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- Langefeld, Carl D., et al.
(author)
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Transancestral mapping and genetic load in systemic lupus erythematosus
- 2017
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In: Nature Communications. - : NATURE PUBLISHING GROUP. - 2041-1723. ; 8
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Journal article (peer-reviewed)abstract
- Systemic lupus erythematosus (SLE) is an autoimmune disease with marked gender and ethnic disparities. We report a large transancestral association study of SLE using Immunochip genotype data from 27,574 individuals of European (EA), African (AA) and Hispanic Amerindian (HA) ancestry. We identify 58 distinct non-HLA regions in EA, 9 in AA and 16 in HA (similar to 50% of these regions have multiple independent associations); these include 24 novel SLE regions (P < 5 x 10(-8)), refined association signals in established regions, extended associations to additional ancestries, and a disentangled complex HLA multigenic effect. The risk allele count (genetic load) exhibits an accelerating pattern of SLE risk, leading us to posit a cumulative hit hypothesis for autoimmune disease. Comparing results across the three ancestries identifies both ancestry-dependent and ancestry-independent contributions to SLE risk. Our results are consistent with the unique and complex histories of the populations sampled, and collectively help clarify the genetic architecture and ethnic disparities in SLE.
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- Horwood, Joshua T. M., et al.
(author)
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FLOW INSTABILITIES IN GAS TURBINE CHUTE SEALS
- 2019
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In: PROCEEDINGS OF THE ASME TURBO EXPO. - : ASME Press.
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Conference paper (peer-reviewed)abstract
- The ingress of hot annulus gas into stator-rotor cavities is an important topic to engine designers. Rim-seals reduce the pressurised purge required to protect highly-stressed components. This paper describes an experimental and computational study of flow through a turbine chute seal. The computations which include a 360 degrees domain - were undertaken using DLR TRACE's time-marching solver. The experiments used a low Reynolds number turbine rig operating with an engine-representative flow structure. The simulations provide an excellent prediction of cavity pressure and swirl, and good overall agreement of sealing effectiveness when compared to experiment. Computation of flow within the chute seal showed strong shear gradients which influence the pressure distribution and secondary-flow field near the blade leading edge. High levels of shear across the rim-seal promote the formation of large-scale structures at the wheel-space periphery; the number and speed of which were measured experimentally and captured, qualitatively and quantitatively, by computations. A comparison of computational domains ranging from 30 degrees to 360 degrees indicate that steady features of the flow are largely unaffected by sector size. However, differences in large-scale flow structures were pronounced with a 60 degrees sector and suggest that modelling an even number of blades in small sector simulations should be avoided.
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- Kim, Kwangwoo, et al.
(author)
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High-density genotyping of immune loci in Koreans and Europeans identifies eight new rheumatoid arthritis risk loci
- 2015
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In: Annals of the Rheumatic Diseases. - : BMJ. - 0003-4967 .- 1468-2060. ; 74:3
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Journal article (peer-reviewed)abstract
- Objective A highly polygenic aetiology and high degree of allele-sharing between ancestries have been well elucidated in genetic studies of rheumatoid arthritis. Recently, the high-density genotyping array Immunochip for immune disease loci identified 14 new rheumatoid arthritis risk loci among individuals of European ancestry. Here, we aimed to identify new rheumatoid arthritis risk loci using Korean-specific Immunochip data. Methods We analysed Korean rheumatoid arthritis case-control samples using the Immunochip and genome-wide association studies (GWAS) array to search for new risk alleles of rheumatoid arthritis with anticitrullinated peptide antibodies. To increase power, we performed a meta-analysis of Korean data with previously published European Immunochip and GWAS data for a total sample size of 9299 Korean and 45 790 European case-control samples. Results We identified eight new rheumatoid arthritis susceptibility loci (TNFSF4, LBH, EOMES, ETS1-FLI1, COG6, RAD51B, UBASH3A and SYNGR1) that passed a genome-wide significance threshold (p<5x10(-8)), with evidence for three independent risk alleles at 1q25/TNFSF4. The risk alleles from the seven new loci except for the TNFSF4 locus (monomorphic in Koreans), together with risk alleles from previously established RA risk loci, exhibited a high correlation of effect sizes between ancestries. Further, we refined the number of single nucleotide polymorphisms (SNPs) that represent potentially causal variants through a trans-ethnic comparison of densely genotyped SNPs. Conclusions This study demonstrates the advantage of dense-mapping and trans-ancestral analysis for identification of potentially causal SNPs. In addition, our findings support the importance of T cells in the pathogenesis and the fact of frequent overlap of risk loci among diverse autoimmune diseases.
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- Lenz, Tobias L., et al.
(author)
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Widespread non-additive and interaction effects within HLA loci modulate the risk of autoimmune diseases
- 2015
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In: Nature Genetics. - : Macmillan Publishers Ltd.. - 1061-4036 .- 1546-1718. ; 47:9, s. 1085-1090
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Journal article (peer-reviewed)abstract
- Human leukocyte antigen (HLA) genes confer substantial risk for autoimmune diseases on a log-additive scale. Here we speculated that differences in autoantigen-binding repertoires between a heterozygote's two expressed HLA variants might result in additional non-additive risk effects. We tested the non-additive disease contributions of classical HLA alleles in patients and matched controls for five common autoimmune diseases: rheumatoid arthritis (n(cases) = 5,337), type 1 diabetes (T1D; n(cases) = 5,567), psoriasis vulgaris (n(cases) = 3,089), idiopathic achalasia (n(cases) = 727) and celiac disease (ncases = 11,115). In four of the five diseases, we observed highly significant, non-additive dominance effects (rheumatoid arthritis, P = 2.5 x 10(-12); T1D, P = 2.4 x 10(-10); psoriasis, P = 5.9 x 10(-6); celiac disease, P = 1.2 x 10(-87)). In three of these diseases, the non-additive dominance effects were explained by interactions between specific classical HLA alleles (rheumatoid arthritis, P = 1.8 x 10(-3); T1D, P = 8.6 x 10(-27); celiac disease, P = 6.0 x 10(-100)). These interactions generally increased disease risk and explained moderate but significant fractions of phenotypic variance (rheumatoid arthritis, 1.4%; T1D, 4.0%; celiac disease, 4.1%) beyond a simple additive model.
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- Sævik, Åse Bjorvatn, et al.
(author)
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Clues for early detection of autoimmune Addison's disease : myths and realities
- 2018
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In: Journal of Internal Medicine. - : Wiley-Blackwell Publishing Inc.. - 0954-6820 .- 1365-2796. ; 283:2, s. 190-199
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Journal article (peer-reviewed)abstract
- Background: Early detection of autoimmune Addison's disease (AAD) is important as delay in diagnosis may result in a life-threatening adrenal crisis and death. The classical clinical picture of untreated AAD is well-described, but methodical investigations are scarce.Objective: Perform a retrospective audit of patient records with the aim of identifying biochemical markers for early diagnosis of AAD.Material and methods: A multicentre retrospective study including 272 patients diagnosed with AAD at hospitals in Norway and Sweden during 1978-2016. Scrutiny of medical records provided patient data and laboratory values.Results: Low sodium occurred in 207 of 247 (84%), but only one-third had elevated potassium. Other common nonendocrine tests were largely normal. TSH was elevated in 79 of 153 patients, and hypoglycaemia was found in 10%. Thirty-three per cent were diagnosed subsequent to adrenal crisis, in whom electrolyte disturbances were significantly more pronounced (P < 0.001). Serum cortisol was consistently decreased (median 62 nmol L-1 [1-668]) and significantly lower in individuals with adrenal crisis (38 nmol L-1 [2-442]) than in those without (81 nmol L-1 [1-668], P < 0.001).Conclusion: The most consistent biochemical finding of untreated AAD was low sodium independent of the degree of glucocorticoid deficiency. Half of the patients had elevated TSH levels. Only a minority presented with marked hyperkalaemia or other nonhormonal abnormalities. Thus, unexplained low sodium and/or elevated TSH should prompt consideration of an undiagnosed AAD, and on clinical suspicion bring about assay of cortisol and ACTH. Presence of 21-hydroxylase autoantibodies confirms autoimmune aetiology. Anticipating additional abnormalities in routine blood tests may delay diagnosis.
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- van Steenbergen, H. W., et al.
(author)
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Association of valine and leucine at HLA-DRB1 position 11 with radiographic progression in rheumatoid arthritis, independent of the shared epitope alleles but not independent of anti-citrullinated protein antibodies
- 2015
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In: Arthritis & Rheumatology. - : Wiley. - 2326-5191 .- 2326-5205. ; 67:4, s. 877-886
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Journal article (peer-reviewed)abstract
- OBJECTIVE: For decades it has been known that the HLA-DRB1 shared epitope (SE) alleles are associated with an increased risk of development and progression of rheumatoid arthritis (RA). Recently, the following variations in the peptide-binding grooves of HLA molecules that predispose to RA development have been identified: Val and Leu at HLA-DRB1 position 11, Asp at HLA-B position 9, and Phe at HLA-DPB1 position 9. This study was undertaken to investigate whether these variants are also associated with radiographic progression in RA, independent of SE and anti-citrullinated protein antibody (ACPA) status.METHODS: A total of 4,911 radiograph sets from 1,878 RA patients included in the Leiden Early Arthritis Clinic (The Netherlands), Umeå (Sweden), Hospital Clinico San Carlos-Rheumatoid Arthritis (Spain), and National Data Bank for Rheumatic Diseases (US) cohorts were studied. HLA was imputed using single-nucleotide polymorphism data from an Immunochip, and the amino acids listed above were tested in relation to radiographic progression per cohort using an additive model. Results from the 4 cohorts were combined in inverse-variance weighted meta-analyses using a fixed-effects model. Analyses were conditioned on SE and ACPA status.RESULTS: Val and Leu at HLA-DRB1 position 11 were associated with more radiographic progression (meta-analysis P = 5.11 × 10(-7)); this effect was independent of SE status (meta-analysis P = 0.022) but not independent of ACPA status. Phe at HLA-DPB1 position 9 was associated with more severe radiographic progression (meta-analysis P = 0.024), though not independent of SE status. Asp at HLA-B position 9 was not associated with radiographic progression.CONCLUSION: Val and Leu at HLA-DRB1 position 11 conferred a risk of a higher rate of radiographic progression independent of SE status but not independent of ACPA status. These findings support the relevance of these amino acids at position 11.
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