Genetics of susceptibility and severity in systemic lupus erythematosus

Serum/plasma homocysteine levels in patients with systemic lupus erythematosus: a systematic review and meta-analysis

Published studies have shown contradictory results in the association of serum/plasma levels of homocysteine (HCY) with systemic lupus erythematosus (SLE). This study is to systematically evaluate the association of serum/plasma HCY levels in SLE. A search was done using PubMed, Embase, Web of Science, and ScienceDirect databases up to 7 April 2019. Thirty-six articles including 2919 SLE patients and 3120 healthy controls were finally included in this meta-analysis. The HCY levels were significantly higher in SLE patients than in healthy controls (P < 0.001). The subgroup analysis revealed that Asian, African, Arab, Mixed, White and others as well as ages (< 35 and ≥ 35) had significant higher HCY levels in SLE patients than in the healthy controls. The study indicated that patients with disease activity index scores < 8 (P < 0.001) and ≥ 8 (P = 0.003) of SLE had significant higher HCY levels as compared with the healthy controls. It was also revealed that disease duration in SLE patients for < 10 and ≥ 10 years (P < 0.001) had significant higher HCY levels as compared with the healthy controls. A significant higher HCY level for body mass index (< 23 and ≥ 23) was found as well as measurement type in SLE patients than healthy controls. This meta-analysis demonstrated higher HCY levels in patients with SLE than healthy controls, suggesting a possible role of HCY in the disease.Key Points• Homocysteine (HCY) is closely related to the mechanisms of systemic lupus erythematosus (SLE).• This study reveals a significant correlation between HCY levels and the various indexes of disease activity.• This study reveals that medication may influence HCY levels in SLE.• This study also discovers that the subgroup analysis of all the factors influences the HCY levels in SLE patients.

Differential expression of the inflammasome complex genes in systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a complex autoimmune disorder involving heterogeneous clinical manifestations and numerous susceptibility genes. Several findings evidence the critical role of inflammasomes in the predisposition to autoimmune diseases and in SLE. We investigated whether inflammasome polymorphins could affect susceptibility to develop and/or severity SLE. Moreover, differences in inflammasome activation in peripheral blood were also evaluated in SLE patients and controls. The distribution of 13 SNPs in eight inflammasome genes was evaluated. To assess inflammasome priming in peripheral blood monocytes of SLE and controls, differential expression of selected inflammasome genes and IL-1ß production was analyzed in resting condition as well as after LPS and ATP stimulation. Results showed that the gain-of-function variant rs10754558 (NLRP3) was significantly more frequent in SLE patients with nephritis, reinforcing the concept of a key role of NLRP3 inflammasome not only in SLE but also especially in kidney disease. SLE monocytes in resting condition showed a higher level of IL-1ß expression and produced higher levels of IL-1ß when stimulated with LPS+ATP comparing to controls. The stimulation induced a significant expression of NLRP1, AIM2, CASP1, and IL1B genes, suggesting that the NLRP1 inflammasome is responsible for the IL-1ß production observed in monocytes. These data emphasized once more the important contribution of inflammasome in SLE-associated inflammation.

Microchimeric cells in systemic lupus erythematosus: targets or innocent bystanders?

During pregnancy maternal and fetal cells commute back and forth leading to fetal microchimerism in the mother and maternal microchimerism in the child that can persist for years after the birth. Chimeric fetal and maternal cells can be hematopoietic or can differentiate into somatic cells in multiple organs, potentially acting as targets for ‘autoimmunity' and so have been implicated in the pathogenesis of autoimmune diseases that resemble graft-versus-host disease after stem cell transplantation. Fetal cells have been found in women with systemic lupus erythematosus, both in the blood and a target organ, the kidney, suggesting that they may be involved in pathogenesis. Future studies will address how the host immune system normally tolerates maternal and fetal cells or how the balance may change during autoimmunity.

FcγRIIB Gene Polymorphisms Are Associated with Disease Risk and Clinical Manifestations of Systemic Lupus Erythematosus in Koreans

Systemic lupus erythematosus (SLE) is chronic autoimmune disease with various autoantibodies, which are involved in tissue damage. Fc gamma receptors (FcγRs) bind the constant region of the immunoglobulin G and transmit stimulatory or inhibitory signal to immune cells. The FcγR genes map to 1q23, a susceptible locus for SLE. We have screened single nucleotide polymorphisms (SNPs) in one of FcγR gene, FcγRIIB, which is the only inhibitory receptor, after considering gene map and reported SNPs. There were 3 SNPs in FcγRIIB: 10849 T>C (rs1050501) in exon 5 and 10950 T>G (rs6666965) and 11045 G>T (rs12117530) in intron 5 in Koreans. The frequency of the minor allele (T) of rs12117530 was significantly higher in SLE patients (50 patients, 20.4%) than healthy controls (17 patients, 12%, p = 0.041). Leukopenia occurred more frequently in SLE patients carrying the minor allele (T) of rs12117530 (p = 0.032). Among 5 haplotypes, the frequency of decreased complement was significantly lower in SLE patients with haplotype 1 [TTG] (p = 0.045). Nephritis, lymphopenia and anti-dsDNA antibody were significantly less frequent in SLE patients with haplotype 2 [TGG] (p = 0.046, p = 0.018, p = 0.002, respectively). The frequency of thrombocytopenia and anti-dsDNA antibody was significantly higher in SLE patients with haplotype 3 [CTG] (p < 0.001, p = 0.04, respectively). These data reveal that genetic polymorphisms within FcγRIIB are associated with disease susceptibility and phenotypes of SLE in Koreans. Furthermore, FcγRIIB rs12117530 polymorphism (T allele) may be an important risk factor in SLE.

Epigenetics in the treatment of systemic lupus erythematosus: potential clinical application

The current treatments of systemic lupus erythematosus (SLE) have been based on the use of immunosuppressive drugs which are linked to serious side effects. The more effective therapeutic approaches with minimal or no side effects for SLE patients are hard to develop, mainly due to the complexity of the disease. The discovery of pharmacoepigenetics provides a new way to solve this problem. Epigenetic modifications can influence drug efficacy by altering gene expression via changing chromatin structure. Although still in early development, epigenetic studies in SLE are expected to reveal novel therapeutic targets and disease biomarkers in autoimmunity. For example, miRNAs, which have been identified to govern many genes including drug targets, are altered in disease development and after drug administration. This review aims to present an overview of current epigenetic mechanisms involved in the pathogenesis of SLE, and discuss their potential roles in clinical and pharmacological applications.

Copy Number Variation of TLR-7 Gene and its Association with the Development of Systemic Lupus Erythematosus in Female Patients from Yucatan Mexico

Systemic lupus erythematosus (SLE) is a systemic autoimmune disease characterized by the production of autoantibodies against self-antigens, which occurs most often in women between 15 and 40 years of age. The innate immunity is involved in the pathogenesis of SLE through TLR- 7. Genetic factors such as copy number variation (CNV) of target genes may contribute to disease development, but this possible risk has not yet been studied in SLE patients from Yucatan, Mexico. The CNV of TLR-7 gene was determined by quantitative polymerase chain reaction assay using TaqMan probes in 80 SLE women and 150 control subjects. The results showed that 10% of SLE patients exhibited more than two copies of TLR-7 gene, whereas no mRNA overexpression was detected. These data suggested that increased CNV of the TLR-7 gene in Yucatan SLE women can be a risk factor for this disease.

Single-nucleotide Polymorphism and Haplotypes of TNIP1 Associated with Systemic Lupus Erythematosus in a Chinese Han Population

Objective.

To determine the association of systemic lupus erythematosus (SLE) with single-nucleotide polymorphisms (SNP) in the TNIP1 gene and compare the expression of this gene in cases and controls from a Chinese Han population in this replication study.

Methods.

Matrix-assisted laser desorption ionization time-of-flight mass spectrometry was used to genotype 19 SNP in TNIP1 in Chinese Han patients with SLE (n = 341) and controls (n = 356). Genotypes were analyzed by codominant, dominant, and recessive models. Analysis of allele frequencies and linkage disequilibrium was also performed. Western blotting and qRT-PCR were used to measure the expression of these genes in peripheral blood mononuclear cells of SLE cases and controls.

Results.

Seven SNP loci were significantly associated with SLE in our population (p < 0.05 for all comparisons). Two TNIP1 gene haplotypes (ATTGCGC and GTCCTAT) were associated with SLE (p = 0.0246 and p = 0.0024, respectively). Western blotting and qRT-PCR results provide evidence that patients with SLE had significantly reduced expression of TNIP1/ABIN-1 relative to controls.

Conclusion.

Analysis of SNP in the TNIP1 gene and expression of this gene in peripheral blood lymphocytes indicated these SNP were associated with the occurrence of SLE in Han Chinese patients. Future studies should examine the roles of these SNP in the pathogenesis of SLE.

Biomarkers for systemic lupus erythematosus

The urgent need for lupus biomarkers was demonstrated in September 2011 during a Workshop sponsored by the Food and Drug Administration: Potential Biomarkers Predictive of Disease Flare. After 2 days of discussion and more than 2 dozen presentations from thought leaders in both industry and academia, it became apparent that highly sought biomarkers to predict lupus flare have not yet been identified. Even short of the elusive biomarker of flare, few biomarkers for systemic lupus erythematosus (SLE) diagnosis, monitoring, and stratification have been validated and employed for making clinical decisions. This lack of reliable, specific biomarkers for SLE hampers proper clinical management of patients with SLE and impedes development of new lupus therapeutics. As such, the intensity of investigation to identify lupus biomarkers is climbing a steep trajectory, lending cautious optimism that a validated panel of biomarkers for lupus diagnosis, monitoring, stratification, and prediction of flare may soon be in hand.

No association between interleukin 23 receptor gene polymorphisms and systemic lupus erythematosus

The objective of this study was to elucidate whether polymorphisms of the interleukin 23 receptor gene (IL23R) are associated with susceptibility to systemic lupus erythematosus (SLE) in a Korean population. We recruited 602 SLE patients and 991 healthy controls. Seven single nucleotide polymorphisms (rs1004819, rs7517847, rs10489629, rs2201841, rs1343151, rs11209032, and rs1495965) were selected for genotyping among previously reported variants used in a genome-wide association study of inflammatory bowel disease. Polymorphic sites were genotyped using the TaqMan assay. The genotype distributions of IL23R polymorphisms and haplotypes were compared between the SLE patients and healthy controls using multiple logistic regression models. None of the IL23R genetic variants differed significantly between SLE patients and healthy controls, which suggests that IL23R polymorphisms play no role in the susceptibility to SLE in the Korean population. Electronic supplementary material The online version of this article (doi:10.1007/s00296-009-0893-8) contains supplementary material, which is available to authorized users.

Association between variable number tandem repeats within the 3' flanking region of the interleukin-6 gene and systemic lupus erythematosus in Korean patients

Variable number tandem repeat (VNTR) polymorphism located in the 3' flanking region of the interleukin-6 (IL-6) gene was examined in Koreans with systemic lupus erythematosus (SLE). We identified 15 VNTR alleles (K1 to K15) in the 3' flanking region by Genescan analysis. The VNTR K8 allele, a 648-base pair (bp) allele, was most commonly found in Koreans, being present in 74.8% of the SLE patients and 70.3% of the normal controls. The VNTR K9 (642 bp) allele was associated with susceptibility to SLE. In addition, the VNTR K9 was significantly associated with leukopenia (p = 0.048), thrombocytopenia (p = 0.020), and elevated C-reactive protein (p = 0.019). These data suggest that the VNTR K9 in the 3' flanking region of the IL-6 gene may be associated with disease susceptibility and the clinical phenotypes of SLE.

Systemic lupus erythematosus: association with KIR and SLC11A1 polymorphisms, ethnic predisposition and influence in clinical manifestations at onset revealed by ancestry genetic markers in an urban Brazilian population

Systemic lupus erythematosus (SLE) is an autoimmune disorder of the connective tissue with a wide and heterogeneous spectrum of manifestations, with renal and neurological involvement usually related to worse prognosis. SLE more frequently affects females of reproductive age, and a high prevalence and renal manifestation seem to be associated with non-European ethnicity. The present study aims to investigate candidate loci to SLE predisposition and evaluate the influence of ethnic ancestry in the disease risk and clinical phenotypic heterogeneity of lupus at onset. Samples represented by 111 patients and 345 controls, originated from the city of Belém, located in the Northern Region of Brazil, were investigated for polymorphisms in HLA-G, HLA-C, SLC11A1, MTHFR, CASP8 and 15 KIR genes, in addition to 89 Amerindian samples genotyped for SLC11A1. We also investigated 48 insertion/deletion ancestry markers to characterize individual African, European and Amerindian ancestry proportions in the samples. Predisposition to SLE was associated with GTGT deletion at the SLC11A1 3'UTR, presence of KIR2DS2 +/KIR2DS5 +/KIR3DS1 + profile, increased number of stimulatory KIR genes, and European and Amerindian ancestries. The ancestry analysis ruled out ethnic differences between controls and patients as the source of the observed associations. Moreover, the African ancestry was associated with renal manifestations.

Copy number variations of the human histamine H4 receptor gene are associated with systemic lupus erythematosus

BACKGROUND

Systemic lupus erythematosus (SLE) is a complex genetic disease; the histamine H4 receptor (HRH4) has been shown to be related to different kinds of autoimmune disorders; and copy number variations (CNVs) have been found to be associated with various types of diseases.

OBJECTIVES

To explore a possible association between HRH4 (formerly H4R) CNVs and the risk of SLE.

METHODS

Genomic DNA and RNA from 340 patients with SLE and 392 healthy controls were extracted, and CNVs and mRNA levels of HRH4 were examined.

RESULTS

The expression of HRH4 mRNA was significantly increased in patients with SLE compared with controls. Amplification of HRH4 copy numbers significantly increased the risk of SLE [P < 0·001, odds ratio (OR) 2·26, 95% confidence interval (CI) 1·50-3·40]. HRH4 amplifications also positively correlated with the incidence of arthritis (P = 0·019, OR 1·96, 95% CI 1·11-3·47), and proteinuria (P < 0·001, OR 2·95, 95% CI 1·73-5·00) and antinuclear antibody abnormalities (P < 0·001, OR 2·97, 95% CI 1·66-5·33). Deletions of HRH4 copy numbers were protective against proteinuria (P = 0·03, OR 0·50, 95% CI 0·26-0·94).

CONCLUSION

CNVs of the HRH4 gene are associated with SLE.

Interleukin 6 gene polymorphisms are associated with systemic lupus erythematosus in Koreans

OBJECTIVE

Interleukin 6 (IL-6) gene polymorphisms are known to play a role in chronic inflammatory disorders. We searched for polymorphisms in the IL-6 gene and described their pathogenic role in Korean patients with systemic lupus erythematosus (SLE).

METHODS

Genomic DNA was extracted from 151 patients with SLE and 151 controls, and about 1.4 kb-sized IL-6 genes located between promoter region and exon 2 region were amplified by polymerase chain reaction. The promoter activity was analyzed by luciferase reporter assay in Hep3B cells and HeLa cells.

RESULTS

We identified 4 single-nucleotide polymorphisms (SNP; -572 C > G, -278 A > C in the promoter, and 330 T > G, and 334 A > T in exon 2) and a -373 A(n)T(n) tract polymorphism in the IL-6 gene. The genotype frequency, -373 A(10)T(11), -278 C, and 334 T allele were significantly associated with SLE (p < 0.001, p = 0.03 and p = 0.005, respectively). Patients with SLE carrying the -572 G allele had anti-dsDNA more frequently (p = 0.007). In addition, thrombocytopenia was significantly more common in patients carrying the -278 C allele (p = 0.006). In the haplotype analysis, patients with SLE had more frequently haplotype HT3 (CA(10)T(11)ATA, dominant model, p = 0.012) that was associated with arthritis, leukopenia, anti-dsDNA, and hypocomplementemia. Promoter reporter structures carrying the -278 C allele displayed significantly higher promoter activity than the -278 A allele in Hep3B cells (p < 0.001) and HeLa cells (p < 0.001).

CONCLUSION

These data suggest that IL-6 gene polymorphisms are associated with disease susceptibility and phenotype of SLE. In addition, promoter polymorphisms may be involved in regulation of IL-6 expression.

Association of the genetic polymorphisms of the ACE gene and the eNOS gene with lupus nephropathy in northern Chinese population

BACKGROUND

It has been reported that some single nucleotide polymorphisms (SNPs) of the angiotensin converting enzyme (ACE) gene and the endothelial nitric oxide synthase (eNOS) gene are associated with the development of systemic lupus erythematosus (SLE) and the progression of nephropathy. The aim of this study was to evaluate the possible association between six SNPs (A-5466C, T-3892C, A-240T, C1237T, G2215A and A2350G) of the ACE gene and two SNPs (T-786C and G894T) of the eNOS gene with lupus nephropathy in a northern Chinese population.

METHODS

In this study, 225 patients with lupus nephropathy were compared to 232 healthy controls, matched by gender, age and ethnicity. Following the extraction of genomic DNA from the leukocytes in the peripheral blood, the genotypes of the eight selected SNPs were determined by the method of PCR-RFLP; the haplotypes were inferred using PHASE 2.1. The associations between the SNPs and the risk of lupus nephropathy were analyzed using Chi-square test and Logistic regression with SPSS13.0 software.

RESULTS

Statistically significant differences of the allele frequency distribution of three SNPs (A-5466C, A2350G and G894T) were observed between cases and controls (P<0.05). Among the 53 haplotypes identified, the frequencies of five haplotypes (CTTCGA, ACTTAA, ACATGG, ACACGG and ATTCGA) were significantly different between cases and controls (P<0.05).

CONCLUSIONS

Our study indicated an association between the risk of lupus nephropathy and the sequence variations of both the ACE gene and the eNOS gene, which may play an important role in the pathogenesis of lupus nephropathy in the northern Chinese population. Further studies are warranted to validate our findings.

Systemic lupus erythematosus and ethnicity: nature versus nurture or nature and nurture?

Ethnic variation in the frequency and outcome of systemic lupus erythematosus (SLE) has been recognized for decades. The reasons underlying these discrepancies are not completely understood but it is most likely that both genetic and nongenetic factors are responsible for them. Sorting out the extent to which these factors, particularly those of a nongenetic nature, exert their influence in SLE is not easy given inherent methodological difficulties in studying them. To establish this review properly, we would like to make it clear from the outset that ethnicity is a broad construct that implies not only biological but also nonbiological features including cultural and sociodemographic, among others. We will then describe the epidemiological differences of SLE among Caucasian and non-Caucasian populations followed by a succinct review of the genetic predisposition to SLE with special emphasis in ethnic heterogeneity. Differences in disease activity, lupus nephritis, damage and mortality as a function of ethnic group will then be described. Finally, we will present a comprehensive model of the influence of ethnicity on SLE.

The search for lupus biomarkers

Few biomarkers for systemic lupus erythematosus (SLE) have been validated and employed for making clinical decisions. The lack of reliable, specific biomarkers for SLE hampers the proper clinical management of patients with SLE and impedes the development of new lupus therapeutics. This void has led to renewed enthusiasm for identifying biomarkers that precisely and specifically reflect the pathophysiological and clinical changes of SLE. Several laboratory markers have shown early promise as biomarkers for lupus susceptibility, diagnosis and monitoring. These include polymorphisms and copy-number variations of complement C4 and Fcgamma receptor genes (disease susceptibility), cell-bound complement C4d (diagnosis and/or disease activity), CD27(high) plasma cells (disease activity), 'interferon signature' (disease activity) and anti-C1q and anti-NMDA (disease activity and organ involvement). Although these and other promising candidate biomarkers have been identified, they still need to be validated through rigorous, large-scale multicentre studies. This article briefly reviews the historical aspects of lupus biomarkers and summarises current efforts to advance the field.

C-Reactive Protein Gene Polymorphisms in Disease Susceptibility and Clinical Manifestations of Korean Systemic Lupus Erythematosus

Objective.

C-reactive protein (CRP) is a sensitive marker of inflammation. It is hypothesized that polymorphism of CRP gene contributes to susceptibility to systemic lupus erythematosus (SLE). We tested this hypothesis by identifying CRP gene polymorphisms in Korean patients with SLE.

Methods.

Approximately 1.5 kb of CRP promoter region was screened for single nucleotide polymorphism (SNP) using direct sequencing and 3 SNP in CRP exons by restriction fragment length polymorphism. The basal levels of CRP were measured by immunoturbidimetry. The effect of −390 C>A or T polymorphism on the promoter activity was analyzed by luciferase reporter assay in Hep3B cells.

Results.

Allele frequency at polymorphisms within CRP promoter and exon in our Korean patients with SLE differed from that of Caucasians. The A allele was a major allele at position 2043 in Korean SLE patients, whereas G is a major allele in Caucasian SLE. Our SLE patients had minor allele in the −390 polymorphism more frequently versus controls (p = 0.033). CRP 1185 polymorphism was associated with thrombocytopenia (p = 0.043). The basal levels of CRP were significantly higher in individuals who had minor allele in −390 and 2043 polymorphisms (p = 0.03. p = 0.024, respectively). Promoter-reporter construct carrying the −390 A or T allele displayed significantly higher promoter activity than that with the −390 C allele (p < 0.001).

Conclusion.

CRP gene −390 polymorphism plays a role in disease susceptibility of SLE through regulation of serum CRP level. Our results suggest that elevated basal CRP level may be important in the pathogenesis of SLE, even though CRP responsiveness to noninfectious inflammation of SLE is decreased.

Microarray analysis of autoimmune diseases by machine learning procedures

Microarray-based global gene expression profiling, with the use of sophisticated statistical algorithms is providing new insights into the pathogenesis of autoimmune diseases. We have applied a novel statistical technique for gene selection based on machine learning approaches to analyze microarray expression data gathered from patients with systemic lupus erythematosus (SLE) and primary antiphospholipid syndrome (PAPS), two autoimmune diseases of unknown genetic origin that share many common features. The methodology included a combination of three data discretization policies, a consensus gene selection method, and a multivariate correlation measurement. A set of 150 genes was found to discriminate SLE and PAPS patients from healthy individuals. Statistical validations demonstrate the relevance of this gene set from an univariate and multivariate perspective. Moreover, functional characterization of these genes identified an interferon-regulated gene signature, consistent with previous reports. It also revealed the existence of other regulatory pathways, including those regulated by PTEN, TNF, and BCL-2, which are altered in SLE and PAPS. Remarkably, a significant number of these genes carry E2F binding motifs in their promoters, projecting a role for E2F in the regulation of autoimmunity.

Pathophysiology and clinical spectrum of infections in systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is an inflammatory and multisystemic autoimmune disorder characterized by an uncontrolled autoreactivity of B and T lymphocytes leading to the production of autoantibodies against self-directed antigens and tissue destruction. Environmental factors, such as infections, which are an important cause of morbidity and mortality, are potential triggers of the disease. This article discusses bacterial, viral, and opportunistic microorganism infections in SLE, and the role of immunosuppressive therapy and immunodeficiencies in the disease.

Fcgamma receptors: structure, function and role as genetic risk factors in SLE

Over 30 years ago, receptors for the Fc region of IgG (FcgammaR) were implicated in the pathogenesis of systemic lupus erythematosus (SLE). Since those pioneering studies, our knowledge of the structure and function of these FcgammaRs has increased dramatically. We now know that FcgammaR contributes to the regulation of acquired immunity and to the regulation of innate immune responses where FcgammaRs act as specific receptors for innate opsonins (CRP and SAP). Our understanding of the genomic architecture of the genes encoding the FcgammaR has also witnessed remarkable advances. Numerous functionally relevant single-nucleotide polymorphism (SNP) variants and copy number (CN) variants have been characterized in the FcgammaR genes. Many of these variants have also been shown to associate with risk to development of SLE and some have been associated with disease progression. This review will provide an overview of the FcgammaR in relation to SLE, including consideration of the role of genetic variants in FcgammaR in SLE pathogenesis. The difficulties in assessing genetic variation in these genes will be discussed. To enhance our understanding of the functional roles of these receptors in SLE, future research will need to integrate our knowledge of SNP variants, CN variants and the functional diversity of these receptors.

Glu298Asp eNOS polymorphism is not associated with SLE

To examine potential associations of the Glu298Asp polymorphism in the coding region of the endothelial nitric oxide synthase (eNOS) gene with susceptibility to and clinical expression of systemic lupus erythematosus (SLE). One hundred thirteen consecutive patients of European ancestry with diagnosis of SLE, satisfying the American College of Rheumatology criteria, from the outpatient clinic of the Serviço de Reumatologia of the Hospital de Clínicas de Porto Alegre, and 206 healthy controls from the same geographic area were genotyped by polymerase chain reaction for the Glu298Asp polymorphism in the coding region of the eNOS gene. Clinical, demographic, and laboratorial data were collected. Clinical manifestations of SLE and related diseases were evaluated for the association with specific genotypes. The allelic and genotypic distribution of the Glu298Asp did not differ significantly between SLE patients and controls. We found no association of the polymorphism with lupus nephritis, antiphospholipid syndrome, cardiovascular disease (CVD), and risk factors to CVD. The presented results in this study do not provide support for a major role of eNOS Glu298Asp neither in the susceptibility for SLE or clinical manifestations, although there was low statistical power for the latter evaluation.

Copy number variants in genetic susceptibility and severity of systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a systemic autoimmune disorder characterized by the presence of auto-antibodies to nuclear antigens, immune complex deposition, and subsequent tissue destruction. Early studies in twins suggested that SLE has, at least in part, a genetic basis, and a role for class II alleles in the major histocompatibility complex has been known for over 30 years. Through both linkage studies and candidate gene studies, numerous additional genetic risk factors have been identified. The recent publication of two SNP-based genome-wide association studies (GWAS) has resulted in the confirmation of a number of previously identified genetic risk loci and has identified new previously unappreciated loci conferring risk for development of SLE. A role for gene copy number variation (CNV) in SLE has also been appreciated through studies of the complement component 4 (C4) loci and more recent work in the IgG Fc receptor loci. The availability of large SNP-based GWAS datasets will undoubtedly lead to the genome-wide analysis and identification of copy number variants related to genetic susceptibility for development of SLE. We review current studies of CNV in SLE susceptibility that include reports of association between SLE and CNV in C4, IgG Fc receptors, TLR7, and CCL3L1.

Time to seizure occurrence and damage in PROFILE, a multi-ethnic systemic lupus erythematosus cohort

The objective of this study was to determine risk factors predicting seizures and damage caused by seizures in a multi-ethnic systemic lupus erythematosus cohort (PROFILE) that includes systemic lupus erythematosus patients (n = 1295) from five different US institutions. Only patients with seizures after systemic lupus erythematosus diagnosis (incident) were included in the analyses of clinical seizures (80/1295, 6.2%), but all patients (prevalent and incident) were included in the analyses of damage caused by seizures (51/1295, 3.9%). We examined socioeconomic-demographic, clinical, and genetic variables predictive of clinical seizures and damage from seizures by Cox proportional hazard ratios (HR) and 95% confidence intervals (CI). Independent predictors of a shorter time to the occurrence of clinical seizures were younger age (HR = 1.0; 95% CI 0.9-1.0), having Hispanic-Texan ethnicity (HR = 2.7; 95% CI 1.3-5.7) or African-American ethnicity (HR = 1.8; 95% CI 1.0-3.1), and the previous occurrence of a cerebrovascular accident (HR = 3.3; 95% CI 1.6-7.1) or an episode of psychosis (HR = 2.4; 95% CI 1.1-5.0), whereas the previous occurrence of photosensitivity (HR = 0.5; 95% CI 0.3-0.9) was the only independent predictor of a longer time to the occurrence of clinical seizures. Independent predictors of a shorter time to the occurrence of damage caused by seizures were younger age (HR = 1.0; 95% CI 0.9-1.0), male gender (HR = 2.4; 95% CI 1.1-5.4), and the occurrence of a previous cerebrovascular accident (HR = 2.7; 95% CI 1.0-7.0) or an episode of psychosis (HR = 4.7; 95% CI 2.3-9.9). No allele from the candidate genes examined (HLA-DRB1, HLA-DQB1, FCGR2A, FCGR3A, or FCG3B) predicted clinical seizures or damage caused by seizures.

Natural regulatory T cells: number and function are normal in the majority of patients with lupus nephritis

CD4(+) CD25(+) regulatory T cells have been shown to be a vital component of the mechanisms that prevent autoreactivity in mice and also in humans. Previous studies have examined CD4(+) CD25(hi) regulatory T cell frequency and function in patients with systemic lupus erythematosus (SLE) with mixed results. We investigated frequency, phenotype and function in 21 patients with SLE and six with inactive disease. We found no reduction in frequency of the CD25(hi) subset, although active disease was associated with an increased proportion of CD4(+) CD25(+) T cells. When examining function, in the majority of individuals suppression was comparable with controls, although cells isolated from one patient with active disease failed to suppress proliferation. On testing the effect of CD25(hi) depletion on the responses of whole peripheral blood mononuclear cells to nucleosomes we found that, where a response was detectable from patients, depletion augmented interferon-gamma secretion, demonstrating intact suppression of responses implicated in the pathogenesis of SLE. Our results did not confirm an association of failure in CD4(+) CD25(hi) regulatory T cell function or a reduction in their frequency with active disease. Instead, perturbations in the CD4(+) CD25(hi) regulatory T cell population may play a role in disease in only a minority of the patients afflicted by the diverse syndromes of SLE.

Fc receptor genes and the systemic lupus erythematosus diathesis

Fc receptors represent a distinct group of hematopoeitic cell surface glycoproteins that have a characterized role in affecting the efficiency of the mononuclear phagocyte system to clear IgG immune complexes. Functional genetic variations in this family of receptors have been identified as heritable susceptibility factors for SLE and lupus nephritis across diverse populations. In this review, we describe the roles of the classical Fc receptors for IgG (Fc gamma) and non-classical Fc-like receptors (FCR1-FCRL6L), Fc receptors for IgE (Fc epsilon RI) and IgA and IgM (Fc alpha/mu R) in SLE diathesis. The combined effects of these genes on SLE pathogenesis, either via linkage disequilibrium or epistasis with additional genetic or environmental factors, provide a challenge for future investigations. The pursuit of a polygenic SLE-profile that includes longitudinal evaluations of SLE and markers involved in the protean clinical manifestations associated with SLE will facilitate our understanding of the cascade of inflammatory events associated with the diathesis.

The role of mannose-binding lectin in systemic lupus erythematosus

Susceptibility to systemic lupus erythematosus (SLE) is associated with genetic, hormonal, immunological, and environmental factors. Many genes have been related with the appearance of SLE, including several loci that code different complement components and their receptors. Some genetic deficiencies of complement molecules are strongly associated with SLE, probably because these deficiencies could cause decreased clearance of apoptotic cell material. As a consequence of the apoptotic material accumulation, high levels of autoantigens can be presented inappropriately to the immune system in an inflammatory context, resulting in an imbalance on the mechanisms of immunological tolerance, immune system activation, and autoantibody production. Recent studies proposed a role to the mannose-binding lectin (MBL) in the SLE physiopathogenesis. This protein activates the complement system, and the presence of several polymorphisms at the promoter and coding regions of the MBL-2 gene determines alterations at the plasma levels of MBL. Some of these polymorphisms have been associated with SLE susceptibility, as well as with clinical and laboratory typical features of this disease, cardiovascular events, and infections. Besides, it has been described that the presence of anti-MBL autoantibodies in sera of SLE patients can influence MBL plasma levels and its functional activity.

Association of a CD24 gene polymorphism with susceptibility to systemic lupus erythematosus

OBJECTIVE

To determine the potential role of the CD24 A57V gene polymorphism in systemic lupus erythematosus (SLE).

METHODS

We studied 3 cohorts of Caucasian patients and controls. The Spanish cohort included 696 SLE patients and 539 controls, the German cohort included 257 SLE patients and 317 controls, and the Swedish cohort included 310 SLE patients and 247 controls. The CD24 A57V polymorphism was genotyped by polymerase chain reaction, using a predeveloped TaqMan allele discrimination assay. Odds ratios (ORs) and 95% confidence intervals (95% CIs) were calculated.

RESULTS

In the Spanish cohort there was a statistically significant difference in the distribution of the CD24 V allele between SLE patients and controls (OR 3.6 [95% CI 2.13-6.16], P < 0.0001). In addition, frequency of the CD24 V/V genotype was increased in SLE patients compared with controls (OR 3.7 [95% CI 2.16-6.34], P < 0.00001). We sought to replicate this association with SLE in a German population and a Swedish population. A similar trend was found in the German group. The CD24 V/V genotype and the CD24 V allele were more frequent in SLE patients than in controls, although this difference was not statistically significant. No differences were observed in the Swedish group. A meta-analysis of the Spanish and German cohorts demonstrated that the CD24 V allele has a risk effect in SLE patients (pooled OR 1.25 [95% CI 1.08-1.46], P = 0.003). In addition, homozygosity for the CD24 V risk allele significantly increased the effect (pooled OR 2.19 [95% CI 1.50-3.22], P = 0.00007).

CONCLUSION

These findings suggest that the CD24 A57V polymorphism plays a role in susceptibility to SLE in a Spanish population.

Analysis of interleukin-23 receptor (IL23R) gene polymorphisms in systemic lupus erythematosus

The aim of this study was to evaluate the association between systemic lupus erythematosus (SLE) and polymorphisms in the interleukin-23 receptor (IL23R) gene, which have been previously found to be associated with two autoimmune diseases: inflammatory bowel disease and psoriasis. Our study includes 224 SLE patients and 342 healthy controls. The genotyping of IL23R variants was carried out using a polymerase chain reaction system with predeveloped TaqMan allelic discrimination assays. No statistically significant differences were observed between SLE patients and healthy controls with any of the IL23R genetic variants. In addition, we did not find any significant differences when we stratified SLE patients according to their clinical and demographic features. These results suggest that IL23R polymorphisms do not appear to play an important role in the susceptibility or severity of SLE in the Spanish population.

Opposed independent effects and epistasis in the complex association of IRF5 to SLE

Genetic variation in the interferon regulatory factor 5 (IRF5) gene affects systemic lupus erythematosus (SLE) susceptibility. However, association is complex and incompletely defined. We obtained fourteen European sample collections with a total of 1383 SLE patients and 1614 controls to better define the role of the different IRF5 variants. Eleven polymorphisms were studied, including nine tag single nucleotide polymorphisms (SNPs) and two extra functional polymorphisms. Two tag SNPs showed independent and opposed associations: susceptibility (rs10488631, P<10(-17)) and protection (rs729302, P<10(-6)). Haplotype analyses showed that the susceptibility haplotype, identified by the minor allele of rs10488631, can be due to epistasis between three IRF5 functional polymorphisms. These polymorphisms determine increased mRNA expression, a splice variant with a different exon 1 and a longer proline-rich region in exon 6. This result is striking as none of the three polymorphisms had an independent effect on their own. Protection was independent of these polymorphisms and seemed to reside in the 5' side of the gene. In conclusion, our results help to understand the role of the IRF5 locus in SLE susceptibility by clearly separating protection from susceptibility as caused by independent polymorphisms. In addition, we have found evidence for epistasis between known functional polymorphisms for the susceptibility effect.

Gene copy-number variation and associated polymorphisms of complement component C4 in human systemic lupus erythematosus (SLE): low copy number is a risk factor for and high copy number is a protective factor against SLE susceptibility in European Americans

Interindividual gene copy-number variation (CNV) of complement component C4 and its associated polymorphisms in gene size (long and short) and protein isotypes (C4A and C4B) probably lead to different susceptibilities to autoimmune disease. We investigated the C4 gene CNV in 1,241 European Americans, including patients with systemic lupus erythematosus (SLE), their first-degree relatives, and unrelated healthy subjects, by definitive genotyping and phenotyping techniques. The gene copy number (GCN) varied from 2 to 6 for total C4, from 0 to 5 for C4A, and from 0 to 4 for C4B. Four copies of total C4, two copies of C4A, and two copies of C4B were the most common GCN counts, but each constituted only between one-half and three-quarters of the study populations. Long C4 genes were strongly correlated with C4A (R=0.695; P<.0001). Short C4 genes were correlated with C4B (R=0.437; P<.0001). In comparison with healthy subjects, patients with SLE clearly had the GCN of total C4 and C4A shifting to the lower side. The risk of SLE disease susceptibility significantly increased among subjects with only two copies of total C4 (patients 9.3%; unrelated controls 1.5%; odds ratio [OR] = 6.514; P=.00002) but decreased in those with > or =5 copies of C4 (patients 5.79%; controls 12%; OR=0.466; P=.016). Both zero copies (OR=5.267; P=.001) and one copy (OR=1.613; P=.022) of C4A were risk factors for SLE, whereas > or =3 copies of C4A appeared to be protective (OR=0.574; P=.012). Family-based association tests suggested that a specific haplotype with a single short C4B in tight linkage disequilibrium with the -308A allele of TNFA was more likely to be transmitted to patients with SLE. This work demonstrates how gene CNV and its related polymorphisms are associated with the susceptibility to a human complex disease.

Programmed Death-1 Gene Polymorphisms in Patients With Systemic Lupus Erythematosus in Taiwan

To investigate the role of programmed cell death-1 (PD-1) gene polymorphisms in the development of systemic lupus erythematosus (SLE) in Taiwan, 109 patients with SLE and 100 healthy controls were enrolled in this study. The PD-1 gene polymorphisms were determined by the method of polymerase chain reaction/restriction fragment length polymorphism. This study showed that the genotype distributions of PD-1 7209 C/T polymorphisms were significantly different between the patients with SLE and controls (P=0.002, Pc=0.018). The frequencies of the PD-1 7209 C/C genotype and PD-1 7209 C allele were significantly higher in the patients with SLE than those of the controls (P=0.001, OR=2.6, 95% CI=1.5-4.6, and P=0.002, OR=2.1, 95% CI=1.3-3.4, Pc=0.018, respectively). Moreover, the association of PD-1 7209 C with susceptibility to SLE was independent of the PD-1 ligand. This study also showed that the PD-1-536 A 7146 G 7209 C 7499 G haplotype was associated with the development of SLE in Taiwan.

Systemic lupus erythematosus: all roads lead to type I interferons

In recent years, the study of systemic lupus erythematosus (SLE) patients has revealed a central role for type I interferon (IFN) in disease pathogenesis. IFN induces the unabated activation of peripheral dendritic cells, which select and activate autoreactive T cells rather than deleting them, thus failing to induce peripheral tolerance. IFN also directly affects T cells and B cells. Furthermore, immune complexes binding to FcgammaR and Toll-like receptors provide an amplification loop for IFN production and B-cell activation in SLE. Polymorphisms in genes that control IFN production or its downstream signaling pathway, such as IRF5, might be responsible for some of these alterations. This novel information is leading to the development of IFN antagonists as a potential therapeutic intervention in SLE, thus bringing hope to SLE patients.

Time to renal disease and end-stage renal disease in PROFILE: a multiethnic lupus cohort

BACKGROUND

Renal involvement is a serious manifestation of systemic lupus erythematosus (SLE); it may portend a poor prognosis as it may lead to end-stage renal disease (ESRD). The purpose of this study was to determine the factors predicting the development of renal involvement and its progression to ESRD in a multi-ethnic SLE cohort (PROFILE).

METHODS AND FINDINGS

PROFILE includes SLE patients from five different United States institutions. We examined at baseline the socioeconomic-demographic, clinical, and genetic variables associated with the development of renal involvement and its progression to ESRD by univariable and multivariable Cox proportional hazards regression analyses. Analyses of onset of renal involvement included only patients with renal involvement after SLE diagnosis (n = 229). Analyses of ESRD included all patients, regardless of whether renal involvement occurred before, at, or after SLE diagnosis (34 of 438 patients). In addition, we performed a multivariable logistic regression analysis of the variables associated with the development of renal involvement at any time during the course of SLE. In the time-dependent multivariable analysis, patients developing renal involvement were more likely to have more American College of Rheumatology criteria for SLE, and to be younger, hypertensive, and of African-American or Hispanic (from Texas) ethnicity. Alternative regression models were consistent with these results. In addition to greater accrued disease damage (renal damage excluded), younger age, and Hispanic ethnicity (from Texas), homozygosity for the valine allele of FcgammaRIIIa (FCGR3A*GG) was a significant predictor of ESRD. Results from the multivariable logistic regression model that included all cases of renal involvement were consistent with those from the Cox model.

CONCLUSIONS

Fcgamma receptor genotype is a risk factor for progression of renal disease to ESRD. Since the frequency distribution of FCGR3A alleles does not vary significantly among the ethnic groups studied, the additional factors underlying the ethnic disparities in renal disease progression remain to be elucidated.

Autoimmunity in systemic lupus erythematosus: integrating genes and biology

Susceptibility to the autoimmune phenotype of systemic lupus erythematosus (SLE) is heritable. Linkage analysis and recent advances in the field of single nucleotide polymorphisms (SNPs) have resulted in the identification of several genetic loci and functional allelic variants of signaling proteins which have become the mainstay of understanding disease susceptibility and exploring the basis of autoimmunity in SLE. However, genetic heterogeneity and possible epistatic interactions among genetic elements have precluded replication of these findings in multiple population groups and thus complicated their interpretation. In this regard, the discovery that a plethora of normal signaling proteins are expressed in abnormal amounts in immune cells from patients with SLE has gained significance. Thus, the key to precise elucidation of the pathologic basis of autoimmunity in SLE lies in tying genetics and disease biology. This review highlights recent discoveries of important functional genetic variants and altered expression of normal signaling proteins that network together to disrupt peripheral tolerance and initiate the autoimmune process in SLE.

Evidence of association of macrophage migration inhibitory factor gene polymorphisms with systemic lupus erythematosus

The aim of this study was to evaluate the potential association of functional polymorphisms of macrophage migration inhibitory factor with systemic lupus erythematosus. Our study includes 711 systemic lupus erythematosus (SLE) patients and 755 healthy controls. We genotyped the migration inhibitory factor (MIF) -173G/C using a polymerase chain reaction (PCR) system with predeveloped TaqMan allelic discrimination assay and the MIF -794 CATT(n) microsatellite polymorphism using a PCR-fluorescent method. A statistically significant difference in the distribution of the MIF -173(*)C allele between SLE patients and controls (P=0.004, OR=1.34, 95% CI=1.05-1.27) was observed. In addition, the frequency of the MIF -173(*)C/C genotype was higher in SLE patient (P=0.002, OR=2.58, 95% CI=1.32-5.10). No differences in the distribution of CATT(n) were found. However, the haplotypes analyses showed that only the CATT(7)-MIF -173(*)C haplotype was associated with a higher susceptibility to SLE (P=0.001, OR 1.84, 95% CI 1.35-2.79). No association with clinical features was detected in any case. These results suggest that both, MIF -173(*)C allele and CATT(7)-MIF -173(*)C haplotype, confer susceptibility to SLE in our population.

Analysis of a functional BTNL2 polymorphism in type 1 diabetes, rheumatoid arthritis, and systemic lupus erythematosus

The aim of this study was to test whether the functional variant rs2076530 of the BTNL2 gene confers susceptibility to the autoimmune diseases type 1 diabetes (T1D), rheumatoid arthritis (RA), and systemic lupus erythematosus (SLE). Our study populations consisted of 326 patients with T1D and 351 healthy subjects, 808 patients with RA and 1137 healthy controls, and 372 patients with SLE and 280 healthy controls. Genotyping of the BTNL2 gene rs2076530 polymorphism was performed by real-time polymerase chain reaction technology, using the TaqMan 5'-allele discrimination assay. We observed statistically significant differences in the distribution of BTNL2rs2076530 alleles between patients with T1D, RA, and SLE and healthy controls (p=0.0035, 0.000003, and 0.00002, respectively), but in two divergent ways: the G allele was associated with T1D and RA, and the A allele was associated with SLE. However, the polymorphism exhibited strong linkage disequilibrium with HLA DQB1-DRB1 haplotypes previously identified as predisposing to the diseases. When the BTNL2 polymorphism was tested conditional on HLA DQB1-DRB1haplotypes, the BTNL2 effect was no longer significant in all three study populations. The BTNL2 rs2076530 polymorphism is associated with T1D, RA, and SLE because of its strong linkage disequalibrium with predisposing HLA DQB1-DRB1 haplotypes in Caucasian populations.

SLE: challenges and candidates in human disease

Systemic lupus erythematosus (SLE) is an autoimmune disease characterized by immunological hyperactivity and multi-system organ damage. A complex genetic trait involving multiple genes, with both genetic heterogeneity and a threshold effect for disease expression, SLE involves abnormalities of both the innate and adaptive immune systems. Recognition of an 'interferon signature' in SLE leukocytes, of the role of B cells in promoting disease activity, and of FCGR3A alleles as a biomarker of end organ damage, provide important insights into disease pathogenesis. Nonetheless, coordinated studies in humans and model systems hold promise for an even more rapid advance in understanding pathways of disease development and strategies for intervention. More effective markers of disease risk, disease activity, severity of organ damage and outcomes would facilitate earlier diagnosis and guide appropriately targeted treatment.