MHC class II, tumour necrosis factor alpha, and lymphotoxin alpha gene haplotype associations with serological subsets of systemic lupus erythematosus

Host and bacterial factors linking periodontitis and rheumatoid arthritis

Observations from numerous clinical, epidemiological and serological studies link periodontitis with severity and progression of rheumatoid arthritis. The strong association is observed despite totally different aetiology of these two diseases, periodontitis being driven by dysbiotic microbial flora on the tooth surface below the gum line, while rheumatoid arthritis being the autoimmune disease powered by anti-citrullinated protein antibodies (ACPAs). Here we discuss genetic and environmental risk factors underlying development of both diseases with special emphasis on bacteria implicated in pathogenicity of periodontitis. Individual periodontal pathogens and their virulence factors are argued as potentially contributing to putative causative link between periodontal infection and initiation of a chain of events leading to breakdown of immunotolerance and development of ACPAs. In this respect peptidylarginine deiminase, an enzyme unique among prokaryotes for Porphyromonas gingivalis, is elaborated as a potential mechanistic link between this major periodontal pathogen and initiation of rheumatoid arthritis development.

Human leucocyte antigens profiling in Malay female patients with systemic lupus erythematosus: are we the same or different?

OBJECTIVE

SLE is a heterogeneous autoimmune disease, in terms of clinical presentation, incidence and severity across diverse ethnic populations. We investigated the human leucocyte antigens (HLA) profile (ie, HLA-A, HLA-B and HLA-C, HLA-DRB1, HLA-DQA1, HLA-DQB1, HLA-DPA1 and HLA-DPB1) in Malaysian Malay female patients with SLE and determined the generalisability of the published HLA risk factors across different ethnic populations globally including Malaysia.

METHODS

One hundred Malay female patients with SLE were recruited between January 2016 and October 2017 from a nephrology clinic. All patients were genotyped for HLA-A, HLA-B, HLA-C, HLA-DRB1, HLA-DQA1, HLA-DQB1, HLA-DPA1 and HLA-DPB1 alleles using PCR sequence-specific oligonucleotides method on Luminex platform. A total of 951 HLA genotyped population-based Malay control subjects was used for association testing by means of OR with 95% CIs.

RESULTS

Our findings convincingly validated common associations between HLA-A*11 (OR=1.65, p=3.36×10^-3, corrected P (Pc)=4.03×10^-2) and DQB1*05:01 (OR=1.56, p=2.02×10^-2, Pc=non-significant) and SLE susceptibility in the Malay population. In contrast, DQB1*03:01 (OR=0.51, p=4.06×10^-4, Pc=6.50×10^-3) were associated with decreased risk of SLE in Malay population. Additionally, we also detected novel associations of susceptibility HLA genes (ie, HLA-B*38:02, DPA1*02:02, DPB1*14:01) and protective HLA genes (ie, DPA1*01:03). When comparing the current data with data from previously published studies from Caucasian, African and Asian populations, DRB1*15 alleles, DQB1*03:01 and DQA1*01:02 were corroborated as universal susceptibility and protective genes.

CONCLUSIONS

This study reveals multiple HLA alleles associated with susceptibility and protection against risk of developing SLE in Malay female population with renal disorders. In addition, the published data from different ethnic populations together with our study further support the notion that the genetic effects from association with DRB1*15:01/02, DQB1*03:01 and DQA1*01:02 alleles are generalised to multiple ethnic populations of Caucasian, African and Asian descents.

Association of HLA-DR3 and HLA-DR15 Polymorphisms with Risk of Systemic Lupus Erythematosus

Background:

Systemic lupus erythematosus (SLE) is an autoimmune disease under genetic control. Growing evidences support the genetic predisposition of HLA-DRB1 gene polymorphisms to SLE, yet the results are not often reproducible. The purpose of this study was to assess the association of two polymorphisms of HLA-DRB1 gene (HLA-DR3 and HLA-DR15) with the risk of SLE via a comprehensive meta-analysis.

Methods:

This study complied with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement. Case-control studies on HLA-DRB1 and SLE were searched from PubMed, Elsevier Science, Springer Link, Medline, and Cochrane Library database as of June 2018. Analysis was based on the random-effects model using STATA software version 14.0.

Results:

A total of 23 studies were retained for analysis, including 5261 cases and 9838 controls. Overall analysis revealed that HLA-DR3 and HLA-DR15 polymorphisms were associated with the significant risk of SLE (odds ratio [OR]: 1.60, 95% confidence interval (CI): 1.316–1.934, P = 0.129 and OR: 1.68, 95% CI: 1.334–2.112, P = 0.001, respectively). Subgroup analyses demonstrated that for both HLA-DR3 and HLA-DR15 polymorphisms, ethnicity was a possible source of heterogeneity. Specifically, HLA-DR3 polymorphism was not associated with SLE in White populations (OR: 1.60, 95% CI: 1.320–1.960, P = 0.522) and HLA-DR15 polymorphism in East Asian populations (OR: 1.65, 95% CI: 1.248–2.173, P = 0.001). In addition, source of control was another possible source for both HLA-DR3 and HLA-DR15 polymorphisms, with observable significance for HLA-DR3 in only population-based studies (OR: 1.65, 95% CI: 1.370–1.990, P = 0.244) and for HLA-DR15 in both population-based and hospital-based studies (OR: 1.38, 95% CI: 1.078–1.760, P = 0.123 and OR: 2.08, 95% CI: 1.738–2.490, P = 0.881, respectively).

Conclusions:

HLA-DRB1 gene may be a SLE-susceptibility gene, and it shows evident ethnic heterogeneity. Further prospective validations across multiple ethnical groups are warranted.

Association between tumor necrosis factor polymorphisms and rheumatoid arthritis as well as systemic lupus erythematosus: a meta-analysis

Tumor necrosis factor-alpha (TNF-α) plays an important role in autoimmune diseases. Previous studies have investigated the association of TNF-α-238G/A (rs361525) and -308G/A (rs1800629) polymorphisms with rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE). However, no agreed conclusion had been made. Therefore, this meta-analysis was conducted to assess the associations of TNF-α-238G/A and -308G/A polymorphisms with RA and SLE risk. A systematic search was conducted in commonly used databases. Meta-analysis was performed by STATA12.0. A total of 43 studies were included. In the overall population, the TNF-α-238A allele was observed to be a protective factor for RA (A vs G: OR=0.75, 95%CI=0.57–0.99, P=0.040) and the TNF-α-308A allele was found to be a risk factor for SLE (A vs G: OR=1.78, 95%CI=1.45–2.19, P<0.001). However, no evidence of association was found between TNF-α-238 G/A polymorphism and SLE nor between -308G/A and RA. In the subgroup analysis, TNF-α-308A allele played a pathogenic role for RA in Latin Americans (A vs G: OR=1.46, 95%CI=1.15–1.84, P=0.002) and for SLE in Latin Americans (A vs G: OR=2.12, 95%CI=1.32–3.41, P=0.002) and Europeans (A vs G: OR=2.03, 95%CI=1.56–2.63, P<0.001), while it played a protective role for RA in Asians (A vs G: OR=0.54, 95%CI=0.32–0.90, P=0.017). No significant association was found between TNF-α-308G/A and SLE susceptibility in Africans and Asians. This meta-analysis demonstrated that TNF-α-238A was associated with decreased risk of RA rather than SLE, while -308G/A polymorphism was associated with SLE rather than RA. Stratification analysis indicated that different ethnicities would have different risk alleles.

Nature of T cell epitopes in lupus antigens and HLA-DR determines autoantibody initiation and diversification

OBJECTIVES

The generation of systemic lupus erythematosus (SLE)-related autoantibodies have been shown to be T cell dependent and antigen driven with HLA-DR restriction. In this study, the initiating antigen(s) and the mechanism of autoantibody diversification were investigated.

METHODS

T cell epitopes (T-epitopes) of SmD1 (SmD) were mapped by T-T hybridomas generated from DR3⁺AE⁰ mice immunised with SmD and with SmD overlapping peptides. TCRs from the reactive hybridomas were sequenced. The core epitopes were determined. Bacterial mimics were identified by bioinformatics. Sera from DR3⁺AE⁰ mice immunised with SmD peptides and their mimics were analysed for their reactivity by ELISA and immunohistochemistry. Samples of blood donors were analysed for HLA-DR and autoantibody specificities.

RESULTS

Multiple HLA-DR3 restricted T-epitopes within SmD were identified. Many T-T hybridomas reacted with more than one epitope. Some of them were cross-reactive with other snRNP peptides and with proteins in the Ro60/La/Ro52 complex. The reactive hybridomas used unique TCRs. Multiple T-epitope mimics were identified in commensal and environmental bacteria. Certain bacterial mimics shared both T and B cell epitopes with the related SmD peptide. Bacterial mimics induced autoantibodies to lupus-related antigens and to different tissues. HLA-DR3⁺ blood donors made significantly more SLE-related autoantibodies.

CONCLUSIONS

The unique antigenic structures of the lupus-related autoantigens provide the basis for being targeted and for T and B cell epitope spreading and autoantibody diversification with unique patterns. SLE-related autoantibodies are likely generated from responses to commensal and/or environmental microbes due to incomplete negative selection for autoreactive T cells. The production of SLE-related antibodies is inevitable in normal individuals. The findings in this investigation have significant implications in autoimmunity in general.

Type 3 innate lymphoid cell-derived lymphotoxin prevents microbiota-dependent inflammation

Splenomegaly is a well-known phenomenon typically associated with inflammation. However, the underlying cause of this phenotype has not been well characterized. Furthermore, the splenomegaly phenotype seen in lymphotoxin (LT) signaling-deficient mice is characterized by increased numbers of splenocytes and splenic neutrophils. Splenomegaly, as well as the related phenotype of increased lymphocyte counts in non-lymphoid tissues, is thought to result from the absence of secondary lymphoid tissues in LT-deficient mice. We now present evidence that mice deficient in LTα1β2 or LTβR develop splenomegaly and increased numbers of lymphocytes in non-lymphoid tissues in a microbiota-dependent manner. Antibiotic administration to LTα1β2- or LTβR-deficient mice reduces splenomegaly. Furthermore, re-derived germ-free Ltbr-/- mice do not exhibit splenomegaly or increased inflammation in non-lymphoid tissues compared to specific pathogen-free Ltbr-/- mice. By using various LTβ- and LTβR-conditional knockout mice, we demonstrate that retinoic acid-related orphan receptor γT-positive type 3 innate lymphoid cells provide the required active LT signaling to prevent the development of splenomegaly. Thus, this study demonstrates the importance of LT-mediated immune responses for the prevention of splenomegaly and systemic inflammation induced by microbiota.

Human leukocyte antigens-DRB1*03 is associated with systemic lupus erythematosus and anti-SSB production in South Tunisia

INTRODUCTION

Systemic lupus erythematosus (SLE) is an autoimmune disease with various presentations. This variation is due to the interaction of hormonal, environmental, and genetic factors. Associations between human leukocyte antigens and SLE have long been recognized in different ethnic populations and have been suggested to represent the most important association.

OBJECTIVES

The objectives of this paper were to determine susceptibility and protection human leukocyte antigens (HLA) Class II markers for SLE and to highlight, for the first time, associations between HLA alleles and clinical and serological features in South Tunisia.

METHODS

We conducted a case-control study on 75 SLE patients and 123 healthy controls. The HLA Class II DRB1/DQB1 of all patients and controls was genotyped using polymerase chain reaction-sequence specific primer technique. Statistical analysis was performed using SPSS software.

RESULTS

HLA-DRB1*03 was the principal Class II allele associated with the genetic susceptibility to SLE (pc = 0.02; OR = 2.57; CI = [1.39-4.75]; this allele was also associated with anti-SSB production (P = 0.016; OR = 4.00; CI = [1.24-12.96]). HLA-DRB1*01 was significantly more expressed in SLE patients with neurologic disorders (P = 0.013; OR = 20.25; CI = [1.87-219.21]). No allele was found to be protective against SLE in our study group.

CONCLUSION

Our results show that in South Tunisia SLE is associated with HLA-DRB1*03 and that some clinical features of SLE may be influenced by specific DRB1 and DQB1 alleles.

TLR response pathways in NuLi-1 cells and primary human nasal epithelial cells

The present study describes and compares functional properties of Nuli-1 cells and primary human nasal epithelial cells (HNEC) including TLR expression and function. Differences in gene expression were identified for non-TLR genes that play a role in TLR response pathways. However, experiments comparing TLR gene expression for both Nuli-1 cells and HNECs indicated conserved expression in both cell types. Stimulation of the two cell types resulted in a conserved response to TLR3 agonists, but in differences in response to agonists for TLR5 and TLR6/2. HNECs were much more susceptible to infection with Staphylococcus aureus than NuLi-1 cells. Furthermore, when cultured at air-liquid interface (ALI), NuLi-1 cells possessed much lower trans-epithelial resistance than primary HNEC and did not exhibit maintenance of cell morphology or mucous production which was observed in HNECs. Nor did they produce the characteristic interconnecting pattern of tight junction complexes at the apicolateral margin of adjacent cells. Caution should therefore be exercised when selecting cell lines for immunological studies and a thorough screen of properties relevant to the study should always be carried out prior to commencement.

Tumor necrosis factor-alpha single nucleotide polymorphisms in juvenile systemic lupus erythematosus

BACKGROUND

Juvenile systemic lupus erythematosus (JSLE) is a multi-system autoimmune disorder of unknown origin. Given the importance of the contribution of pro-inflammatory cytokines, including tumor necrosis factor-alpha (TNF-α), towards the pathogenesis of JSLE, this study was performed to assess TNFA gene polymorphisms in a case-control study.

METHODS

Fifty nine patients with JSLE were enrolled in this study as case group and compared with healthy control subjects. The frequency of alleles, genotypes, and haplotypes of TNFA single-nucleotide polymorphisms (SNPs) at positions -308 and -238 were evaluated, using polymerase chain reaction with sequence-specific primers method.

RESULTS

The G allele at position -238 in TNFA promoter region was significantly more frequent in patients with JSLE than in the healthy controls (P value<0.001), while the frequency of A allele at the same position was significantly lower than controls. Furthermore, a significant positive association for G/G genotype at the same position was detected in patients' group compared with control subjects (P value<0.001). The GA haplotype of TNFA (positions -308, -238) was significantly less frequent in case group than in controls (P value<0.001), while GG was the most frequent haplotype for TNFA in the patient group, compared to controls (P value<0.01).

CONCLUSIONS

Pro-inflammatory cytokine gene polymorphisms may influence susceptibility to JSLE. Particular TNFA gene variants are associated with JSLE and could be used as a genetic marker for susceptibility to JSLE.

Value of HLA-DR genotype in systemic lupus erythematosus and lupus nephritis: a meta-analysis

AIM

Human leukocyte antigen (HLA)-DRB1 allele polymorphisms have been reported to be associated with systemic lupus erythematosus (SLE) susceptibility, but the results of these previous studies have been inconsistent. The purpose of the present study was to systematically summarize and explore whether specific HLA-DRB1 alleles confer susceptibility or resistance to SLE and lupus nephritis.

METHODS

This review was guided by the preferred reporting items for systematic reviews and meta-analyses (PRISMA) approach. A comprehensive search was made for articles from PubMed, Medline, Elsevier Science, Springer Link and Cochrane Library database. A total of 25 case-control studies on the relationship between gene polymorphism of HLA-DRB l and SLE were performed and data were analyzed and processed using Review Manager 5.2 and Stata 11.0.

RESULTS

At the allelic level, HLA-DR4, DR11 and DR14 were identified as protective factors for SLE (0.79 [0.69,0.91], P < 0.001; 0.72 [0.60, 0.85], P < 0.0001; 0.47 [0.59, 0.95], P < 0.05, respectively). HLA-DR3, DR9, DR15 were potent risk factors for SLE (1.88 [1.58, 2.23], P < 0.001; 1.24 [1.07, 1.45], P < 0.05; 1.25 [1.10, 1.43], P < 0.001, respectively). However, HLA-DR8 was not statistically significant between the SLE group and control group (OR, 1.11 [0.96, 1.30], P > 0.05). DR4 and 11 (OR, 0.55 [0.39, 0.79], P < 0.01; 0.60 [0.37, 0.96], P < 0.05, respectively) conferred a significant protective effect for lupus nephritis. DR3 and DR15 (OR, 2.00 [1.49, 2.70], P < 0.05; 1.60 [1.21, 2.12], P < 0.001, respectively) were at a high risk of developing lupus nephritis. HLA-DR8, DR9 and DR14 (OR, 1.47 [0.9, 2.33], P > 0.05; 0.90 [0.64, 1.27], P > 0.05; 0.61 [0.36, 1.03], P > 0.05, respectively) were not statistically significant between the lupus nephritis and control groups.

CONCLUSIONS

The HLA-DR4, DR11, DR14 alleles might be protective factors for SLE and HLA-DR3, DR9, DR15 were potent risk factors. In addition, HLA-DR4 and DR11 alleles might be protective factors for lupus nephritis and DR3 and DR15 suggest a risk role. These results proved that HLA-DR3, DR15, DR4 and DR11 might be identified as predictors for lupus nephritis and SLE.

Association of TLR4 (D299G, T399I), TLR9 -1486T>C, TIRAP S180L and TNF-α promoter (-1031, -863, -857) polymorphisms with risk for systemic lupus erythematosus among South Indians

The rationale of this case-control study was to explore the association of Toll-like receptor 4 (TLR4) D299G, TLR4 T399I, TLR9 -1486 T>C, TIR-domain-containing adaptor protein (TIRAP) S180 L and tumor necrosis-α (TNF-α) promoter polymorphisms with susceptibility and phenotypic heterogeneity of systemic lupus erythematosus (SLE). PCR-RFLP, real-time PCR was used for the genetic analysis and expression studies and ELISA was used for the determination of specific autoantibodies. TLR4 D299G was associated with the risk for SLE (OR: 1.57, 95% CI: 1.08-2.28), while the TNF-α (-1031, -863, -857) CCC haplotype conferred protection. TLR4 and TIRAP polymorphisms were associated with reduced expression of HLA-DR. The presence of TLR4 and TLR9 polymorphisms increases the MHC2TA expression, while TIRAP polymorphism was associated with reduced expression. TLR4 D299 G showed an inverse association with pulmonary hypertension. TLR 4 T399I and TLR9 -1486 T>C showed a positive association with seizures and photosensitivity, respectively. TIRAP S180 L showed a positive association with alopecia and malar rashes, while an inverse association with psychosis was observed. TLR4 T399I (r = 0.14, p = 0.05) and TIRAP S180 L (r = 0.15, p = 0.03) showed a positive association with anti-Ro antibodies. On the other hand, TLR9 -1486 T>C showed an inverse association with anti-La antibodies (r = -0.20, p = 0.006). To conclude, TLR4 D299G increases the risk for SLE, while TNF-α CCC haplotype reduces the risk for SLE. All these polymorphisms contribute toward phenotypic heterogeneity. TLR4 T399I, TLR9 -1486 T>C and TIRAP S180 L influence specific autoantibody production in SLE.

Preferential HLA-DRB1*11–dependent presentation of CUB2-derived peptides by ADAMTS13-pulsed dendritic cells

ADAMTS13 derived peptides presented on HLA-DR; implications for acquired TTP. CUB2 domain peptide binds to risk-allele HLA-DRB1*11.

Tumor necrosis factor B (TNFB) genetic variants and its increased expression are associated with vitiligo susceptibility

Genetic polymorphisms in TNFB are involved in the regulation of its expression and are found to be associated with various autoimmune diseases. The aim of the present study was to determine whether TNFB +252A/G (rs909253) and exon 3 C/A (rs1041981) polymorphisms are associated with vitiligo susceptibility, and expression of TNFB and ICAM1 affects the disease onset and progression. We have earlier reported the role of TNFA in autoimmune pathogenesis of vitiligo, and we now show the involvement of TNFB in vitiligo pathogenesis. The two polymorphisms investigated in the TNFB were in strong linkage disequilibrium and significantly associated with vitiligo. TNFB and ICAM1 transcripts were significantly increased in patients compared to controls. Active vitiligo patients showed significant increase in TNFB transcripts compared to stable vitiligo. The genotype-phenotype analysis revealed that TNFB expression levels were higher in patients with GG and AA genotypes as compared to controls. Patients with the early age of onset and female patients showed higher TNFB and ICAM1 expression. Overall, our findings suggest that the increased TNFB transcript levels in vitiligo patients could result, at least in part, from variations at the genetic level which in turn leads to increased ICAM1 expression. For the first time, we show that TNFB +252A/G and exon 3 C/A polymorphisms are associated with vitiligo susceptibility and influence the TNFB and ICAM1 expression. Moreover, the study also emphasizes influence of TNFB and ICAM1 on the disease progression, onset and gender bias for developing vitiligo.

TNF-α and TGF-β counter-regulate PD-L1 expression on monocytes in systemic lupus erythematosus

Monocytes in patients with systemic lupus erythematosus (SLE) are hyperstimulatory for T lymphocytes. We previously found that the normal program for expression of a negative costimulatory molecule programmed death ligand-1 (PD-L1) is defective in SLE patients with active disease. Here, we investigated the mechanism for PD-L1 dysregulation on lupus monocytes. We found that PD-L1 expression on cultured SLE monocytes correlated with TNF-α expression. Exogenous TNF-α restored PD-L1 expression on lupus monocytes. Conversely, TGF-β inversely correlated with PD-L1 in SLE and suppressed expression of PD-L1 on healthy monocytes. Therefore, PD-L1 expression in monocytes is regulated by opposing actions of TNF-α and TGF-β. As PD-L1 functions to fine tune lymphocyte activation, dysregulation of cytokines resulting in reduced expression could lead to loss of peripheral T cell tolerance.

The role of Tumor Necrosis Factor-alpha (TNF-α) in the pathogenesis of systemic lupus erythematosus

The Tumor Necrosis Factor-alpha (TNF-α) is a pleiotropic cytokine that produces different stimuli in various physiological and pathological conditions. TNF-α contributes importantly to the development of T cells, B cells, and dendritic cells. However, TNF-α is also a potent inflammatory mediator and apoptosis inducer. The significance of the TNF-α involvement in the pathogenesis of systemic lupus erythematosus (SLE) remains controversial. From the genetic standpoint, a number of studies suggest that the TNF-α gene polymorphism is involved in the susceptibility of SLE. Moreover, there is a close association between the TNF-α gene expression and clinical manifestations. In addition, the increased serum level of TNF-α is observed in SLE patients and associated with disease activity and certain systemic manifestations. Treatment with anti-TNF agents is, however, controversial in SLE since induction of antinuclear antibodies, anti-dsDNA, anticardiolipin antibodies, and cases of drug-induced lupus have been observed in rheumatoid arthritis patients. In this context, this study reviewed the importance of TNF-α in the pathogenesis of SLE.

Association of TNF-α promoter-308 A/G polymorphism with susceptibility to systemic lupus erythematosus: a meta-analysis

Published data on the association between tumor necrosis factor-alpha (TNF-α) promoter-308 A/G polymorphism and systemic lupus erythematosus (SLE) risk are inconclusive. To derive a more precise estimation of the relationship, a meta-analysis was performed. A total of 28 studies including 2,992 cases and 4,326 controls (5,924 cases and 8,484 controls in A versus G comparison) were involved in this meta-analysis. Meta-analysis was performed for genotypes A/A (recessive effect), A/A+A/G (dominant effect), and A allele in fixed or random effects models. In addition, we also performed a "model-free" analysis by considering the G/G genotype as the reference and estimated the OR for the A/A versus G/G and A/G versus G/G genotype. Overall, an association of TNF-α promoter-308 A/G polymorphism with SLE was found (A versus G: OR = 1.686, 95% CI = 1.400-2.032, P < 0.001; A/A versus A/G+G/G: OR = 3.043, 95% CI = 2.185-4.238, P < 0.001; A/A+A/G versus G/G: OR = 1.822, 95% CI = 1.379-2.407, P < 0.001; A/A versus G/G: OR = 3.686, 95% CI = 2.628-5.172, P < 0.001; A/G versus G/G: OR = 1.691, 95% CI = 1.291-2.215, P < 0.001). However, stratification by ethnicity indicated that the risk A allele was not associated with SLE in Asian (A versus G: OR = 1.207, 95% CI = 0.856-1.702, P = 0.283) and African population (A versus G: OR = 1.225, 95% CI = 0.597-2.516, P = 0.580). In summary, this meta-analysis indicated that TNF-α promoter-308-A/G polymorphism is associated with susceptibility to SLE.

A comparison of restriction fragment length polymorphism, tetra primer amplification refractory mutation system PCR and unlabeled probe melting analysis for LTA+252 C>T SNP genotyping

BACKGROUND

From the wide range of methods currently available for genotyping, we wished to identify a quick, reliable and affordable approach for routine use in our laboratory for LTA+252 C>T SNP screening.

METHODS

We set up and compared three genotyping methods for SNP detection: restriction fragment length polymorphism (RFLP), tetra primer amplification refractory mutation system PCR (TPAP) and unlabeled probe melting analysis (UPMA). The SNP model used was LTA+252 C>T, a cytokine gene polymorphism that has been associated with response to treatment in rheumatoid arthritis. The study was performed using 46 samples from healthy Caucasian volunteers.

RESULTS

Allele and genotype distribution was similar to that previously described in the same population. All three genotyping methods showed good reproducibility and are suitable for a medium scale throughput molecular platform. UPMA was the most cost effective, reliable and safe method since it required the shortest technician time, could be performed in a single closed tube and involved automatic data analysis.

CONCLUSION

This work is the first to compare these three genotyping techniques and provides evidence for UPMA being the method of choice for LTA+252 C>T SNP genotyping.

Autoimmunity to specific citrullinated proteins gives the first clues to the etiology of rheumatoid arthritis

Rheumatoid arthritis (RA) is now clearly a true autoimmune disease with accumulating evidence of pathogenic disease-specific autoimmunity to citrullinated proteins. Citrullination, also termed deimination, is a modification of arginine side chains catalyzed by peptidylarginine deiminase (PAD) enzymes. This post-translational modification has the potential to alter the structure, antigenicity, and function of proteins. In RA, antibodies to cyclic citrullinated peptides are now well established for clinical diagnosis, though we argue that the identification of specific citrullinated antigens, as whole proteins, is necessary for exploring pathogenic mechanisms. Four citrullinated antigens, fibrinogen, vimentin, collagen type II, and alpha-enolase, are now well established, with others awaiting further characterization. All four proteins are expressed in the joint, and there is evidence that antibodies to citrullinated fibrinogen and collagen type II mediate inflammation by the formation of immune complexes, both in humans and animal models. Antibodies to citrullinated proteins are associated with HLA 'shared epitope' alleles, and autoimmunity to at least one antigenic sequence, the CEP-1 peptide from citrullinated alpha-enolase (KIHAcitEIFDScitGNPTVE), shows a specific association with HLA-DRB1*0401, *0404, 620W PTPN22, and smoking. Periodontitis, in which Porphyromonas gingivalis is a major pathogenic bacterium, has been linked to RA in epidemiological studies and also shares similar gene/environment associations. This is also the only bacterium identified that expresses endogenous citrullinated proteins and its own bacterial PAD enzyme, though the precise molecular mechanisms of bacterial citrullination have yet to be explored. Thus, both smoking and Porphyromonas gingivalis are attractive etiological agents for further investigation into the gene/environment/autoimmunity triad of RA.

The danger model in deciphering autoimmunity

Autoimmunity has been a topic of intensive research for several decades, yet amazingly, no uniform hypothesis exists to explain the basis for the spectrum of autoantibody specificities seen in autoimmune diseases. It therefore seems appropriate to consider whether our current framework for understanding tolerance, and thus the mechanisms controlling the initiation and perpetuation of autoimmunity, may be faulty. Adapting the paradigm of Matzinger-the 'danger model', a case can be made for a perspective that appreciates the fundamental role of the tissues in controlling immune response, favouring a shift of focus in studies on the initiation of autoimmunity. Applying the elements of this model, I set forth a number of scenarios for how autoreactivity could emerge, with emphasis on the likely sources of the involved autoantigens and the functional basis of their appearance. The emerging picture is one in which disruption of tissue homeostasis takes centre stage, with the antigen-presenting cells as the key players.

Human leukocyte antigen association in idiopathic thrombotic thrombocytopenic purpura: evidence for an immunogenetic link

BACKGROUND

Thrombotic thrombocytopenic purpura (TTP) is a rare, acute, life-threatening disorder, associated with a deficiency in ADAMTS 13. The majority of acute, idiopathic, adult TTP cases are associated with anti-ADAMTS 13 IgG antibodies. However, the factor(s) precipitating an acute TTP episode are not always obvious; indeed, a multifactorial etiology is likely.

OBJECTIVES AND METHODS

DNA was used for human leukocyte antigen (HLA) class II typing, using polymerase chain reaction (PCR)-sequence-specific primer and PCR-sequence-specific oligonucleotide probe to methodology to investigate 50 European acquired idiopathic TTP cases.

RESULTS

There was an increase in the frequency of HLA-DQB1*0301 (HLA-DQ7) in patients with TTP as compared with controls [58.0% vs. 34.5% (P=0.048)]. The frequencies of HLA-DRB1*11 and HLA-DRB3* were also significantly increased in TTP patients as compared with controls [44.0% vs. 12.0% (P=0.0024) and 84.0% vs. 58.0% (P=0.024)], although it remains uncertain whether susceptibility is influenced by HLA-DQ or HLA-DR molecules or other genes in this haplotype. The frequencies of HLA-DRB1*04 and HLA-DRB4 (HLA-DR53) were significantly decreased in the patient group as compared with controls [10.0% vs. 35.0% and 26.0% vs. 61.5% (P=0.0096 and P=0.0024, respectively)], and may have a protective effect against the development of TTP.

CONCLUSION

Analysis identified HLA class II types associated with susceptibility to and a protective effect against the development of acute acquired TTP in European patients. This provides the first description of a genetic factor predicting the risk of developing acquired antibody-mediated TTP.

Association of TNF-alpha gene polymorphisms with systemic lupus erythematosus in Taiwanese patients

Tumour necrosis factor-alpha (TNF-alpha), an important proinflammatory cytokine, exerts a variety of physiological and pathogenic effects that lead to tissue destruction. Studies on the association of TNF-alpha genetic polymorphisms with systemic lupus erythematosus (SLE) have yielded inconclusive results. We investigated the association of TNF-alpha genetic polymorphisms (-1031T/C, -863C/A, -857T/C, -308A/G and +489A/G) with SLE in Taiwanese patients and controls. Our results indicate that 1) the frequency of the A-allele at -863 position was significantly higher in SLE patients (odds ratio = 1.46; 95% CI = 1.02-2.08); 2) the frequency of the A-allele at +489 position was significantly higher in SLE patients (odds ratio = 1.79; 95% CI = 1.21-2.65); 3) the AA or GA genotype frequencies at +489 position were significantly increased in SLE patients (AA genotype: odds ratio = 11.20; 95% CI = 1.36-92.55; GA genotype: odds ratio = 1.63; 95% CI = 1.03-2.58); 4) no significant association of TNF-alpha haplotypic distributions was observed, except for the haplotypes TCCGA, CACGA and CCCGG; and 5) the genotype frequency of the polymorphisms at -1031 was significantly different in patients with antinuclear antibodies (P = 0.022). The allele and genotype frequencies of the polymorphisms at -863 were not significantly different. The genotype frequency of the polymorphisms at -857 was significantly different in patients with haematological disorder (P = 0.025). The frequency of A allele of the polymorphisms at -308 was significantly increased in patients with malar rash (P = 0.033), discoid rash (P = 0.023), photosensitivity (P = 0.037), oral ulcers (P = 0.002) and serositis (P = 0.029). The genotype frequency of the polymorphisms at +489 was significantly different in patients with discoid rash and photosensitivity (data not shown; discoid rash, P = 0.031; photosensitivity, P = 0.044). These results suggest that TNF-alpha genetic polymorphisms contribute to SLE susceptibility in the Taiwanese population.

Linkage analysis of the C4A/C4B copy number variation and polymorphisms of the adjacent steroid 21-hydroxylase gene in a healthy population

Genes encoding the steroid 21-hydroxylase (CYP21A2) and the complement component C4 proteins (C4A and C4B) are located in the MHC region in a strongly linked structure named RCCX module. Previous studies found that carriers of C4B gene deficiency (C4B*Q0) have higher risk for cardiovascular diseases. A potential explanation is that lacking the C4B gene may result in altered function of the neighboring CYP21A2 gene. Therefore we sequenced the CYP21A2 gene in 96 healthy individuals to identify polymorphisms and to characterize their linkage pattern. Fifty-three variations were detected including a new one which alters the TATA-box of the gene. Only three known mutations (V281L, Q318X and R479L) associated with congenital adrenal hyperplasia, were found in 7, 2 and 1 subjects, respectively. Linkage analysis revealed that some variations exhibit strong correlation with the C4 copy number polymorphism and constituents of the MHC III region. Rare alleles of three polymorphisms were identified as components of the 8.1 ancestral haplotype. Haplotyping and family study confirmed that the variant alleles of two intronic SNPs were constituents of haplotype blocks lacking the C4B gene. These results suggest that variations of CYP21A2 gene can be involved in disease associations of the 8.1 haplotype and the C4B*Q0 genotype.

Identification of two independent risk factors for lupus within the MHC in United Kingdom families

The association of the major histocompatibility complex (MHC) with SLE is well established yet the causal variants arising from this region remain to be identified, largely due to inadequate study design and the strong linkage disequilibrium demonstrated by genes across this locus. The majority of studies thus far have identified strong association with classical class II alleles, in particular HLA-DRB1*0301 and HLA-DRB1*1501. Additional associations have been reported with class III alleles; specifically, complement C4 null alleles and a tumor necrosis factor promoter SNP (TNF-308G/A). However, the relative effects of these class II and class III variants have not been determined. We have thus used a family-based approach to map association signals across the MHC class II and class III regions in a cohort of 314 complete United Kingdom Caucasian SLE trios by typing tagging SNPs together with classical typing of the HLA-DRB1 locus. Using TDT and conditional regression analyses, we have demonstrated the presence of two distinct and independent association signals in SLE: HLA-DRB1*0301 (nominal p = 4.9 × 10⁻⁸, permuted p < 0.0001, OR = 2.3) and the T allele of SNP rs419788 (nominal p = 4.3 × 10⁻⁸, permuted p < 0.0001, OR = 2.0) in intron 6 of the class III region gene SKIV2L. Assessment of genotypic risk demonstrates a likely dominant model of inheritance for HLA-DRB1*0301, while rs419788-T confers susceptibility in an additive manner. Furthermore, by comparing transmitted and untransmitted parental chromosomes, we have delimited our class II signal to a 180 kb region encompassing the alleles HLA-DRB1*0301-HLA-DQA1*0501-HLA-DQB1*0201 alone. Our class III signal importantly excludes independent association at the TNF promoter polymorphism, TNF-308G/A, in our SLE cohort and provides a potentially novel locus for future genetic and functional studies.

Systemic lupus erythematosus (SLE/lupus) is a complex autoimmune disease in which the body's immune system attacks its own tissues, causing inflammation in a variety of different organs such as the skin, joints, and kidneys. The cause of lupus is not known, but genes play a significant role in the predisposition to disease. The major histocompatibility complex (MHC) on Chromosome 6 contains at least 100 different genes that affect the immune system, including the genes with the strongest effect on lupus susceptibility. Despite the importance of the MHC in SLE, the identity of the actual genes in the MHC region that cause SLE has remained elusive. In the present study, we used the latest set of genetic markers present at the MHC in lupus families to identify the actual genes that affect the disease. To our knowledge, we have shown for the first time that two separate groups of genes are involved in SLE. One group of genes alters how the immune system may inappropriately target its own tissues in the disease. How the second set of genes predisposes to SLE is the subject of ongoing study.

Polymorphisms of TNF-alpha and LT-alpha genes in multiple myeloma

Allelic distribution of -308 G>A (TNF 1/2) polymorphism of the TNF-alpha, and the +252 A>G promoter polymorphism of the LT-alpha gene, the 1267 A>G polymorphism of the HSP70-2 gene as well as the -429 T>C promoter polymorphism of the RAGE gene were tested in 94 MM cases and 141 controls. Significantly less MM patients than controls carried the TNF2 allele (p=0.018) and the TNF2-LTA 252G haplotype (p=0.025). The difference was, however, restricted to the females, as well as the relatively young (<69 years) subjects. By contrast, we did not find differences with the other SNPs tested.

The 8.1 ancestral MHC haplotype is strongly associated with colorectal cancer risk

Many recent data indicate that some alleles encoded in the central major histocompatibility complex (MHC) region (Class III) of short arm of chromosome 6 may modify the risk of cancer development. Therefore we determined 4 single nucleotide polymorphisms (SNPs) of this region (TNF-alpha -308 G > A, RAGE -429 T > C, HSP70-2 -1267 A > G, LTA 252 A > G) in genomic DNA samples from 183 Hungarian patients with colorectal cancer and 141 age matched control subjects representing the Hungarian population of the same age and gender. No significant differences were found in either SNP tested. When, however, three- or four-locus haplotypes consisting of known constituents of the so-called 8.1 ancestral haplotype (8.1AH) were considered, marked differences were observed. Frequency of TNF-alpha -308A, RAGE -429C, HSP70-2 -1267G, LTA 252G (8.1AH) haplotype was significantly (p = 0.006) more frequent (19.1%) among patients than in the controls (7.7%). Age- and gender-adjusted ratio of the 8.1AH carriers vs. non-carriers to have colorectal cancer was 2.514 (1.130-5.594). This risk was higher in <or=67 years old subjects (4.073 (1.317-12.596)) and in females (3.771 (1.302-10.927). These findings-consistent with similar recent results with ovarian cancer-indicate that carriers of the 8.1AH, encoding for an altered immune response and known to be associated with alterations of several immune functions and autoimmune diseases have an increased risk for some cancer types. These findings may contribute to better understanding how the defense mechanisms against tumors could be enhanced/strengthened.

Association between early onset and organ manifestations of systemic lupus erythematosus (SLE) and a down-regulating promoter polymorphism in the MBL2 gene

The serum concentration of mannose-binding lectin (MBL) is genetically determined by a series of allelic polymorphisms in the MBL2 gene. Since several polymorphisms of the MBL2 gene have been suggested to be risk locus for systemic lupus erythematosus (SLE), we investigated MBL2 polymorphisms in 315 SLE patients from Hungary and 182 geographically matched healthy controls. Within the group of patients, we found that homozygotes for an MBL2 down-regulating promoter polymorphism at position -221 (YA to XA) (rs7096206) were significantly (p=0.017) younger at diagnosis than the other patients. The frequency of juvenile-onset SLE (<or=20 years) was particularly high among XA/XA homozygotes (17.4%) as compared to the rest of the patients (5.6%) (p=0.004). XA/XA carriers did have significantly higher risk of development of cutaneous manifestations (p=0.003) and pleuritis/pericarditis (p=0.013) as compared with the rest of the patients. These data indicate that MBL may act as a disease modifier in SLE patients through a mechanism to be identified.

Differential tissue targeting of autoimmunity manifestations by autoantigen-associated Y RNAs

OBJECTIVE

To assess the Y RNAs, a family of homologous RNAs that bind to the Ro autoantigen, for the ability to contribute to autoimmune disease by activating RNA-responsive Toll-like receptors (TLRs).

METHODS

Using cell lines expressing or stably transfected with TLR-3, TLR-7, or TLR-8, we determined the patterns of RNA-specific TLR activation by in vitro transcripts of all of the known murine and human Y RNAs. Next, 8-10-week-old female mice were exposed to a single 50-microg subcutaneous injection of mouse Y1 or mouse Y3 RNA, and the effects were observed.

RESULTS

Y RNA family members differed in their TLR reactivities. Both human and mouse Y3 RNAs, but not other human or mouse Y RNAs, prominently induced TLR-3 activation. Although most human and mouse Y RNAs activated TLR-7 efficiently, mouse Y3 RNA and human Y5 RNA did not. Single subcutaneous injections of mice with either mouse Y1 RNA or mouse Y3 RNA induced or inhibited lymphoid infiltrates in different target organs based on the Y RNA and TLR status of the mouse used. Mouse Y1 RNA induced kidney lesions in TLR-3-intact mice but not in TLR-3-knockout mice. In contrast, mouse Y3 RNA treatment was associated with nephritis in TLR-3-knockout mice but not in TLR-3-intact mice. Sialoadenitis developed in untreated TLR-3-/- mice and in TLR-3-/- mice treated with mouse Y3 RNA, but sialoadenitis was not present in TLR--/-) mice treated with mouse Y1 RNA.

CONCLUSION

Y RNAs can induce innate immune responses and influence clinical manifestations of autoimmunity, suggesting that they are relevant to syndromes of anti-Ro autoimmunity. Distinct patterns of tissue targeting can be seen after exposure to different Y RNAs, in a pattern that correlates with the innate immune signals they induce. Thus, the balance of innate immune signals induced by exposure to endogenous Y RNAs may help determine the nature of the clinical syndrome in anti-Ro autoimmunity.

Unraveling the genetics of systemic lupus erythematosus

The capacity to locate polymorphisms on a virtually complete map of the human genome coupled with the ability to accurately evaluate large numbers (by historical standards) of genetic markers has led to gene identification in complex diseases, such as systemic lupus erythematosus (SLE or lupus). While this is a phenotype with enormous clinical variation, the twin studies and the observed familial aggregation, along with the genetic effects now known, suggest a strong genetic component. Unlike type 1 diabetes, lupus genetics is not dominated by the powerful effect of a single locus. Instead, there are at least six known genetic association effects in lupus of smaller magnitude (odds ratio <2), and at least 17 robust linkages (established and arguably confirmed independently) defining potentially responsible genes that largely remain to be discovered. The more convincing genetic associations include the human leukocyte antigen region (with multiple genes), C1q, PTPN22, PDCD1, Fc receptor-like 3, FcgammaRIIA, FcgammaRIIIA, interferon regulatory factor 5, and others. How they contribute to disease risk remains yet to be clarified, beyond the obvious speculation derived from what has previously been learned about these genes. Certainly, they are expected to contribute to lupus risk independently and in combination with each other, with genes not yet identified, and with the environment. A substantial number of genes (>10) are expected to be identified to contribute to lupus or in its many subsets defined by clinical and laboratory features.