceptibility loci are prime candidates. The first published analyses seem to indicate that this is the case for some of them, but results are still inconclusive and we aimed to further explore this question.
European SLE patients, 1444, recruited at 17 centres from 10 countries were analyzed. Genotypes for 26 SLE associated SNPs were compared between patients with and without each of 11 clinical features: ten of the American College of Rheumatology (ACR) classification criteria (except ANAs) and age of disease onset. These analyses were adjusted for centre of recruitment, top ancestry informative markers, gender and time of follow-up. Overlap of samples with previous studies was excluded for assessing replication.
There were three new associations: the SNPs in XKR6 and in FAM167A-BLK were associated with lupus nephritis (OR = 0.76 and 1.30, Pcorr = 0.007 and 0.03, respectively) and the SNP of MECP2, which is in chromosome X, with earlier age of disease onset in men. The previously reported association of STAT4 with early age of disease onset was replicated. Some other results were suggestive of the presence of additional associations. Together, the association signals provided support to some previous findings and to the characterization of lupus nephritis, autoantibodies and age of disease onset as the clinical features more associated with SLE loci.
Some of the SLE loci shape the disease phenotype in addition to increase susceptibility to SLE. This influence is more prominent for some clinical features than for others. However, results are only partially consistent between studies and subphenotype specific GWAS are needed to unravel their genetic component.
Systemic lupus erythematosus (SLE) is an autoimmune disease characterized by multiple genetic risk factors, high levels of interferon alpha (IFN-α), and the production of autoantibodies against components of the cell nucleus. Interferon regulatory factor 5 (IRF5) is a transcription factor which induces the transcription of IFN-α and other cytokines, and genetic variants of IRF5 have been strongly linked to SLE pathogenesis. IRF5 functions downstream of Toll-like receptors and other microbial pattern-recognition receptors, and immune complexes made up of SLE-associated autoantibodies seem to function as a chronic endogenous stimulus to this pathway. In this paper, we discuss the physiologic role of IRF5 in immune defense and the ways in which IRF5 variants may contribute to the pathogenesis of human SLE. Recent data regarding the role of IRF5 in both serologic autoimmunity and the overproduction of IFN-α in human SLE are summarized. These data support a model in which SLE-risk variants of IRF5 participate in a “feed-forward” mechanism, predisposing to SLE-associated autoantibody formation, and subsequently facilitating IFN-α production downstream of Toll-like receptors stimulated by immune complexes composed of these autoantibodies.
UBE2L3 is associated with susceptibility to systemic lupus erythematosus (SLE) and rheumatoid arthritis in European ancestry populations, and this locus has not been investigated fully in non-European populations. We studied the UBE2L3 risk allele for association with SLE, interferon-α (IFN-α), and autoantibodies in a predominantly African American SLE cohort.
We studied 395 patients with SLE and 344 controls. The UBE2L3 rs5754217 polymorphism was genotyped using Taqman primer-probe sets, and IFN-α was measured using a reporter cell assay.
The UBE2L3 rs5754217 T allele was strongly enriched in African American patients with anti-La antibodies as compared to controls, and a recessive model was the best fit for this association (OR 2.55, p = 0.0061). Serum IFN-α also demonstrated a recessive association with the rs5754217 genotype in African American patients, and the TT/anti-La-positive patients formed a significantly high IFN-α subgroup (p = 0.0040). Similar nonstatistically significant patterns of association were observed in the European American patients with SLE. Case-control analysis did not show large allele frequency differences, supporting the idea that this allele is most strongly associated with anti-La-positive patients.
This pattern of recessive influence within a subgroup of patients may explain why this allele does not produce a strong signal in standard case-control studies, and subphenotypes should be included in future studies of UBE2L3. The interaction we observed between UBE2L3 genotype and autoantibodies upon serum IFN-α suggests a biological role for this locus in patients with SLE in vivo.
SYSTEMIC LUPUS ERYTHEMATOSUS; GENETICS INTERFERON-α; AUTOANTIBODIES; UBE2L3 GENOTYPE
Systemic lupus erythematosus (SLE) is an autoimmune disease with diverse clinical manifestations characterized by the development of pathogenic autoantibodies manifesting in inflammation of target organs such as the kidneys, skin and joints. Genome-wide association studies have identified genetic variants in the UBE2L3 region that are associated with SLE in subjects of European and Asian ancestry. UBE2L3 encodes an ubiquitin-conjugating enzyme, UBCH7, involved in cell proliferation and immune function. In this study, we sought to further characterize the genetic association in the region of UBE2L3 and use molecular methods to determine the functional effect of the risk haplotype. We identified significant associations between variants in the region of UBE2L3 and SLE in individuals of European and Asian ancestry that exceeded a Bonferroni corrected threshold (P < 1 × 10−4). A single risk haplotype was observed in all associated populations. Individuals harboring the risk haplotype display a significant increase in both UBE2L3 mRNA expression (P = 0.0004) and UBCH7 protein expression (P = 0.0068). The results suggest that variants carried on the SLE associated UBE2L3 risk haplotype influence autoimmunity by modulating UBCH7 expression.
Systemic Lupus Erythematosus; UBE2L3; Multi Ethnic Association Study; UBCH7 Expression
Earlier studies from several laboratories showed that interferon-alpha (IFN-alpha) is present in the sera of a large percentage of patients with systemic lupus erythematosus (SLE). We now report the detection of IFN-alpha by indirect immunofluorescence in renal sections of three patients with SLE but not in six control kidneys. The immunofluorescence reaction was mediated by three hyperimmune antisera to IFN-alpha raised in three different species, but not by any preimmune serum. The reaction was specifically blocked by absorption of the anti-IFN-alpha sera with purified IFN-alpha made by recombinant DNA techniques or with IFN-alpha isolated from the serum of an SLE patient, but not by bovine serum albumin or human immunoglobulin G. In contrast, antisera to IFN-beta or IFN-gamma did not mediate immunofluorescence. The pattern of IFN-alpha deposition resembled that seen with anti-human immunoglobulin G, suggesting association with immune complexes. Immune complexes were then preparatively eluted from the homogenate of an SLE kidney by treatment with buffer at pH 2.8. Biologically active IFN was found in this eluate and was demonstrated to be IFN-alpha by specific neutralization with IFN antisera. These results extend the specific association of IFN-alpha with SLE.
Systemic lupus erythematosus (SLE) is diagnosed by a spectrum of clinical manifestations and autoantibodies associated with abnormal expression of Type I interferon (IFN-I) stimulated genes (ISGs). The role of IFN-I in the pathogenesis of SLE remains uncertain, partly due to the lack of suitable animal models. The objective of this study was to examine the role of IFN-I signaling in the pathogenesis of murine lupus induced by 2, 6, 10, 14 tetramethylpentadecane (TMPD).
129Sv IFN-I receptor deficient (IFNAR−/−) and control 129Sv mice were treated i.p. with TMPD. The expression of ISGs was measured by real-time PCR. Autoantibody production was evaluated by immunofluorescence and ELISA. Proteinuria and renal glomerular cellularity were measured and renal immune complexes were examined by immunofluorescence.
Increased ISG expression was seen in peripheral blood of TMPD-treated wild type but not IFNAR−/− mice. TMPD did not induce lupus-specific autoantibodies (anti-nRNP/Sm, -dsDNA) in IFNAR−/− mice, whereas 129Sv controls developed these specificities. Although glomerular immune complexes were present in IFNAR−/− mice, proteinuria and glomerular hypercellularity did not develop, unlike TMPD-treated controls. Thus, consistent with the association of increased ISG expression with lupus-specific autoantibodies, and nephritis in humans, these clinical and serological manifestations were strongly dependent on IFNAR signaling in TMPD-treated mice.
Signaling via the IFNAR is central to the pathogenesis of autoantibodies and glomerulonephritis in TMPD-lupus, consistent with a similar role in human SLE. TMPD-lupus is the first animal model shown to recapitulate the interferon signature in peripheral blood.
Patients with systemic lupus erythematosus (SLE) often suffer from depression and fatigue in addition to the physical manifestations of the autoimmune disease. Elevated production of type-I interferons (IFN-I) has been found in lupus patients and IFN-I can precipitate a variety of neuropsychiatric side effects. This study was conducted to evaluate the relationship between dysregulated IFN-I production and the presence of depression or fatigue in lupus patients. Through cross-sectional and longitudinal analysis we found no significant correlation between abnormal IFN-I levels (as measured by peripheral blood expression of IFN-I-stimulated genes) and neuropsychiatric manifestations. Elevation of endogenous serum IFN-I levels is unlikely to account for the depression and fatigue associated with SLE.
Systemic lupus erythematosus; depression; fatigue; type I interferon
Interferon α (IFN-α) levels are elevated in many patients with systemic lupus erythematosus (SLE); however it is not known whether high serum IFN-α activity is a cause or a result of the disease. We studied 266 SLE patients and 405 of their healthy relatives, and frequently found high serum IFN-α activity in both patients and healthy relatives as compared to healthy unrelated individuals. High IFN-α activity was clustered in specific families in both SLE patients and their healthy first-degree relatives, suggesting a heritable trait. Heritability was also supported by quantitative familial correlation of IFN-α activity, concordance in affected sib pairs and frequent transmission of the high IFN-α activity trait from parents to offspring. Autoantibodies to RNA-binding proteins and double-stranded DNA were associated with high IFN-α activity in SLE patients; however these autoantibodies were very uncommon in healthy family members and did not explain the observed familial correlations. The frequency of high IFN-α activity was similar across all studied ethnic backgrounds. These data suggest that high serum IFN-α activity is a complex heritable trait, which plays a primary role in SLE pathogenesis.
interferon α; systemic lupus erythematosus; genetics; epidemiology; autoantibodies
Systemic lupus erythematosus (SLE) is a severe multi-system autoimmune disease which results from both genetic predisposition and environmental factors. Many lines of investigation support interferon alpha (IFN-α) as a causal agent in human lupus, and high levels of serum IFN-α are a heritable risk factor for SLE. Interferon regulatory factors (IRFs) are a family of transcription factors involved in host defense, which can induce transcription of IFN-α and other immune response genes following activation. In SLE, circulating immune complexes which contain nucleic acid are prevalent. These complexes are recognized by endosomal Toll-like receptors, resulting in activation of downstream IRF proteins. Genetic variants in the IRF5 and IRF7 genes have been associated with SLE susceptibility, and these same variants are associated with increased serum IFN-α in SLE patients. The increase in serum IFN-α related to IRF5 and 7 genotypes is observed only in patients with particular antibody specificities. This suggests that chronic stimulation of the endosomal Toll-like receptors by autoantibody immune complexes is required for IRF SLE-risk variants to cause elevation of circulating IFN-α and subsequent risk of SLE. Recently, genetic variation in the IRF8 gene has been associated with SLE and multiple sclerosis, and studies support an impact of IRF8 genotype on the IFN-α pathway. In summary, the SLE-associated polymorphisms in the IRF family of proteins appear to be gain-of-function variants, and understanding the impact of these variants upon the IFN-α pathway in vivo may guide therapeutic strategies directed at the Toll-like receptor/IRF/IFN-α pathway in SLE.
Interferon Alpha; Genetics; Systemic Lupus Erythematosus; Interferon Regulatory Factor; Autoantibodies; Autoimmunity
To determine whether genetic substructure in European-derived populations is associated with specific manifestations of systemic lupus erythematosus (SLE), including mucocutaneous phenotypes, autoantibody production, and renal disease.
SLE patients of European descent (n=1754) from 8 case collections were genotyped for over 1,400 ancestry informative markers that define a north/south gradient of European substructure. Based on these genetic markers, we used the STRUCTURE program to characterize each SLE patient in terms of percent northern (vs. southern) European ancestry. Non-parametric methods, including tests of trend, were used to identify associations between northern European ancestry and specific SLE manifestations.
In multivariate analyses, increasing levels of northern European ancestry were significantly associated with photosensitivity (ptrend=0.0021, OR for highest quartile of northern European ancestry compared to lowest quartile 1.64, 95% CI 1.13–2.35) and discoid rash (ptrend=0.014, ORhigh-low 1.93, 95% CI 0.98–3.83). In contrast, northern European ancestry was protective for anticardiolipin (ptrend=1.6 × 10−4, ORhigh-low 0.46, 95% CI 0.30–0.69) and anti-dsDNA (ptrend=0.017, ORhigh-low 0.67, 95% CI 0.46–0.96) autoantibody production.
This study demonstrates that specific SLE manifestations vary according to northern vs. southern European ancestry. Thus, genetic ancestry may contribute to the clinical heterogeneity and variation in disease outcomes among SLE patients of European descent. Moreover, these results suggest that genetic studies of SLE subphenotypes will need to carefully address issues of population substructure due to genetic ancestry.
The objective of this study is to examine the clinical features and outcomes of patients with systemic lupus erythematosus (SLE) whose disease began in adolescence [juvenile-onset SLE (jSLE)] compared with adult-onset patients [adult-onset SLE (aSLE)] from a large multiethnic cohort. Systemic lupus erythematosus patients of African-American, Caucasian, or Hispanic ethnicity and ≥1 year follow-up were studied in two groups: jSLE (diagnosed at ≤18 years); aSLE (diagnosed at 19–50 years; matched for gender and disease duration at enrolment). Sociodemographic data, SLE manifestations, disease activity, damage accrual, SLE-related hospitalizations or emergency room visits, drug utilization, mortality and psychosocial characteristics and quality of life were compared. Data were analysed by univariable and multivariable analyses. Seventy-nine patients were studied (31 jSLE, 48 aSLE); 90% were women. Mean (SD) total disease duration was 6.8 (2.7) years in jSLE and 5.6 (3.3) years in aSLE (p = 0.077). Mean age at cohort entry was 18.4 (1.8) and 33.9 (9.2) years in jSLE and aSLE respectively. By univariable analysis, jSLE patients were more commonly of African-American descent, were more likely to have renal and neurological involvements, and to accrue renal damage; jSLE patients had lower levels of helplessness and scored higher in the physical component measure of the SF-36 than aSLE patients. Renal involvement [OR = 1.549, 95% CI (1.397–15.856)] and neurological involvement [OR = 1.642, 95% CI (1.689–15.786)] were independently associated with jSLE by multivariable analysis. There was a larger proportion of African-Americans within the jSLE group. After adjusting for ethnicity and follow-up time, jSLE patients experienced more renal and neurological manifestations, with more renal damage. There was a two-fold higher mortality rate in the jSLE group.
juvenile-onset SLE; outcome
Increased IFN-α signaling is a heritable risk factor for systemic lupus erythematosus (SLE). IFN induced with helicase C domain 1 (IFIH1) is a cytoplasmic dsRNA sensor that activates IFN-α pathway signaling. We studied the impact of the autoimmune-disease–associated IFIH1 rs1990760 (A946T) single nucleotide polymorphism upon IFN-α signaling in SLE patients in vivo. We studied 563 SLE patients (278 African-American, 179 European-American, and 106 Hispanic-American). Logistic regression models were used to detect genetic associations with autoantibody traits, and multiple linear regression was used to analyze IFN-α–induced gene expression in PBMCs in the context of serum IFN-α in the same blood sample. We found that the rs1990760 T allele was associated with anti-dsDNA Abs across all of the studied ancestral backgrounds (meta-analysis odds ratio = 1.34, p = 0.026). This allele also was associated with lower serum IFN-α levels in subjects who had anti-dsDNA Abs (p = 0.0026). When we studied simultaneous serum and PBMC samples from SLE patients, we found that the IFIH1 rs1990760 T allele was associated with increased IFN-induced gene expression in PBMCs in response to a given amount of serum IFN-α in anti-dsDNA–positive patients. This effect was independent of the STAT4 genotype, which modulates sensitivity to IFN-α in a similar way. Thus, the IFIH1 rs1990760 Tallele was associated with dsDNA Abs, and in patients with anti-dsDNA Abs this risk allele increased sensitivity to IFN-α signaling. These studies suggest a role for the IFIH1 risk allele in SLE in vivo.
High serum interferon α (IFNα) activity is a heritable risk factor for systemic lupus erythematosus (SLE). Auto-antibodies found in SLE form immune complexes which can stimulate IFNα production by activating endosomal Toll-like receptors and interferon regulatory factors (IRFs), including IRF5. Genetic variation in IRF5 is associated with SLE susceptibility; however, it is unclear how IRF5 functional genetic elements contribute to human disease.
1034 patients with SLE and 989 controls of European ancestry, 555 patients with SLE and 679 controls of African–American ancestry, and 73 patients with SLE of South African ancestry were genotyped at IRF5 polymorphisms, which define major haplotypes. Serum IFNα activity was measured using a functional assay.
In European ancestry subjects, anti-double-stranded DNA (dsDNA) and anti-Ro antibodies were each associated with different haplotypes characterised by a different combination of functional genetic elements (OR > 2.56, p >003C; 1.9×10−14 for both). These IRF5 haplotype-auto-antibody associations strongly predicted higher serum IFNα in patients with SLE and explained > 70% of the genetic risk of SLE due to IRF5. In African–American patients with SLE a similar relationship between serology and IFNα was observed, although the previously described European ancestry-risk haplotype was present at admixture proportions in African–American subjects and absent in African patients with SLE.
The authors define a novel risk haplotype of IRF5 that is associated with anti-dsDNA antibodies and show that risk of SLE due to IRF5 genotype is largely dependent upon particular auto-antibodies. This suggests that auto-antibodies are directly pathogenic in human SLE, resulting in increased IFNα in cooperation with particular combinations of IRF5 functional genetic elements.
SLE is a systemic autoimmune disorder affecting multiple organ systems including the skin, musculoskeletal, renal and haematopoietic systems. Humoral autoimmunity is a hallmark of SLE, and patients frequently have circulating auto-antibodies directed against dsDNA, as well as RNA binding proteins (RBP). Anti-RBP autoantibodies include antibodies which recognize Ro, La, Smith (anti-Sm), and ribonucleoprotein (anti-nRNP), collectively referred to as anti-retinol-binding protein). Anti-retinol-binding protein and anti-dsDNA auto-antibodies are rare in the healthy population.1 These auto-antibodies can be present in sera for years preceding the onset of clinical SLE illness2 and are likely pathogenic in SLE.34
OBJECTIVES—To determine the frequency and type of cardiac manifestations in children with systemic lupus erythematosus (SLE) and investigate whether cardiac involvement of SLE in children was associated with any autoantibody pattern.
METHODS—Retrospective analysis of the medical records of all children with SLE (31 patients) seen between January 1984 and January 1994 by the paediatric rheumatology service at Children's Hospital in New Orleans. All patients satisfied the American College of Rheumatology criteria for the diagnosis of SLE. Paediatric SLE patients with cardiac manifestations based on echocardiogram were identified. Autoantibody tests at diagnosis were identified retrospectively by chart review, and the correlation between autoantibodies and cardiac involvement was analysed using the two tailed Fisher's exact test.
RESULTS—Thirteen (42%) of 31 SLE patients had cardiac manifestations of SLE. Seven (22%) had pericarditis without myocarditis, five (16%) had pericarditis and myocarditis, and one (3%) had myocarditis without pericarditis. Two patients (6%) with pericarditis had cardiac tamponade. Cardiac manifestations of SLE usually occurred at the time of diagnosis or within six months. Anti-Ro/SS-A antibodies were present in serum samples of nine of 11 (82%) patients with cardiac involvement and in five of 15 (33%) without cardiac involvement (p=0.02). Anti-La/SS-B antibodies were present in serum samples of six of 10 (60%) patients with cardiac involvement and two of 15 (13%) without cardiac involvement (p=0.03). Anti-Sm and anti-RNP antibodies showed no correlation with the presence of cardiac disease.
CONCLUSIONS—Cardiac involvement in our paediatric SLE population was frequently found and correlated significantly with the presence of anti-Ro/SS-A and anti-La/SS-B antibodies.