Association of polar amino acids at position 26 of the HLA-DQB1 first domain with the anticentromere autoantibody response in systemic sclerosis (scleroderma)

Association of HLA-DRB1*15:02:01, DQB1*05:01:24 and DPB1*13:01:01 in Thai patients with systemic sclerosis

INTRODUCTION

HLA studies in patients with systemic sclerosis (SSc) have shown variable results. This study aimed to examine the association of HLA class I and II risk alleles in Thai SSc patients, and clarify the contribution of risk HLA alleles to the pathogenesis and clinical manifestations.

METHODS

Blood samples from 92 SSc patients and 135 healthy controls (HCs) were collected. Eleven loci of the HLA class I (HLA-A, B, and C) and class II (HLA-DR, DP, and DQ) genes were determined by a 3-field (6-digit) analysis using the Next Generation DNA Sequencing (NGS) method. Anti-topoisomerase-I antibodies (ATA) and anti-centromere antibodies (ACA) were identified by ELISA methods.

RESULTS

Allele frequencies (AFs) of HLA-DRB1*15:02:01, DRB5*01:02:01, DQB1*05:01:24, DPB1*13:01:01, and DQA1*01:01:01 were increased significantly in the whole SSc and SSc patients with positive ATA, but with negative ACA (SSc/ATA+/ACA-). Of these, DPB1*13:01:01 was the most susceptible allele. The DRB1*15:02:01, DQB1:05:01:24, and DPB1*13:01:01 alleles were estimated to locate on the unique haplotype, and haplotype frequency was estimated to be significantly higher than those in the HCs (p=0.002). The linkage analysis of DRB1*15/16 revealed that most of the DRB1*15:02:01 alleles were linked to DRB5*01:02:01 or DRB5*01:08:01N. The linkage of DRB1*16:02:01 to DRB5*01:01:01 was observed frequently. The associations of risk alleles with several SSc clinical features were observed.

CONCLUSION

HLA-DRB1*15:02:01, DRB5*01:02:01, DQB1*05:01:24, and DPB1*13:01:01 on the unique haplotype were associated with the pathogenesis and clinical features of SSc in Thai patients. The linkage of DRB1*15:02:01 to DRB5*01:08:01N was observed commonly in northern Thai patients. This article is protected by copyright. All rights reserved.

Trans-ancestral fine-mapping of MHC reveals key amino acids associated with spontaneous clearance of hepatitis C in HLA-DQβ1

Spontaneous clearance of acute hepatitis C virus (HCV) infection is associated with single nucleotide polymorphisms (SNPs) on the MHC class II. We fine-mapped the MHC region in European (n = 1,600; 594 HCV clearance/1,006 HCV persistence) and African (n = 1,869; 340 HCV clearance/1,529 HCV persistence) ancestry individuals and evaluated HCV peptide binding affinity of classical alleles. In both populations, HLA-DQβ1Leu26 (p value_Meta = 1.24 × 10^-14) located in pocket 4 was negatively associated with HCV spontaneous clearance and HLA-DQβ1Pro55 (p value_Meta = 8.23 × 10^-11) located in the peptide binding region was positively associated, independently of HLA-DQβ1Leu26. These two amino acids are not in linkage disequilibrium (r² < 0.1) and explain the SNPs and classical allele associations represented by rs2647011, rs9274711, HLA-DQB1^∗03:01, and HLA-DRB1^∗01:01. Additionally, HCV persistence classical alleles tagged by HLA-DQβ1Leu26 had fewer HCV binding epitopes and lower predicted binding affinities compared to clearance alleles (geometric mean of combined IC₅₀ nM of persistence versus clearance; 2,321 nM versus 761.7 nM, p value = 1.35 × 10^-38). In summary, MHC class II fine-mapping revealed key amino acids in HLA-DQβ1 explaining allelic and SNP associations with HCV outcomes. This mechanistic advance in understanding of natural recovery and immunogenetics of HCV might set the stage for much needed enhancement and design of vaccine to promote spontaneous clearance of HCV infection.

Associations of GWAS-Identified Risk Loci with Progression, Efficacy and Toxicity of Radiotherapy of Head and Neck Squamous Cell Carcinoma Treated with Radiotherapy

Background

Head and neck squamous cell carcinoma (HNSCC) ranks the sixth most common cancer worldwide. This study aims to evaluate the associations of GWAS-identified HNSCC risk loci with progression, efficacy and toxicity of radiotherapy of HNSCC treated with radiotherapy.

Methods

Six GWAS-identified risk loci were genotyped and evaluated. Multivariate logistic regression was used to determine the associations of these SNPs with progression, efficacy and toxicity of radiotherapy of HNSCC treated with radiotherapy.

Results

We found that rs259919 was significantly associated with higher TNM stage (allele A vs G: OR=1.49; 95% CI: 1.09–2.03; P=0.012), while rs3135001 was significantly associated with better efficacy of radiotherapy (allele T vs C: OR=1.80, 95% CIs=1.19–2.73, P=0.005). Both SNP rs1265081 (allele A vs C: OR=1.41, 95% CIs=1.08–1.86, P=0.012) and rs3135001 (allele T vs allele C: OR=0.53, 95% CIs=0.35–0.79, P=0.002) were significantly associated with the occurrence of grade 3–4 oral mucositis.

Conclusion

We identified that three GWAS-identified HNSCC risk loci were significantly associated with progression, efficacy and toxicity of radiotherapy of HNSCC. Our findings strengthen the understanding of the essential role of genetic background in the progression and therapeutic effects of HNSCC.

Clinical and Molecular Features of Anti-CENP-B Autoantibodies

Centromeric proteins are the foundation for assembling the kinetochore, a macromolecular complex that is essential for accurate chromosome segregation during mitosis. Anti-centromere antibodies (ACAs) are polyclonal autoantibodies targeting centromeric proteins (CENP-A, CENP-B, CENP-C), predominantly CENP-B, and are highly associated with rheumatologic disease (lcSSc/CREST syndrome). CENP-B autoantibodies have also been reported in cancer patients without symptoms of rheumatologic disease. The rise of oncoimmunotherapy stimulates inquiry into how and why anti-CENP-B autoantibodies are formed. In this review, we describe the clinical correlations between anti-CENP-B autoantibodies, rheumatologic disease, and cancer; the molecular features of CENP-B; possible explanations for autoantigenicity; and, finally, a possible mechanism for induction of autoantibody formation.

Genomic and genetic studies of systemic sclerosis: A systematic review

Systemic sclerosis is an autoimmune rheumatic disease characterised by fibrosis, vasculopathy and inflammation. The exact aetiology of SSc remains unknown but evidences show that various genetic factors may be involved. This review aimed to assess HLA alleles/non-HLA polymorphisms, microsatellites and chromosomal abnormalities that have thus far been associated with SSc. PubMed, Embase and Scopus databases were searched up to July 29, 2015 using a combination of search-terms. Articles retrieved were evaluated based on set exclusion and inclusion criteria. A total of 150 publications passed the filters. HLA and non-HLA studies showed that particular alleles in the HLA-DRB1, HLA-DQB1, HLA-DQA1, HLA-DPB1 genes and variants in STAT4, IRF5 and CD247 are frequently associated with SSc. Non-HLA genes analysis was performed using the PANTHER and STRING₁₀ databases. PANTHER classification revealed that inflammation mediated by chemokine and cytokine, interleukin and integrin signalling pathways are among the common extracted pathways associated with SSc. STRING₁₀ analysis showed that NFKB1, CSF3R, STAT4, IFNG, PRL and ILs are the main "hubs" of interaction network of the non-HLA genes associated with SSc. This study gathers data of valid genetic factors associated with SSc and discusses the possible interactions of implicated molecules.

Angiotensin II Type 1 receptor (AGTR1) gene polymorphisms are associated with vascular manifestations in patients with systemic sclerosis (SSc)

INTRODUCTION

Systemic sclerosis (SSc) shows variable clinical expression in different ethnic groups; vascular abnormalities are a prominent feature of this disease and its clinical expression may be influenced by genetic factors.

PATIENTS AND METHODS

Herein, we describe 15 polymorphisms of the renin-angiotensin-aldosterone pathway in 170 Mexican admixed SSc patients (defined as patients with Mexican ancestry for at least 3 generations) and 199 healthy controls. We determined the presence of angiotensin II Type 1 receptor (AGTR1), angiotensin converting enzyme (ACE) and Endothelin 1 single nucleotide polymorphisms (SNPs) using 5' exonuclease TaqMan genotyping assays on a 7900HT real-time fast polymerase chain reaction (PCR) system.

RESULTS

These polymorphisms had a similar distribution between SSc patients and controls, but we found that the AGTR1 G-680T (rs275652) (p = 0.02; OR 3.5; 95%CI 1.2-10.4) and AGTR1 A-119G (rs275653) (p = 0.008; OR 4.2; 95% CI 1.5-12.1) polymorphisms were associated with severe vascular involvement in our SSc patients.

CONCLUSIONS

This is the first report of the association of these polymorphisms with vasculopathy in Mexican admixed SSc patients. Our findings suggested that the angiotensin II Type 1 receptor genotype may influence the clinical expression of vasculopathy in these patients. Functional analyses should follow.

Current perspectives on the immunopathogenesis of systemic sclerosis

Systemic sclerosis (SSc or scleroderma) is a progressive and highly debilitating autoimmune disorder characterized by inflammation, vasculopathy, and extensive fibrosis. SSc is highly heterogeneous in its clinical presentation, extent and severity of skin and internal organ involvement, and clinical course and has the highest fatality rate among connective tissue diseases. While clinical outcomes have improved in recent years, no current therapy is able to reverse or slow the natural progression of SSc, a reflection of its complex pathogenesis. Although activation of the immune system has long been recognized, the mechanisms responsible for the initiation of autoimmunity and the role of immune effector pathways in the pathogenesis of SSc remain incompletely understood. This review summarizes recent progress in disease pathogenesis with particular focus on the immunopathogenetic mechanisms of SSc.

HLA Class I and II Blocks Are Associated to Susceptibility, Clinical Subtypes and Autoantibodies in Mexican Systemic Sclerosis (SSc) Patients

INTRODUCTION

Human leukocyte antigen (HLA) polymorphism studies in Systemic Sclerosis (SSc) have yielded variable results. These studies need to consider the genetic admixture of the studied population. Here we used our previously reported definition of genetic admixture of Mexicans using HLA class I and II DNA blocks to map genetic susceptibility to develop SSc and its complications.

METHODS

We included 159 patients from a cohort of Mexican Mestizo SSc patients. We performed clinical evaluation, obtained SSc-associated antibodies, and determined HLA class I and class II alleles using sequence-based, high-resolution techniques to evaluate the contribution of these genes to SSc susceptibility, their correlation with the clinical and autoantibody profile and the prevalence of Amerindian, Caucasian and African alleles, blocks and haplotypes in this population.

RESULTS

Our study revealed that class I block HLA-C*12:03-B*18:01 was important to map susceptibility to diffuse cutaneous (dc) SSc, HLA-C*07:01-B*08:01 block to map the susceptibility role of HLA-B*08:01 to develop SSc, and the C*07:02-B*39:05 and C*07:02-B*39:06 blocks to map the protective role of C*07:02 in SSc. We also confirmed previous associations of HLA-DRB1*11:04 and -DRB1*01 to susceptibility to develop SSc. Importantly, we mapped the protective role of DQB1*03:01 using three Amerindian blocks. We also found a significant association for the presence of anti-Topoisomerase I antibody with HLA-DQB1*04:02, present in an Amerindian block (DRB1*08:02-DQB1*04:02), and we found several alleles associated to internal organ damage. The admixture estimations revealed a lower proportion of the Amerindian genetic component among SSc patients.

CONCLUSION

This is the first report of the diversity of HLA class I and II alleles and haplotypes Mexican patients with SSc. Our findings suggest that HLA class I and class II genes contribute to the protection and susceptibility to develop SSc and its different clinical presentations as well as different autoantibody profiles in Mexicans.

Systemic Sclerosis is a Complex Disease Associated Mainly with Immune Regulatory and Inflammatory Genes

Systemic sclerosis (SSc) is a fibrotic and autoimmune disease characterized clinically by skin and internal organ fibrosis and vascular damage, and serologically by the presence of circulating autoantibodies. Although etiopathogenesis is not yet well understood, the results of numerous genetic association studies support genetic contributions as an important factor to SSc. In this paper, the major genes of SSc are reviewed. The most recent genome-wide association studies (GWAS) are taken into account along with robust candidate gene studies. The literature search was performed on genetic association studies of SSc in PubMed between January 2000 and March 2014 while eligible studies generally had over 600 total participants with replication. A few genetic association studies with related functional changes in SSc patients were also included. A total of forty seven genes or specific genetic regions were reported to be associated with SSc, although some are controversial. These genes include HLA genes, STAT4, CD247, TBX21, PTPN22, TNFSF4, IL23R, IL2RA, IL-21, SCHIP1/IL12A, CD226, BANK1, C8orf13-BLK, PLD4, TLR-2, NLRP1, ATG5, IRF5, IRF8, TNFAIP3, IRAK1, NFKB1, TNIP1, FAS, MIF, HGF, OPN, IL-6, CXCL8, CCR6, CTGF, ITGAM, CAV1, MECP2, SOX5, JAZF1, DNASEIL3, XRCC1, XRCC4, PXK, CSK, GRB10, NOTCH4, RHOB, KIAA0319, PSD3 and PSOR1C1. These genes encode proteins mainly involved in immune regulation and inflammation, and some of them function in transcription, kinase activity, DNA cleavage and repair. The discovery of various SSc-associated genes is important in understanding the genetics of SSc and potential pathogenesis that contribute to the development of this disease.

HLA markers for poor prognosis in systemic sclerosis Brazilian patients

Objectives. The aim of this study was to evaluate human leukocyte antigen (HLA) involvement in the disease expression and poor prognostic clinical features (pulmonary fibrosis and pulmonary arterial hypertension) in patients diagnosed with systemic sclerosis (SSc) in a multiethnic population. Methods. SSc patients followed up between 2008 and 2011 were included, and clinical data were obtained through records review. Molecular HLA typing was performed (polymerase chain reaction amplification technique using specific primer sequences). The statistical analysis involved Fisher's exact test and Pearson's corrected chi-square test. P  values ≤ 0.05 were considered significant. The delta method was used to estimate the variance of the prevalence ratio (PR). Results. A total of 141 patients (120 women and 21 men) with SSc were studied, including 33.3% with diffuse cutaneous SSc (dcSSc), 62.4% with limited cutaneous SSc (lcSSc), and 4.3% with sine scleroderma. Pulmonary fibrosis was present in 61 patients (43.3%), and the HLA-A∗30 and DQB1∗04 alleles were related to susceptibility. In contrast, the HLA-DRB1∗01 and DQB1∗05 alleles were protective. Pulmonary arterial hypertension was diagnosed in 19 patients (13.5%) and was associated with HLA-B∗35 and C∗04; in contrast, C∗03 seemed to be protective. Conclusions. Our current study documents the association of some classes I and II HLA alleles with the most severe clinical manifestations in a multiethnic case series. Our findings differed slightly from the previous data in other populations.

Autoantibodies recognizing the amino terminal 1-17 segment of CENP-A display unique specificities in systemic sclerosis

Centromere-associated protein A (CENP-A), a common autoimmune target in a subset of systemic sclerosis patients, appears to have no role to explain why its corresponding auto-antibodies are more frequently found in the limited than the diffuse form of systemic sclerosis. Therefore, we investigated the fine specificity of anti-CENP-A antibodies as a first step to understanding their role in systemic sclerosis pathology. We focused on the amino-terminal portion of CENP-A spanning amino acids 1 to 17 (Ap(1-17)), which represents, along with Ap(17-30), an immunodominant epitope of the protein. Peptide Ap(1-17) was used to purify antibodies from 8 patients with systemic sclerosis. Anti-Ap(1-17) antibodies specifically reacted with human CENP-A but did not cross-react with CENP-B or Ap(17-30). Panning of a phage display peptide library with anti-Ap(1-17) antibodies from 2 patients identified two novel, partially overlapping motifs, <(5)Rx(st)xKP(10)> and <(9)KPxxPxR(15)> as the result of the alignment of specific phage clone insert sequences. Anti-Ap(1-17) IgG from the 8 patients had different reactivities to isolated phage clone insert sequences. Scanning the Swiss-Prot database revealed a large number of different types of proteins containing the two Ap(1-17) antigenic motifs. These data show that anti-CENP-A(1-17) antibodies are generated independently from anti-CENP-B antibodies and display great heterogeneity in their specificity by recognizing different motifs within that peptide sequence. This finding, along with the widespread interspecies and human tissue distribution of the two motifs, suggests that the number of motif-expressing proteins which can be the potential target of these antibodies is markedly higher than that estimated from the peptide-based epitope spreading model.

Epidemiology of systemic sclerosis

Systemic sclerosis (SSc) is a multisystem auto-immune disease. The two main subtypes of SSc (limited and diffuse) typically have differing courses and prognoses. New classification criteria have been proposed to identify SSc in the earliest stages, before skin involvement. Over the past three decades, there has been an apparent increase in the incidence of SSc to approximately 20 per million, possibly due to improved diagnosis. The most extensively studied environmental associations of SSc are organic solvents and silica but no single risk factor has emerged. Recent genetic studies have identified new susceptibility factors including human leucocyte antigen (HLA) haplotypes and polymorphisms in immune regulatory genes. Despite earlier disease recognition and effective treatment for some of its complications, SSc still carries a high mortality, particularly due to cardiorespiratory complications. Although some predictors of organ involvement and outcomes have been identified, novel biomarkers are greatly needed. Due to low disease prevalence, large multicentre research collaborations are required.

Analysis of HLA-DRB1 polymorphisms in Japanese patients with primary biliary cirrhosis (PBC): The HLA-DRB1polymorphism determines the relative risk of antinuclear antibodies for disease progression in PBC

AIMS

Anti-gp210 and anti-centromere antibodies are different risk factors for the progression of primary biliary cirrhosis (PBC). However, the association of human leukocyte antigen (HLA) polymorphisms with these risk factors is unknown.

METHODS

We determined the HLA-DRB1 genotype in 334 Japanese PBC patients and studied their serum antibodies to gp210 and centromere during the 1-452-month observation period.

RESULTS

Anti-gp210 (odds ratio [OR] 46.56, 95% confidence interval [CI], 9.20-850.1) and anti-centromere antibodies (OR, 2.36, 95% CI, 1.28-4.35) were significant risk factors for jaundice- and nonjaundice-type progression, respectively. HLA-DRB1*0405 and *0803 predisposed patients to anti-gp210 (OR, 1.61, 95% CI, 1.08-2.39) and anti-centromere (OR, 2.30, 95% CI, 1.41-3.73) antibody production, respectively. HLA-DRB1*1502 and *0901 patients were predisposed to nonjaundice-type progression (OR, 1.98, 95% CI, 1.13-3.40 and OR, 1.78, 95% CI, 1.02-3.03), while HLA-DRB1*0803 and *0405 patients were predisposed to disease development (OR, 2.24, 95% CI, 1.48-3.41 and OR, 1.53, 95% CI, 1.11-2.11, respectively). Stratifying patients by HLA-DRB1 alleles revealed that anti-gp210 antibodies was a strong risk factor, regardless of the HLA-DRB1 alleles for jaundice-type progression, while anti-centromere antibodies was a significant risk factor for nonjaundice-type progression in patients with HLA-DRB1*0405 (OR, 6.89, 95% CI, 2.18-26.56) and -DRB1*0803 (OR, 5.42, 95% CI, 1.47-24.62) but not other HLA-DRB1 alleles.

CONCLUSIONS

HLA-DRB1 polymorphisms are significantly associated with not only disease development and progression but also antinuclear antibody production and the determination of the relative risk of antinuclear antibodies that contribute to PBC disease progression.

Novel sequence feature variant type analysis of the HLA genetic association in systemic sclerosis

We describe a novel approach to genetic association analyses with proteins sub-divided into biologically relevant smaller sequence features (SFs), and their variant types (VTs). SFVT analyses are particularly informative for study of highly polymorphic proteins such as the human leukocyte antigen (HLA), given the nature of its genetic variation: the high level of polymorphism, the pattern of amino acid variability, and that most HLA variation occurs at functionally important sites, as well as its known role in organ transplant rejection, autoimmune disease development and response to infection. Further, combinations of variable amino acid sites shared by several HLA alleles (shared epitopes) are most likely better descriptors of the actual causative genetic variants. In a cohort of systemic sclerosis patients/controls, SFVT analysis shows that a combination of SFs implicating specific amino acid residues in peptide binding pockets 4 and 7 of HLA-DRB1 explains much of the molecular determinant of risk.

Major histocompatibility complex (MHC) class II alleles, haplotypes and epitopes which confer susceptibility or protection in systemic sclerosis: analyses in 1300 Caucasian, African-American and Hispanic cases and 1000 controls

Objective

To determine human leucocyte antigen-class II (HLA-class II) (DRB1, DQB1, DQA1 and DPB1) alleles, haplotypes and shared epitopes associated with scleroderma (systemic sclerosis (SSc)) and its subphenotypes in a large multi-ethnic US cohort by a case–control association study.

Patients and methods

1300 SSc cases (961 white, 178 black and 161 Hispanic subjects) characterised for clinical skin forms (limited vs diffuse), SSc-specific autoantibodies (anticentromere (ACA), anti-topoisomerase I (ATA), anti-RNA polymerase III (ARA), anti-U3 ribonucleoprotein (fibrillarin)) and others were studied using molecular genotyping. Statistical analyses in SSc itself by ethnicity, gender, skin type and autoantibodies were performed using exact logistic regression modelling for dominant, additive and recessive effects from HLA.

Results

The strongest positive class II associations with SSc in white and Hispanic subjects were the DRB1*1104, DQA1*0501, DQB1*0301 haplotype and DQB1 alleles encoding a non-leucine residue at position 26 (DQB1 26 epi), while the DRB1*0701, DQA1*0201, DQB1*0202 haplotype and DRB1*1501 haplotype were negatively correlated and possibly protective in dominant and recessive models, respectively. These associations did not discriminate between limited and diffuse SSc. SSc in black subjects was associated with DRB1*0804, DQA1*0501, DQB1*0301 alleles. DPB1*1301 showed the highest odds ratio for ATA (OR = 14). Moreover, it showed no linkage disequilibrium or gene interaction with DR/DQ. ACA was best explained by DQB1*0501 and DQB1*26 epi alleles and ARA by DRB1*0404, DRB1*11 and DQB1*03 alleles in white and Hispanic subjects but DRB1*08 in black subjects.

Conclusion

These data indicate unique and multiple HLA-class II effects in SSc, especially on autoantibody markers of different subphenotypes.

Association of IL-10 receptor 2 (IL10RB) SNP with systemic sclerosis

Interleukin-10 (IL-10) signaling has been suggested to play a role in systemic sclerosis (SSc). IL10RB codes for IL-10 receptor 2 (IL-10R2), a component shared in receptor complexes for IL-10, IL-22, IL-26 and interferon (IFN)-lambda. In this study, we examined association of IL10RB polymorphism with susceptibility to SSc. Genotype A/A at rs2834167 (47K/K) was significantly increased in diffuse cutaneous SSc (dcSSc) (41.3% in dcSSc, 20.9% in controls, P=0.0018, odds ratio=2.67). A SNP in the 5' flanking region of IL10RB, rs999788, also showed association with dcSSc; however, this association was shown to be secondarily caused by linkage disequilibrium with rs2834167. Significant association was not observed in limited cutaneous SSc (lcSSc). Presence of anti-topoisomerase I antibody was also associated with rs2834167A/A genotype (P=0.0019). Serum IL-10 level was significantly associated with the number of rs2834167A allele (P=0.007). These findings suggested that signaling through IL-10R2 may play a causative role in dcSSc.

[Etiopathogenesis. New concepts]

Systemic sclerosis is a complex, progressive autoimmune disease. The origin is, so far, unknown and it is characterized by immunological and endothelial damage followed by fibrosis. Interaction between the host genetic backgrounds with environmental factors is thought to turn out an abnormal immune response characterized by clonal expansion of Th2 repertoire, upregulation of pro-fibrotic cytokines and dysregulated B cells. Specific autoantibodies profiles are associated with clinical subtypes of the diseases. Endothelial activation is an early feature with damage of the vasocontrictive and vasodilation response. Finally, persistent tissue ischemia and abnormal immune response produce myofibroblast proliferation andoverproduction of extracellular matrix proteins and fibrosis.

Systemic and localized scleroderma

Sclerosing conditions of the skin are manifested by a full spectrum of presentations that includes skin-limited forms as well as those which can involve internal organs and result in death. At this point, we are just beginning to understand the mechanisms of tissue fibrosis, and it is likely that the fibrotic processes are a heterogeneous group of disorders in which perturbation of multiple molecular pathways, including vascular and immunologically mediated pathways, can lead to fibrosis. We now have some moderately effective therapies for vascular aspects of systemic sclerosis (eg, bosentan for pulmonary arterial hypertension, calcium-channel blockers for Raynaud's, or angiotensin-converting enzyme inhibitors for renal crisis). We also are beginning to find treatments interrupting the immunologic pathways that manifest as systemic sclerosis (eg, methotrexate for the skin or cyclophosphamide for the lungs). The basic process of fibrosis, however, awaits proven, effective therapy.

Systemic sclerosis: hypothesis-driven treatment strategies

We review data from controlled trials and randomised controlled trials to examine the hypothesis for the pathogenesis of systemic sclerosis. Strategies used to treat the vascular complications in systemic sclerosis have so far shown the biggest successes, especially in the management of renal crisis and pulmonary arterial hypertension. Because these drugs have improved function and quality of life and have increased survival rates, they can truly be classified as disease-modifying compounds. Immunosuppressive therapy with cyclophosphamide in particular has also shown evidence of efficacy, and randomised controlled trials of autologous stem-cell transplantation are underway. So far, strategies to reduce or control fibrosis directly (bosentan, interferon gamma, and relaxin) have been disappointing but new strategies against fibrosis based on advanced understanding of the molecular biology of systemic sclerosis hold promise. Treatments against several cardinal features of the disorder simultaneously have not yet been examined but are being considered for future trials.

Association of TAP1 and TAP2 Gene Polymorphisms With Systemic Sclerosis in Korean Patients

We sought to determine whether transporter associated with antigen processing (TAP) gene polymorphism is associated with susceptibility to systemic sclerosis (SSc). TAP1 and TAP2 gene polymorphisms were analyzed in 61 Korean patients with SSc and 100 ethnically matched healthy Koreans by polymerase chain reaction-restriction fragment length polymorphism. Human leukocyte antigen (HLA)-DRB1 genotyping data of the patients from our previous study was used for the assessment of independent role of TAP genes to SSc susceptibility. Patients were stratified according to anti-topoisomerase I (anti-topo I) antibody status and clinical subsets of diffuse and limited cutaneous SSc (dcSSc and lcSSc). TAP1 and TAP2 gene polymorphisms were associated with different subsets of SSc: TAP1*A/A genotype with anti-topo I-positive dcSSc (p = 0.01, p corrected = 0.04), TAP2*A1/C genotype with anti-topo I-positive lcSSc (p < 0.05), TAP2*Bky2 and *C alleles with anti-topo I-negative dcSSc (both p < 0.05), and TAP2*B/E genotype with anti-topo I-negative lcSSc (p = 0.004). Although TAP gene associations were generally weak, some associations (TAP2*A1/C, TAP2*C, and TAP2*B/E) with different subsets of SSc were independent of HLA-DR associations, revealing even stronger associations (TAP2*A1/C and TAP2*C) among individuals not possessing the risk HLA-DR alleles. These results suggest the possible role of TAP gene polymorphisms in the genetic susceptibility to SSc.

Analysis of systemic sclerosis in twins reveals low concordance for disease and high concordance for the presence of antinuclear antibodies

OBJECTIVE

To examine concordance for systemic sclerosis (SSc) in monozygotic (MZ) and dizygotic (DZ) twins.

METHODS

MZ and DZ twins were recruited nationwide. Zygosity was confirmed by DNA fingerprint analysis. The presence of antinuclear antibodies (ANAs) was determined using indirect immunofluorescence with HEp-2 cells as substrate. Identification of SSc-associated serum autoantibodies was performed by immunoprecipitation and double immunodiffusion. Major histocompatibility complex class II alleles were identified by polymerase chain reaction-restriction fragment length polymorphism analysis.

RESULTS

Concordance for SSc was found to be similar in MZ and DZ twins. Overall concordance for SSc was low in the twins (4.7%). Concordance for the presence of ANAs was significantly higher in MZ twins compared with DZ twins. SSc-associated serum autoantibodies occurred exclusively in patients with SSc. The distribution of SSc-associated serum autoantibodies was similar to that observed in our large database of SSc patients. Increased HLA allele sharing was detected in DZ twins, irrespective of disease concordance.

CONCLUSION

These results indicate that inherited genetic factors are not sufficient to explain the development of SSc. Rather, these data indicate that inheritance may play a role in the development of serum autoantibodies in the "healthy" twin sibling of an SSc patient.

Coexistence of antitopoisomerase I and anticentromere antibodies in patients with systemic sclerosis

BACKGROUND

Antibodies targeting DNA topoisomerase I (ATA) or centromere proteins (ACA) are associated with clinical subsets of patients with systemic sclerosis (SSc). The occurrence of those autoantibodies is considered to be mutually exclusive.

OBJECTIVE

To describe the clinical and immunogenetic data of three patients who are co-expressing both antibodies, and then review previous publications.

METHODS

Both antibodies were detected by different methods, including indirect immunofluorescence technique, enzyme linked immunosorbent assay, immunodiffusion, and immunoblot. Patients were HLA typed by serological and molecular genetic methods. Data were extracted from published reports for comparison. The search for published studies was through Medline and other database research programmes.

RESULTS

During routine laboratory diagnostics over several years three patients with scleroderma and coincidence of ATA and ACA were identified: patient 1 with diffuse SSc, Raynaud's phenomenon, puffy fingers and fingertip necrosis, contractures, and calcinosis; patient 2 with diffuse SSc, Raynaud's phenomenon, oedema of the hands, and interstitial calcinosis of hands, knees, and shoulders, and pulmonary fibrosis; patient 3 with scleroderma of hands, forearms, and face, Raynaud's phenomenon, puffy fingers, finger contractures, fingertip necrosis, and calcinosis. All three patients studied were carriers of HLA alleles known to be associated with these autoantibodies. In serial measurements the concentrations of the two antibodies showed independent or even reverse fluctuations. Screening of 100 patients with ACA for ATA and vice versa disclosed no further patients with coincidence of these antibodies. Twenty eight cases of ACA/ATA coexistence in 5423 patients (0.52%) with SSc or SSc associated symptoms were found in an analysis of published studies.

CONCLUSION

The expression of ATA and ACA is not totally mutually exclusive, but coincidence is rare (<1% of patients with SSc). Patients with both autoantibodies often have diffuse scleroderma and show immunogenetic features of both antibody defined subsets of SSc.

Systemic sclerosis in 3 US ethnic groups: a comparison of clinical, sociodemographic, serologic, and immunogenetic determinants

OBJECTIVE

To determine whether ethnic factors influence the presentation, serologic expression and immunogenetics of systemic sclerosis (SSc), patients from 3 ethnic groups were compared for clinical features, SSc-associated autoantibodies, and human leukocyte antigen (HLA) class II alleles.

METHODS

Fifty-four Hispanics, 28 African Americans, and 79 whites from Texas with recent-onset (less than 5 years) SSc enrolled in a prospective longitudinal study were assessed for sociodemographic, clinical, immunologic, immunogenetic, behavioral, and psychologic parameters using validated instruments and standard laboratory techniques. Serologic and immunogenetic characteristics from these patients and larger retrospective SSc cohorts of the same ethnic groups also were examined.

RESULTS

Hispanics and African Americans in the prospective cohort were more likely to have diffuse skin involvement, skin pigmentary changes, digital ulcers, pulmonary hypertension (African Americans), and an overall lower sociodemographic status than whites, who had more facial telangiectasia and hypothyroidism. In the larger combined prospective and retrospective groups of SSc patients, whites were likely to have more anticentromere antibodies (ACA) and African Americans more anti-U1-ribonucleoprotein (RNP) and anti-U3-RNP (fibrillarin) autoantibodies. HLA-DQB1*0301 was significantly associated with SSc per se in all 3 ethnic groups; HLA-DRB1*11 correlated with the anti-topoisomerase I antibody response, and HLA-DRB1*01, DRB1*04, and DQB1*0501 with ACA.

CONCLUSIONS

Important sociodemographic, clinical, and serologic differences exist between whites, African Americans, and Hispanics, despite shared genetic (HLA class II) predisposing factors. The impact of these differences on prognosis remain to be determined.

Genetic factors in the etiology of systemic sclerosis and Raynaud phenomenon

There is increasing evidence that genetic factors play important roles in susceptibility to and expression of systemic sclerosis (SSc), as well as primary Raynaud phenomenon. Familial aggregation for SSc, although infrequent (1.2%-1.5% of SSc families), has now been established, and when compared with population prevalence represents a significant risk factor for the disease and lays a firmer foundation for genetics in etiopathogenesis. Major histocompatibility complex class II alleles increase disease risk in some populations but are more strongly correlated with specific autoantibody profiles. Microchimerism influenced by human leukocyte antigen also remains an intriguing hypothesis. A variety of extracellular matrix genes, including fibrillin-1, have become additional candidates for contributing to what is likely a complex genetic disease. Reviewed here is evidence relating to these concepts, especially new data reported over the last year.

Autoantibodies to the Extracellular Matrix Microfibrillar Protein, Fibrillin-1, in Patients with Scleroderma and Other Connective Tissue Diseases

A duplication in the fibrillin-1 gene has been implicated as the cause of the tight skin 1 (tsk1) phenotype, an animal model of scleroderma or systemic sclerosis (SSc). In addition to the production of abnormal fibrillin-1 protein, the tsk1 mouse also produces autoantibodies to fibrillin-1. Among a population of Choctaw Native Americans with the highest prevalence of SSc yet described, a chromosome 15q haplotype containing the fibrillin-1 gene has been strongly associated with SSc. With a recombinant human fibrillin-1 protein, autoantibodies to fibrillin-1 were detected in the sera of Native American SSc patients that correlated significantly with disease. Abs to fibrillin-1 also were detected in sera from Japanese, Caucasian, and African-American SSc patients. Compared with other ethnic groups, Japanese and Native American SSc patients had significantly higher frequencies of anti-fibrillin-1 Abs. Sera from patients with diffuse SSc, calcinosis, Raynaud’s, esophageal dysmotility, sclerodactyly, and telangiectasias syndrome and mixed connective tissue disease also had significantly higher frequencies of anti-fibrillin-1 Abs than sera from controls or patients with other non-SSc connective tissue diseases (lupus, rheumatoid arthritis, and Sjögren’s syndrome). Ab specificity for fibrillin-1 was demonstrated by the lack of binding to a panel of other purified autoantigens. The results presented demonstrate for the first time the presence of high levels of anti-fibrillin-1 Abs in a significant portion of patients with SSc.

HLA haplotypes and microsatellite polymorphisms in and around the major histocompatibility complex region in a Native American population with a high prevalence of scleroderma (systemic sclerosis)

Choctaw Native Americans in southeastern Oklahoma have the highest prevalence of scleroderma or systemic sclerosis yet found (469/100,000). An Amerindian HLA DR2 haplotype (DRB1*1602) was significantly associated with scleroderma in this population in a previous study. It is not known, however, if other disease genes are linked to this HLA haplotype. The regions flanking the HLA loci were studied with polymorphic microsatellite markers. An extended HLA DR2 (DRB1*1602, DQA1*0501, DQB1*0301, DPB1*1301) haplotype that includes the class I and III regions was identified which was significantly associated with scleroderma in the Oklahoma Choctaw. No other significant associations with microsatellite marker alleles immediately flanking the HLA region were found.

Association of microsatellite markers near the fibrillin 1 gene on human chromosome 15q with scleroderma in a Native American population

OBJECTIVE

To localize disease genes for scleroderma, or systemic sclerosis (SSc), in a population of Choctaw Native Americans with a high prevalence of SSc, in which there is evidence of a possible founder effect.

METHODS

A candidate gene approach was used in which microsatellite alleles on human chromosomes 15q and 2q, homologous to the murine tight skin 1 (tsk1) and tsk2 loci, respectively, were analyzed in Choctaw SSc cases and race-matched normal controls for possible disease association. Genotyping first-degree relatives of the cases identified potential disease haplotypes, and haplotype frequencies were obtained by expectation-maximization and maximum-likelihood estimation methods. Simultaneously, the ancestral origins of contemporary Choctaw SSc cases were ascertained using census and historical records.

RESULTS

A multilocus 2-cM haplotype was identified on human chromosome 15q homologous to the murine tsk1 region, which showed a significantly increased frequency in SSc cases compared with controls. This haplotype contains 2 intragenic markers for the fibrillin 1 (FBN1) gene. Genealogical studies demonstrated that the SSc cases were distantly related, and their ancestry could be traced back to 5 founding families in the mid-eighteenth century. The probability that the SSc cases share this haplotype due to familial aggregation effects alone was calculated and found to be very low. There was no evidence of any microsatellite allele disturbances on chromosome 2q in the region homologous to the tsk2 locus or the region containing the interleukin-1 family.

CONCLUSION

A 2-cM haplotype on chromosome 15q that contains FBN1 is associated with scleroderma in Choctaw Native Americans from Oklahoma. This haplotype may have been inherited from common founders about 10 generations ago and may contribute to the high prevalence of SSc that is now seen.

Alopecia areata and cytomegalovirus infection in twins: genes versus environment?

BACKGROUND

Alopecia areata (AA) is hypothesized to be an organ-specific autoimmune disease mediated by T cells directed to the hair follicle. Genetic susceptibility may be conferred by HLA, and an environmental trigger, such as a viral infection, is suspected. The incidence of AA in the population is estimated to be 1.7%, with an average of one in four patients having a positive family history.

OBJECTIVE

Our purpose was to examine the concordance rate of AA among identical versus fraternal twins and the correlation between stress, cytomegalovirus (CMV) infection, and disease.

METHODS

Families with AA were solicited from dermatologists in the United States and through a Website on the Internet. HLA class 2 typing and identification of CMV early and late genes were performed by polymerase chain reaction (PCR) on genomic peripheral blood DNA. Serum antibodies for CMV were determined by enzyme-linked immunosorbent assay.

RESULTS

From 114 families, we identified 11 sets of monozygotic twins and 3 sets of dizygotic twins. The concordance rate was 55% for monozygotic twins and 0% for fraternal twins. Most identical twins were male. The severity of the AA phenotype varied and appeared most severe in the first affected twin. Five of 24 twins were CMV seropositive but CMV DNA was not detected in blood lymphocytes of any of the subjects when studied after the onset of AA. The presence of AA in twins was not correlated with evidence of CMV.

CONCLUSION

A 55% concordance rate in identical twins and AA occurring in families support a genetic component as well as possible environmental triggers that remain unknown.

HLA and clinical associations in systemic sclerosis patients with anti-Th/To antibodies

OBJECTIVE

To determine the clinical and immunogenetic features of systemic sclerosis (SSc) patients with anti-Th/To autoantibodies.

METHODS

HLA class II alleles were determined by DNA oligotyping in a large group of SSc patients with anticentromere antibodies (ACA), anti-topoisomerase I (anti-topo I), and anti-Th/To autoantibodies.

RESULTS

Clinical features of the 28 anti-Th/To-positive SSc patients were similar to those observed in the 56 ACA-positive SSc patients, except for a decreased frequency of gastrointestinal involvement in anti-Th/To-positive patients. Immunogenetic analysis revealed a significant increase in the frequency of HLA-DR11 in the anti-Th/To-positive and the anti-topo I-positive patients. The anti-Th/To-positive patients also had a significant reduction in the frequency of HLA-DR7, similar to that seen in ACA-positive SSc patients.

CONCLUSION

Despite clinical and immunogenetic similarities with both the ACA- and anti-topo I-positive patients, anti-Th/To-positive SSc patients present a characteristic pattern of clinical and immunogenetic features that may have implications regarding etiology, pathogenesis, and treatment.

Association of DM genes in systemic sclerosis is secondary to the association with HLA genes

The contribution of polymorphism of DMA and DMB alleles to the pathogenesis of Japanese Systemic Sclerosis (SSc) was studied in 55 Japanese SSc patients and 77 normal Japanese subjects using the PCR-RFLP (restriction fragment length polymorphism) method. The allele frequencies of DMB*0101 allele were increased in SSc with diffuse scleroderma (70.0% vs 49.4%, p < 0.05, pc = not significant (NS)) and in SSc with antitopoisomerase I antibody (a-Scl-70), (68.2%, p < 0.05, pc = NS). The phenotype frequencies of DMB*0101 in these subgroups of SSc were increased significantly (95.0%, p = 0.014, pc < 0.05; 95.5%, p = 0.0088, pc < 0.05, respectively). In contrast, DMB*0102 and DMB*0103 alleles tended to decrease in diffuse scleroderma and SSc with a-Scl-70, but the decreases were not significant. Association analysis among DMA, DMB, and DRB1*1502 in Japanese SSc with diffuse scleroderma and SSc with a-Scl-70 indicated that the increase in DMA*0101 was not primary, but reflected an increase in HLA DRB1*1502.

Antinuclear antibody in systemic sclerosis (scleroderma)

The presence of autoantibodies to intracellular molecules is the hallmark immunologic finding of SSc. Recent sophisticated methods have contributed to characterization of unidentified antigens of ANA in sera from patients with SSc. Antibodies to RNA polymerases are the third major SSc-specific ANA, in addition to anti-topo I and anticentromere antibodies, and it is now possible to identify over 85% of SSc patients. These antibodies have proved helpful in diagnosis of this disease. An immunogenetic predisposition to synthesis of the ANAs has been unveiled. Both antigen-driven and molecular mimicry hypotheses have been proposed for ANA production in SSc. Although the role of ANAs in the pathogenesis of SSc is not yet known, it is logical to assume that the origin of ANAs is linked to the causes of this disease because each antibody is associated with its own unique constellation of clinical features.

Immunopathogenesis of systemic sclerosis

The information outlined above can be used to generate a model of the immunopathogenesis of SSc (Fig. 3). This model includes a susceptible host, with age greater than 25 and female gender being risk factors. The model also includes exposure to exogenous agents, which could be different in different individuals and may include inhaled or ingested chemicals or infectious agents. An early event is T-cell activation, with infiltration in the skin and internal organs. Activation of the T cells is a selective process that appears to be influenced by antigen in SSc patients. The importance of a particular T-cell subpopulation may depend upon the organ involved and the stage of the disease. CD4+ T cells predominate in the skin. In contrast, CD8+ T cells are increased in the lungs of patients with alveolitis, where they are oligoclonal, showing evidence of antigen-driven selection. V delta 1+ gamma/delta T cells are increased in both the blood and lungs of SSc patients and also show evidence of selection by antigen. B cells are activated early, with polyclonal activation leading to hypergammaglobulinemia. SSc-specific autoantibodies target DNA topoisomerase I, centromeric proteins, and RNA polymerases I and III. Characteristics of autoantibodies in SSc suggest that the target antigens are presented to the immune system as native molecules or even part of a multiunit complex. There is some homology between viruses and autoantibody targets in SSc, which suggests that molecular mimicry may play a role in initiating the antibody response. Many nonspecific inflammatory cells infiltrate the tissues and show evidence of activation. These include macrophages and monocytes, mast cells, eosinophils, basophils, and natural killer cells. Soluble mediators made by these T cells, B cells, and nonspecific inflammatory cells can activate and damage fibroblasts, endothelial cells, and other vascular cells. The relative importance of the various candidate cytokines, the temporal sequence of their production, and their cellular sources remain largely to be defined. There may be some contribution of direct T-cell cytotoxicity or antibody-dependent cellular cytoxicity to the tissue damage that occurs.

HLA-DR5 and DQB1*03 class II alleles are associated with cutaneous T-cell lymphoma

Cutaneous T-cell lymphoma (CTCL) may present with eczematous lesions, mycosis fungoides (MF), or as exfoliative erythroderma with circulating atypical cells, Sezary syndrome (SS). The "malignant" T cells are epidermotropic and clonal, but whether they respond to antigen stimulation is unknown. Because CD4+ lymphocytes recognize antigen presented by histocompatibility locus antigen (HLA) class II molecules, and HLA association have been found in autoimmune skin diseases, we determined by allele-specific oligonucleotide typing whether HLA-DR or DQ alleles were associated with CTCL and its two variants MF (n = 47) and SS (n = 23). Phenotypic frequencies were compared by chi-square and Fisher exact test, and p values were corrected independently for either 12 DR or 15 DQ alleles. HLA-DR5, previously associated with MF, was significantly increased in all 70 CTCL patients (31.5%) versus controls (11%) (uncorrected p value [Pnc] = 0.000038, odds ratio [OR] = 3.9, 1.9 < OR < 8.1), in MF patients (34%) (Pnc = 0.000047, OR = 3.62, 1.9 < OR < 10), and in SS patients (26%) (Pnc = 0.03, OR = 3, 0.9 < OR < 9.3). HLA-DQB1*03 alleles (0301, 0302, and 0303) were increased in 72% of all CTCL patients versus 49% of controls (corrected p value [Pc] = 0.014, OR = 2.7, 1.4 < OR < 5.1), in SS (82%) (Pc = 0.05, OR = 4.7, 1.4 < OR < 5), and in MF (67%) (Pnc = 0.024, OR = 2.15, 1 < OR < 4.5). DQB1*0502 was strongly increased in SS patients (Pc = 0.045, OR = 7.75, 1.25 < OR < 48). Although HLA-DQB1*0603 and HLA-DR6 (1301, 1302, and 1402) were decreased in all groups, the decreases were not statistically significant. These data suggest that certain HLA-DRB and DQB1 alleles, also associated with other T-cell-mediated skin diseases, may participate in the pathogenesis of or susceptibility to CTCL.

The centromere kinesin-like protein, CENP-E. An autoantigen in systemic sclerosis

OBJECTIVE

Autoantibodies directed against centromere proteins (CENPs) are a serologic feature in some patients with systemic sclerosis (SSc). Previous studies have focused on autoantibodies to CENPs A, B, and C. CENP-E is a recently described 312-kd protein that also localizes to the centromere. Therefore, we studied the presence of autoantibodies to recombinant CENP-E in patients with SSc.

METHODS

Sixty sera from patients with the SSc spectrum of diseases were screened for the presence of autoantibodies against CENP-E, by indirect immunofluorescence and immunoblotting using recombinant CENP-E protein. HLA class II alleles were determined by DNA oligotyping.

RESULTS

Among the SSc sera, 15 of 60 (25%) demonstrated antibody reactivity with recombinant CENP-E, and 14 of these 15 sera (93%) had antibodies directed against another CENP. Anti-CENP-E was seen in 13 of 30 sera with anti-CENP (43%). All patients with anti-CENP-E had a limited form of SSc, known as the CREST variant (calcinosis, Raynaud's phenomenon, esophageal dysmotility, sclerodactyly, telangiectasias). When patients with anti-CENPs A, B, or C were compared with patients with anti-CENP-E, no unique clinical features in the anti-CENP-E positive group were identified. Ninety-three percent of the patients with anti-CENP-E had HLA-DQB1 alleles that had polar amino acids at position 26 (primarily DQB1*05), similar to patients with other CENP autoantibodies.

CONCLUSION

Antibodies to CENP-E are common in patients with SSc, and are seen in higher frequency in sera from patients with a limited form, or CREST variant, of the disease.

Increased prevalence of systemic sclerosis in a Native American tribe in Oklahoma. Association with an Amerindian HLA haplotype

OBJECTIVE

To investigate a high prevalence of systemic sclerosis (SSc; scleroderma) in a well-defined population of 21,255 Choctaw Indians residing in 8 southeastern Oklahoma counties who were "users" of Indian Health Services.

METHODS

A case-control study of 12 SSc cases and 48 matched non-SSc controls (4 per case) was conducted to investigate potential occupational, residential, and infectious exposures, as well as genetic factors which might predispose to SSc. HLA class II alleles were determined by DNA oligotyping, and class I and III alleles were defined serologically.

RESULTS

The prevalence of SSc in full-blooded Choctaws was at least 8/1,704, or 469/100,000 (95% confidence interval [95% CI] 203-930) over the 4-year interval 1990-1994 and was significantly higher than that among non-full-blooded Choctaws (6/19,551, or 31/100,000) (P = 0.00001, odds ratio [OR] = 15.4, 95% CI 4.9-49.8). The overall prevalence of SSc in Oklahoma Choctaws (66/100,000) also was significantly higher than that in other Native Americans in Oklahoma (9.5/100,000) (P = 10(-6), OR = 6.95, 95% CI 3.3-13.7), who showed a prevalence similar to that reported for whites (2.1-25.3/100,000). Among the SSc cases, there was striking homogeneity of disease expression with the majority exhibiting diffuse scleroderma, pulmonary fibrosis, and autoantibodies to topoisomerase I. No environmental exposures were found to be in excess among cases versus controls. The strongest risk factor for SSc in cases (100%) versus controls (54%) was an HLA haplotype bearing the alleles B35, Cw4, DRB1*1602 (DR2), DQA1*0501, and DQB1*0301 (DQ7) (P = 0.002, Pcorr = 0.036, OR = 21, 95% CI 2.9-437). Survey of another group of Choctaws residing in another state revealed no cases of SSc despite a high frequency of the same HLA haplotype.

CONCLUSION

Full-blooded Choctaw Native Americans living in southeastern Oklahoma have the highest prevalence of SSc yet found in any population. A major risk factor for disease is a uniquely Amerindian HLA haplotype; however, additional genes and/or an as-yet-unidentified environmental exposure seem likely.

Autoantibodies to fibrillarin in systemic sclerosis (scleroderma). An immunogenetic, serologic, and clinical analysis

OBJECTIVE

To determine the frequency, clinical associations, and any major histocompatibility complex correlations of antifibrillarin antibodies in patients with systemic sclerosis (SSc).

METHODS

Antifibrillarin antibodies were determined by indirect immunofluorescence, immunoblotting, and immunoprecipitation, and HLA class II alleles by DNA oligotyping, in a large cohort of SSc patients.

RESULTS

Antifibrillarin was found in 8% of 335 SSc sera and was significantly more common in blacks (16%) than whites (5%), in males (33%) than females (14%), and in patients with cardiac, renal, or gut involvement. The HLA class II haplotype DRB1*1302, DQB1*0604 was found significantly more frequently in SSc patients with antifibrillarin compared with race-matched normal controls and 260 SSc patients without antifibrillarin. In addition, 1 or more of the HLA-DQB1 alleles *0604, *0301, *0602, and/or *0302 was found in all antifibrillarin-positive patients, and 62% of the antifibrillarin-positive patients had 2 of these HLA-DQB1 alleles, a highly significant difference from both race-matched normal controls and antifibrillarin-negative SSc patients.

CONCLUSION

Antifibrillarin, although an infrequent nucleolar autoantibody, is a marker for severe SSc, especially in blacks and males, and is strongly associated with a unique HLA haplotype, as well as with combinations of certain HLA-DQB1 alleles.

Autoimmunity in dilated cardiomyopathy and the major histocompatibility complex

Autoimmune mechanisms are likely to participate in the pathogenesis of a subgroup of dilated cardiomyopathy. These mechanisms involve the elaboration of autoantibodies against cardiac proteins as well as abnormal lymphocyte regulation. The presence of autoantibodies against beta-adrenoceptors correlates with the human leukocyte antigen (HLA)-DR4/1 phenotypes and specific T-cell receptor haplotypes. In addition, histidine at position 36 of the HLA-DQ beta 1 gene is associated with the presence of clinically manifest dilated cardiomyopathy. Components of the major histocompatibility complex (MHC) may thus serve as markers for the propensity to develop immune-mediated myocardial damage.

Strong association of dermatomyositis-specific Mi-2 autoantibodies with a tryptophan at position 9 of the HLA-DR beta chain

OBJECTIVE

To characterize the clinical and immunogenetic features of patients with Mi-2 autoantibodies.

METHODS

Eighteen adult white patients with Mi-2 antibodies were clinically characterized and compared with 41 Mi-2-negative dermatomyositis (DM) patients. HLA class I and class II typing for DRB alleles was done by microcytotoxicity assay and for DQA and DQB alleles by polymerase chain reaction-based oligotyping.

RESULTS

Seventeen of the 18 Mi-2-positive patients had DM. Symptoms of scleroderma, lung involvement, and arthritis were less common in this group than in the Mi-2-negative DM patients; the V-sign rash and nailfold involvement were found more frequently. Mi-2 antibodies were strongly associated with HLA-DR7 (88% versus 24% in healthy controls), HLA-DQA1*0201 (86% versus 23%), and DR7 "homozygosity" (31% versus 0%). A tryptophan residue at position 9 of the HLA-DR beta chain was present in all Mi-2-positive patients (100% versus 62%; homozygous in 81% versus 15%).

CONCLUSION

Our results reemphasize the specificity of Mi-2 antibodies for DM, and extend previous reports that Mi-2 antibody production is associated with certain HLA class II antigens. We propose beta 9-Trp as a candidate epitope on the HLA-DR beta chain as a prerequisite for this type of autoimmune response.

Clinical relevance of autoantibodies in systemic rheumatic diseases

Autoantibodies directed to intracellular antigens are serological hallmarks of systemic rheumatic diseases. Identification of circulating autoantibodies is helpful in establishing the correct diagnosis, indicating the prognosis and providing a guide to treatment and follow-up. Some autoantibodies are included in diagnostic and classification criteria for diseases such as anti-Sm antigen and anti-double-stranded DNA antibodies in systemic lupus erythematosus, anti-U1 nuclear ribonucleoprotein antibodies in mixed connective tissue disease, and anti-SS-A/Ro and anti-SS-B/La antibodies in Sjögren's syndrome. Over the past 30 years, the identification of new autoantibody systems was advanced by the initiation or adaptation of novel techniques such as double immunodiffusion to detect antibodies to saline-soluble nuclear antigens, extraction-reconstitution and ELISA techniques to detect histone and chromatin antibodies, immunoblotting and immunoprecipitation to detect a wide range of antibodies directed against naturally occurring and recombinant proteins. These techniques have been made possible by advances in cellular and molecular biology and in turn, the sera from index patients have been important reagents to identify novel intracellular macromolecules. This paper will focus on the clinical relevance of several autoantibody systems described by Tan and his colleagues over the past 30 years.

Segregation of autoantibodies with disease in monozygotic twin pairs discordant for systemic sclerosis. Three further cases

OBJECTIVE

To study the serologic status of 3 previously unreported monozygotic twin pairs discordant for systemic sclerosis (SSc).

METHODS

Autoantibodies were measured by indirect immunofluorescence, immunodiffusion, and immunoprecipitation of 35S-labeled cell lines. Major histocompatibility complex (MHC) class II allele typing and DNA fingerprinting were used to confirm monozygosity.

RESULTS

Anti-PM-Scl, anti-threonyl transfer RNA synthetase, and anti-topoisomerase I antibodies, respectively, were found in each of the twins with SSc. None of the unaffected twin siblings had an identifiable autoantibody, although serum from 1 unaffected twin precipitated several unknown proteins. The MHC class II genotype in each twin was the genotype expected for the autoantibody that was present.

CONCLUSION

Autoantibodies of certain defined specificities are intimately linked with the development of SSc, because they segregate with SSc in individuals who start life with identical germline genes.

HLA class II genes associated with anticentromere antibody in Japanese patients with systemic sclerosis (scleroderma)

OBJECTIVE

To define further HLA class II gene associations with anticentromere antibody (ACA), a major serum antinuclear antibody in patients with systemic sclerosis (SSc).

METHODS

HLA class II genes were determined using polymerase chain reaction/restriction fragment length polymorphisms in 94 Japanese patients with SSc (22 ACA positive and 72 ACA negative) and 50 race matched normal control subjects.

RESULTS

Frequency of DQB1*0501 was increased in ACA positive SSc patients compared with ACA negative SSc patients (36% versus 13%; p = 0.02, odds ratio = 4.0, 95% confidence interval 1.1 to 13.9), but the association of ACA with a polar amino acid at position 26 in the DQB1 beta 1 domain, which was demonstrated in white North Americans, was not observed in Japanese. The DRB1*0101, *0405, and *1302 alleles were associated with high ACA titres, whereas DRB1*1502 was associated with low ACA titres and a low frequency of centromere protein C (CENP-C) reactivity.

CONCLUSIONS

These results suggest that the ACA response is associated with multiple HLA class II genes and that ACA positive SSc patients are heterogeneous in terms of immunogenetic background.

Possible involvement of the HLA-DQB1 gene in susceptibility and resistance to human dilated cardiomyopathy

There is evidence that autoimmunity plays a role in the pathogenesis of dilated cardiomyopathy and that susceptibility to the disease is related to products of human leukocyte antigens (HLA) class II genes. We compared the distribution of HLA-DQA1 and -DQB1 alleles and haplotypes in 44 normal controls and 34 patients with idiopathic dilated cardiomyopathy patients. The distribution of two DQA1-DQB1 haplotypes (*0102-*0604 and *0102-*0501) were more frequent in the patients. Histidine at position 30 of the HLA-DQB1 gene was associated with disease (62% of patients compared to 36% of controls), whereas homozygosity for leucine at position 26 was more frequent in controls (36% vs 18% of patients). There was no correlation between HLA-DQA1-DQB1 haplotypes and the presence of anti-beta-receptor antibodies. These results suggest that the HLA-DQB1 gene is involved in the pathogenesis of human dilated cardiomyopathy.

Major histocompatibility complex class II gene associations with anti-U1 small nuclear ribonucleoprotein antibody. Relationship to immunoreactivity with individual constituent proteins

OBJECTIVE

To better define immunogenetic associations with the anti-U1 ribonucleoprotein (U1 RNP) autoantibody response.

METHODS

HLA class II alleles were determined by genotyping in 49 Japanese rheumatic disease patients with anti-U1 RNP antibody and 43 race-matched healthy controls. Immunoreactivities to U1 RNP constituent proteins (70K, A, B/B', and C) were detected by immunoblots using purified HeLa cell Sm antigen, and antibody titer was determined by passive hemagglutination assay.

RESULTS

DQB1*0302 was significantly more frequent in anti-U1 RNP-positive patients than in controls (43% versus 14%; odds ratio [OR] = 4.6, corrected P = 0.03). All anti-U1 RNP-positive patients had either a DQB1*0601, *0602, *0301, *0302, or *0303 allele, which share tyrosine at position 30, and the amino acid sequence Thr, Arg, Ala, Glu, Leu, Asp, and Thr at positions 71-77 in the DQB1 beta 1 domain. In contrast, one of these alleles was found in 81% of the controls (OR = 24, P = 0.002). In addition, anti-U1 RNP antibody was associated with unique DQB1*0302; DRB1*0401 haplotype. Anti-70K reactivity and antibody titer were positively associated with a basic amino acid residue, arginine or histidine, at position 13 (DR2 or DR4) and were negatively associated with the amino acid sequence Ile, Leu, Glu, and Asp at positions 67-70, which was present in some of the DR5-, DR6-, and DR8-associated alleles, in the DRB1 beta 1 domain. Anti-C reactivity was strongly associated with DR2, particularly with DRB1*1502.

CONCLUSION

The several shared epitopes located on HLA-DRB1 and DQB1 genes control the anti-U1 RNP autoantibody response.

HLA and autoimmunity in scleroderma (systemic sclerosis)

Scleroderma or systemic sclerosis (SSc) has been associated with certain class II antigens of the major histocompatibility complex (MHC), including HLA-DR1, DR2, DR3, DR5, and DR52. In general, these earlier HLA correlations were weak and varied considerably among reporting centers and different ethnic populations. More recently, a variety of disease-specific autoantibodies have been discovered including anti-centromere, antitopoisomerase I, and a variety of anti-nucleolar antibodies. These specificities show little overlap among one another, and each are markers for certain clinical features of SSc. At the same time, molecular studies of the MHC have provided more accurate methods for defining specific HLA alleles. Now it is becoming clear that certain HLA class II alleles, especially HLA-DQ, are more strongly associated with autoantibody subsets of SSc than with the disease itself. For example, anticentromere antibodies are strongly associated with HLA-DQB1*0501 (DQ5), DQB1*0301 (DQ7) and other DQB1 alleles possessing a glycine or tyrosine residue in position 26 of the outermost domain. Anti-topoisomerase I antibodies occur in SSc patients with HLA-DQB1*0301 (DQ7), DQB1*0302 (DQ8), DQB1*0601 (DQ6 in Japanese), and other DQB1 alleles possessing a tyrosine residue in position 30. HLA-DQ alleles associated with these autoantibodies tend to be in linkage disequilibrium with the HLA-DR specificities previously associated weakly with SSc itself. Rare multiplex families with SSc also show these same HLA haplotypes co-segregating with autoantibody profiles in affected members. Thus, it appears that MHC alleles play a role in affecting the serological expression of SSc, and the implications of these recent findings are discussed.

The role of the trimolecular complex (alpha beta TCR-MHC+peptide) in the pathogenesis of systemic sclerosis

Systemic sclerosis is an intricate disease process whose most unique and specific parameter indicative of autoimmunity is the presence of autoantibodies directed against certain nuclear antigens. The relationship between this particular humoral immune response and the genesis of a fibrotic tissue response in the skin as well as internal organs is not yet well understood. The prominence of CD4 T-cell infiltration during early phases of disease suggest that activation pathways may be initiated which subsequently result in phenotypic changes of a variety of mesenchymal cells, especially endothelial cells and fibroblasts. Taken in concert with the association of susceptibility with certain MHC class II molecules, the conventional presenters of exogenous peptide to T cells of the CD4 lineage, the notion of a central critical immune recognition event underlying the development of systemic sclerosis gains increasing likelihood. In addition to the still incompletely understood paracrine pathways between immune response and fibrosis, there is a nearly complete void of knowledge concerning what peptide is recognized by the T-cell and the structure of the alpha beta TCR involved in this recognition. Determining the role of the alpha beta TCR in the activation of the T-cell population in terms of identifying structural features which are critical participants in this process and the functional derangement leading to the characteristic pattern of self recognition will certainly enhance our understanding of the pathogenesis of systemic sclerosis.

HLA and ethnic associations among systemic sclerosis patients with anticentromere antibodies

SSc with ACAs is characterized by limited cutaneous involvement and, in most patients, a mild protracted course. We have studied 104 SSc patients, 47 with ACAs and 57 who were negative for both ACAs and anti-topo I antibodies, for HLA-DR and -DQ associations using DNA typing techniques. Normal controls consisted of 181 healthy individuals. A significant association was observed in the ACA-positive patients with DQB1-0501 (p = 0.001, RR 2.6). There was also a significant decrease in the frequency of DQB1-0201 (p = 0.01, RR 0.33). In addition, the ACA-positive SSc patients were significantly different ethnically from both the other SSc patients and the normal controls (p = 0.004). When patients were stratified according to their ethnic origin and the analysis of HLA associations was repeated, the HLA associations persisted. These results strongly suggest that the development of SSc with ACAs is associated with particular DQB1 alleles, and also that ethnic origin plays a role in disease susceptibility.

Role of hydrophobic and hydrophilic forces in peptide-protein interaction: new advances

A considerable part of important biological processes is governed by the noncovalent association of peptides and proteins. Various types of intermolecular forces may be involved in the formation of these molecular assemblies. This review gives a brief account of the physicochemical bases of interactive forces, with special emphasis on their impact on various peptide-protein interactions; summarizes the newest biochemical and biophysical methods for the study of such interactions; and discusses the role of various hydrophilic and hydrophobic forces in peptide-protein interactions in various fields of life sciences, such as immunology, enzymology, receptor binding, and toxicology.