Polymorphism at the C-reactive protein locus influences gene expression and predisposes to systemic lupus erythematosus

Relative deficiency of pentraxin proteins is implicated in the pathogenesis of systemic lupus erythematosus. The C-reactive protein (CRP) response is defective in patients with acute flares of disease, and mice with targeted deletions of the serum amyloid P component gene (Sap) develop a lupus-like illness. In humans, the genes for CRP (CRP) and SAP (APCS) map to 1q23.2 within an interval linked with SLE. We have investigated the candidate genes CRP and APCS in two cohorts totalling 586 UK simplex SLE families. The inheritance of an intronic dinucleotide repeat and seven single nucleotide polymorphisms in the CRP and APCS genes was examined by application of family-based tests of association and linkage. Basal levels of CRP were influenced independently by two polymorphisms at the CRP locus, CRP 2 and CRP 4. Furthermore, the latter polymorphism was linked/associated with SLE and antinuclear autoantibody production. Thus, the polymorphism associated with reduced basal CRP was also associated with the development of SLE. These data support the hypothesis that defective disposal of potentially immunogenic material is a contributory factor in lupus pathogenesis. The identification of polymorphisms that determine basal CRP levels has implications in ischaemic heart disease, where CRP level is an important predictor of risk.     

Interferon-gamma polymorphisms in systemic lupus erythematosus

Interferon-gamma is a cytokine which is believed to play a role in both the susceptibility and pathogenesis of lupus. To determine whether genetic variants might influence the development of this polygenic autoimmune disease, we analyzed the gene frequency of eight different alleles in controls and patients with SLE. Ninety-nine controls and 136 patients with systemic lupus erythematosus were genotyped for a CA repeat in the first intron of the interferon-gamma gene. There were no statistically significant differences in the allele frequencies between patients and controls suggesting that these polymorphic variants do not influence susceptibility. We then examined whether any of these alleles were associated with specific clinical manifestations. Allele 1 was associated with gastrointestinal lupus while allele 6 was associated with more severe lupus. Allele 2 appeared to be protective for arthritis. This suggests that genetic variation in interferon-gamma expression might influence the disease course.     

Vaccination against meningococcus in complement-deficient individuals

Autoantibodies to CRP were reported previously in patients suffering from toxic oil syndrome. This syndrome resembles autoimmune diseases such as systemic lupus erythematosus (SLE) or systemic scleroderma. We therefore examined the prevalence of antibodies to CRP and other acute-phase proteins in autoimmune diseases, including SLE, subacute cutaneous lupus erythematosus (SCLE), systemic scleroderma (SSc), and primary biliary cirrhosis (PBC), as well as in bone marrow transplantation-induced chronic graft-versus-host disease and eosinophilia–myalgia syndrome. IgG antibodies to CRP were found in 78% of SLE and in 30% of SCLE patients, while 16% of patients with PBC were positive. In up to 45% of patients with SSc predominantly IgG antibodies to ceruloplasmin were detectable. Lack of systemic involvement as in discoid lupus erythematosus and localized scleroderma (morphea) correlated with low or absent antibody formation. However, no correlation was found between anti-acute-phase protein antibodies with liver disease or other organ involvement. Adsorption studies revealed that non-native epitopes on the CRP molecule, termed modified CRP, are the main target of antibodies. Chronic inflammatory tissue injury in systemic autoimmune disease might increase the presentation of cryptic epitopes of CRP to the threshold required for T cell activation.     

Genetic variation in the CRP promoter: association with systemic lupus erythematosus

The pentraxin C-reactive protein (CRP), an innate immune system opsonin which binds nuclear debris and apoptotic bodies, may protect against autoimmunity. A relative deficiency of CRP levels in patients with systemic lupus erythematosus (SLE) might contribute to altered handling of self-antigens. We report that the proximal 5' promoter region of CRP contains several polymorphisms that exhibit association with SLE in multiple populations. Strongest association was observed at the proximal promoter single nucleotide polymorphism (SNP) rs3093061 (CRP-707) (P = 6.41 x 10(-7) and P = 2.13 x 10(-6) in African-American and Caucasian case-control samples respectively). This association remains after adjustment for admixture. Linkage disequilibrium exists between SNPs in the proximal promoter and association of functional haplotypes containing rs3091244/rs3093062 (CRP-409/-390) appear to be driven by the rs3093061 (CRP-707) association. These data demonstrate that rs3093061 at the -707 site within the CRP gene is an SLE susceptibility locus.     

CRP and the disposal of dying cells: consequences for systemic lupus erythematosus and rheumatoid arthritis

C reactive protein (CRP) levels directly correlate with the disease activity of many inflammatory diseases, e.g. sepsis, infection, and various autoimmunopathies such as rheumatoid arthritis (RA). In contrast, insufficient CRP levels are implicated in the development of systemic lupus erythematosus (SLE). This article reports on the level-depended effects of CRP in various diseases. In detail we show that increased and decreased levels of CRP, as demonstrated in patients with RA and SLE, respectively can contribute to disease progression.     

Immune interferon in the circulation of patients with autoimmune disease.

The observation that type II, or immune, interferon could be produced by peripheral-blood leukocytes in vitro on an immune-specific basis suggested that it also might be produced in vivo in various autoimmune disorders. We found immune interferon in the serums of patients with systemic lupus erythematosus, rheumatoid arthritis, scleroderma and Sj?gren's syndrome. Among 28 patients with systemic lupus erythematosus, 71 per cent of those with active and 21 per cent of those with inactive disease showed interferon in their serums. Serial serum samples showed a good correlation between interferon titers and disease activity. Moreover, interferon titers correlated positively with antibodies to DNA and negatively with serum levels of the third component of complement. It is possible that the production of interferon may contribute to immunologic aberrations in auto-immune diseases and also protect the already compromised host from viral infections.     

Quantification of the Genetic Component of Basal C-Reactive Protein Expression in SLE Nuclear Families

C-reactive protein (CRP) is a heritable acute-phase plasma protein also expressed at low, basal, levels in healthy individuals. Elevated basal CRP has been associated with increased cardiovascular risk, while CRP dysregulation may be a feature of systemic lupus erythematosus (SLE). In this cohort of 496 Caucasian SLE families we estimated basal CRP heritability, h²= 27.7%. We typed a dense map of CRP single nucleotide polymorphisms (SNPs) and found that seven were associated with basal CRP using both a regression approach and an orthogonal family-based test (P = 0.001–0.011), as were haplotypes carrying the minor allele of these SNPs. SNPs in the interleukin-1β and interleukin-6 genes were associated with basal CRP. No association was seen between CRP genotype and SLE. Using a variance components approach we estimated that the CRP genotype accounted for only 15% of the total genetic component of basal CRP variation, perhaps explaining the limited evidence of association between CRP and disease. Most of the genetic determinants of basal CRP variation therefore remain unknown. Multiple genes may be involved and identifying them will provide an insight into pathways regulating CRP expression, highlight potential cardiovascular disease and SLE candidates and improve the ability of basal CRP to predict cardiovascular risk.     

Association of Common CRP Gene Variants with CRP Levels and Cardiovascular Events

C‐reactive protein (CRP) is a well‐documented marker of atherosclerotic cardiovascular disease risk. We resequenced CRP to identify a comprehensive set of common SNP variants, then studied and replicated their association with baseline CRP level among apparently healthy subjects in the Women's Health Study (WHS; n = 717), Pravastatin Inflammation/CRP Evaluation trial (PRINCE; n = 1,110) and Physicians' Health Study (PHS; n = 509) cohorts. The minor alleles of four SNPs were consistently associated in all three cohorts with higher CRP, while the minor alleles of two SNPs were associated with lower CRP (p < 0.05 for each). Single marker and haplotype analysis in all three cohorts were consistent with functional roles for the 5′‐flanking triallelic SNP ?286C>T>A and the 3′‐UTR SNP 1846G>A. None of the SNPs associated with higher CRP were associated with risk of incident myocardial infarction (MI) or ischemic stroke in a prospective, nested case‐control study design from the PHS cohort (610 case‐control pairs). One SNP, ?717A>G, was unrelated to CRP levels but associated with decreased risk of MI (p = 0.001). Taken together, these data imply significant interactions between both genetic and environmental contributions to the increased CRP levels that predict a greater risk of future atherothrombotic events in epidemiological studies.     

Angiotensin-converting enzyme gene polymorphism in patients with systemic lupus

The renin-angiotensin-aldosterone system (RAAS) has been considered one of the probable pathophysiologic mechanisms involved in disease progression. Genetic polymorphism of the RAAS has been associated with the clinical course of renal disease. One of the genetic polymorphisms is a deletion or insertion of a 287 base pair fragment in intron 16 of the angiotensin-converting enzyme (ACE) gene. It is known that ACE gene polymorphism is present in humans and that it is associated with an increased risk of cardiovascular diseases, renal disease progression and sarcoidosis. In this study, the potential significance of ACE gene polymorphism in patients with systemic lupus erythematosus (SLE) was investigated. ACE gene polymorphism was determined in 18 patients with SLE and in 21 healthy volunteers as a control group. The mean age of patients was 38.5 years. All patients had a mean follow-up of 30.7 +/- 20.2 months (range 5-95 months). ACE genotypes were determined by the method of polymerase chain reaction. Proteinuria and creatinine were also followed. The frequency of DD, ID and II genotypes was 50%, 28% and 22% in SLE patients and 25%, 50% and 25% in healthy controls, respectively. DD genotype was more common in SLE patients than in the control group. The patients with II genotype had lower proteinuria and creatinine level than those with DD genotype (p < 0.05). The time to disease remission was shorter in patients with II genotype (p < 0.05). Study results indicated an increased frequency of D allele in SLE patients. The increased ACE activity in these patients pointed to the need of further studies of ACE gene polymorphism in SLE.     

系统性红斑狼疮遗传学研究进展

系统性红斑狼疮（systemic lupus erythematosus,SLE)通常被认为是自身免疫疾病的原型，遗传因素在疾病的发生中起重要作用。对狼疮鼠模型的研究已发现约30个基因位点与疾病产生有关，不同位点影响发病的不同环节。人类基因组研究则50个左右基因位点与SLE有关，其中1q23-24,1q41-42,2q37,4p16-15.2,6p21-11及16q13为6个显著相关区域，对特定患者，多个位点不同基因的组合可导致疾病表型的多样性。近期对候选基因的研究进一步证实，遗传因素在决定疾病易感性及临床表型时起作用，不同群体中所涉及的基因或其表达强度均有差异。     

Genetic determinants of basal C-reactive protein expression in Filipino systemic lupus erythematosus families

Basal C-reactive protein (CRP) is a heritable trait associated with long-term cardiovascular disease risk. Existing studies leave ambiguity over the key functional polymorphisms and fail to adjust for trans-acting effects. In a novel cohort of 285 Filipino systemic lupus erythematosus probands and their first-degree relatives, we quantified serum CRP and typed a dense map of CRP single-nucleotide polymorphisms (SNPs), along with SNPs in the interleukin-1 beta, interleukin-6 and apolipoprotein E genes. Ten CRP SNPs demonstrated association with basal CRP in a regression model (P=0.011-0.002). These delineated two haplotypes associated with high and low basal CRP expression (P=0.002). Differences in allele frequency were seen compared with Caucasian populations, enabling us to argue for an independent genetic effect from a phylogenetically distinct haplotype tagged by SNP rs1800947. We demonstrated an association between Apo epsilon 2 and higher basal CRP. Interleukin-6 genotype was associated with basal CRP, highlighting a role for acute-phase cytokines even in basal expression. Identifying these trans-acting variants may improve the use of basal CRP as a predictor cardiovascular risk, and increase our power to detect associations between CRP and disease.     

TRAF1/C5, eNOS, C1q, but not STAT4 and PTPN22 gene polymorphisms are associated with genetic susceptibility to systemic lupus erythematosus in Turkey

A significant source of variability in the literature on systemic lupus erythematosus (SLE) susceptibility genes has been the inability to replicate genetic findings across different racial or ethnic groups. We investigated whether a single nucleotide polymorphism (SNP) of the STAT4 (rs7574865), PTPN22 (rs2476601), TRAF1/C5 (rs10818488), and C1q (rs292001) genes as well as the 27-bp VNTR polymorphism on intron 4 of eNOS, previously associated with SLE in other populations, are also associated with SLE risk in Turkey. A group of 158 SLE patients and 155 healthy controls were included in this study. A genetic association of the TRAF1/C5, C1q, and eNOS gene polymorphism, but not of STAT4 and PTPN22, was found to confer a degree of risk for SLE. These data highlight the importance of comparative studies in different populations to confirm the previously detected genetic associations.     

The genetics of systemic lupus erythematosus: putting the pieces together

With lambda(s) estimates of 10 to 20 and other evidence of familial aggregation, as well as a monozygotic twin concordance rate >20, systemic lupus erythematosus (SLE) would appear to be a very promising phenotype using modern genetic approaches. Indeed, genetic associations are already known at numerous candidate loci including various HLA alleles, complement component genes, Fcgamma receptors, and others, and murine genetic studies of lupus models have provided additional candidate genes and potential syntenic linkages to evaluate in man. The completed genetic linkage studies performed on various collections of pedigrees multiplex for SLE have identified 60 susceptibility loci with varying degrees of evidence for linkage in man. Seven of these meet or exceed the threshold for significant linkage (LOD > or = 3.3 or P < or = 0.00005) at 1q22-23, 1q41, 2q37, 4p16, 6p21-11, 16q13 and 17p13. In addition, these linkages usually dominate in one ethnicity or another, suggesting that the responsible polymorphisms, once identified, will also vary by ethnicity. Evidence that these linkages can be reproduced range from outright independent confirmation (1q41, 4p16 and 6p21) to additional suggestive evidence in the genomic region of the purported linkage (1q22-23 and 2q37). The results now available suggest that human lupus genetics are robust and that gene identification should be possible using existing genetic approaches and technologies.     

Analysis of a GT microsatellite in the promoter of the foxp3/scurfin gene in autoimmune diseases

The aim of this study was to assess the possible association of the functional (GT)(n) microsatellite polymorphism in the FOXP3 gene with predisposition to several autoimmune diseases such as systemic lupus erythematosus (SLE), rheumatoid arthritis (RA), ulcerative colitis (UC), Crohn's disease, and celiac disease. We analyzed a case-control cohort composed of 231 SLE patients, 293 RA patients, 528 inflammatory bowel disease (354 Crohn's disease patients and 260 UC patients) patients, 103 celiac disease patients, and 274 healthy controls ethnically matched. Genotyping of (GT)(n) microsatellite was performed by polymerase chain reaction (PCR)-based method combined with fluorescent technology. We found no evidence for association of this polymorphism between controls and these autoimmune disease patients. Additionally, no differences in the genotype and allele distribution were found when patients were stratified according to clinical manifestation. The (GT)(n) microsatellite of the FOXP3 gene may not play a relevant role in the susceptibility to SLE, RA, inflammatory bowel disease, and celiac disease in our population.     

Epistatic Interaction between Genetic Variants in Susceptibility Gene ETS1 Correlates with IL‐17 Levels in SLE Patients

T‐helper cells that produce IL‐17 (Th17 cells) are a subset of CD4⁺ T‐cells with pathological roles in autoimmune diseases including systemic lupus erythematosus (SLE), and ETS1 is a negative regulator of Th17 cell differentiation. Our previous work on genome‐wide association study (GWAS) identified two variants in the ETS1 gene (rs10893872 and rs1128334) as being associated with SLE. However, like many other risk alleles for complex diseases, little is known on how these genetic variants might affect disease pathogenesis. In this study, we examined serum IL‐17 levels from 283 SLE cases and observed a significant correlation between risk variants in ETS1 and serum IL‐17 concentration in patients, which suggests a potential mechanistic link between these variants and the disease. Furthermore, we found that the two variants act synergistically in influencing IL‐17 production, with evidence of significant genetic interaction between them as well as higher correlation between the haplotype formed by the risk alleles and IL‐17 level in patient serum. In addition, the correlation between ETS1 variants and IL‐17 level seems to be more significant in SLE patients manifesting renal involvement, dsDNA autoantibody production or early‐onset.     

Polymorphisms of human CD19 gene: possible association with susceptibility to systemic lupus erythematosus in Japanese

CD19 regulates the signaling for B lymphocyte development, activation and proliferation. In mice, CD19 deficiency and overexpression were shown to result in hypogammaglobulinemia and autoantibody production, respectively. In the present study, we screened for the polymorphisms of CD19, and examined the detected polymorphisms for the association with rheumatoid arthritis (RA), Crohn's disease and systemic lupus erythematosus (SLE). Two SNPs, c.705G>T (P235P and IVS14-30C>T, were decreased (P = 0.0096 and P = 0.028, respectively), in SLE. A GT repeat polymorphism, c.*132(GT)(12-18), was detected within the 3'-untranslated region, and individuals with > or =15 times repeat was significantly increased in the independent two groups of Japanese SLE patients (P = 0.011 and P = 0.035, respectively); the overall difference between total SLE and controls was striking (P = 0.0061). No association was observed for RA and Crohn's disease. In addition, no variations other than the common polymorphisms were detected in four patients with common variable immunodeficiency, the phenotype of which resembles CD19 deficient mice. In Caucasian SLE families, this GT repeat polymorphism was rare. CD19 mRNA level in the isolated peripheral blood B lymphocytes was lower in individuals possessing (GT)(15-18) alleles compared with those without these alleles, both in controls and in SLE patients; however, the difference did not reach statistical significance. These results suggested that either the slight reduction in the CD19 mRNA level associated with the elongation of GT repeat, or an allele of another locus in linkage disequilibrium with CD19 (GT)(15-18), may be associated with susceptibility to SLE in Japanese.     

An osteopontin (SPP1) polymorphism is associated with systemic lupus erythematosus

Osteopontin (SPP1) is a soluble ligand with pleomorphic immunologic activities including activation of macrophage chemotaxis, promotion of Th1 responses, and activation of B1 B cells. It has been implicated in the development of murine lupus and is overexpressed in humans with systemic lupus erythematosus (SLE). We examined a polymorphism of osteopontin for an association with lupus in humans in an effort to determine whether there is any evidence that a genetic predisposition to altered osteopontin expression might explain the overexpression seen in human SLE patients. A silent polymorphism (707C>T, rs1126616) of osteopontin was significantly associated with SLE. Additional associations with renal disease and opportunisitic infections were suggested. This is the first phenotypic association with a polymorphic variant of osteopontin.     

Association between late-onset Alzheimer's disease and microsatellite polymorphisms in intron II of the human toll-like receptor 2 gene

The amyloid beta protein (Aβ) deposits in the brains of patients with Alzheimer's disease (AD) are closely associated with innate immune responses that were assumed to play a pivotal role in the pathogenesis of AD. Toll-like receptor 2 (TLR2) is thought to contribute to Aβ clearance. Studies have reported the presence and functional implications of guanine-thymine (GT) repeat microsatellite polymorphisms in intron II of the human TLR2 gene. The present study evaluated the association of the microsatellite polymorphism and sporadic late-onset AD (LOAD) in the Han Chinese population. The numbers of (GT) repeats were counted in 137 AD patients and in 137 non-AD control subjects, using polymerase chain reaction and genescan analysis. The alleles were divided into three subclasses: (GT)16 or less as the S allele, (GT)17 to (GT)22 as the M allele, and (GT)23 or more as the L allele. Patients with AD had more S alleles (P < 0.001; odds ratio (OR) = 2.32; 95% confidence interval (CI) = 1.57–3.42) and fewer L alleles (P = 0.02; OR = 0.66; 95% CI = 0.46–0.93) than did healthy controls. Genotypes SS and SM were more common, whereas ML and SL were less common in patients with AD. In subgroup analyses, the genotypes including S alleles were associated with an increased risk of LOAD (OR = 2.05, 95% CI = 1.26–3.34), and this association was influenced by the presence of APOE ?4 alleles. This study demonstrates an association of microsatellite polymorphisms in intron II of the human TLR2 gene with risk for LOAD in Han Chinese.     

Anti-C1q autoantibodies specific against the globular domain of the C1qB-chain from patient with lupus nephritis inhibit C1q binding to IgG and CRP

Lupus nephritis is one of the most severe manifestations of systemic lupus erythematosus. Higher titers of serum anti-C1q autoantibodies correlate with disease activity in patients with lupus nephritis. Anti-C1q autoantibodies have been shown to bind neo-epitopes within the collagen region of human C1q. In a preliminary study, we recently reported that the anti-C1q autoantibodies could also recognize epitopes within the globular domain (gC1q) of the C1q molecule. Here, 38 sera from patients with renal biopsy-proven lupus nephritis were screened for the presence of anti-gC1q autoantibodies, using recombinant globular head regions of individual A (ghA), B (ghB) and C (ghC) chains of human C1q. We isolated anti-gC1q autoantibodies from three selected patients. Human C1q was pre-incubated with increasing concentrations of the isolated anti-ghA, anti-ghB or anti-ghC autoantibodies and its binding to different C1q target molecules such as IgG and CRP was then evaluated. Anti-ghB, but not anti-ghA and anti-ghC autoantibodies, markedly inhibited C1q interaction with IgG as well as CRP. These results appear to suggest that the anti-ghB autoantibodies may partially induce acquired functional C1q deficiency and thus may interfere with the biological function of C1q.     

Association of osteopontin regulatory polymorphisms with systemic sclerosis

To test the involvement of osteopontin gene (OPN) in systemic sclerosis (SSc) susceptibility, two OPN single nucleotide polymorphisms previously reported to be associated with systemic lupus erythematosus, namely −156G/GG (proximal promoter) and +1239A/C (3′ untranslated region (UTR)), were tested in 357 Italian patients and 864 matched control subjects. OPN serum levels were determined by enzyme-linked immunosorbent assay in 32 patients and 116 controls. Compared with the controls, in SSc patients there was a significantly increased frequency of the alleles −156G (p = 0.0086), and +1239C (p = 0.00064), paralleling the association reported for systemic lupus erythematosus. According to logistic regression analysis, this association is primarily due to the effect of +1239 single nucleotide polymorphism. OPN serum levels were significantly higher in SSc patients than in controls (p = 0.00025). These data suggest that OPN genetic variations have a role in SSc susceptibility, reporting for the first time an involvement of this molecule in SSc pathogenesis and emphasizing that SSc shares pathogenetic mechanisms with other autoimmune diseases.