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- Kissel, T, et al.
(författare)
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Surface Ig variable domain glycosylation affects autoantigen binding and acts as threshold for human autoreactive B cell activation
- 2022
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Ingår i: Science advances. - : American Association for the Advancement of Science (AAAS). - 2375-2548. ; 8:6, s. eabm1759-
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Tidskriftsartikel (refereegranskat)abstract
- The hallmark autoantibodies in rheumatoid arthritis are characterized by variable domain glycans (VDGs). Their abundant occurrence results from the selective introduction of N-linked glycosylation sites during somatic hypermutation, and their presence is predictive for disease development. However, the functional consequences of VDGs on autoreactive B cells remain elusive. Combining crystallography, glycobiology, and functional B cell assays allowed us to dissect key characteristics of VDGs on human B cell biology. Crystal structures showed that VDGs are positioned in the vicinity of the antigen-binding pocket, and dynamic modeling combined with binding assays elucidated their impact on binding. We found that VDG-expressing B cell receptors stay longer on the B cell surface and that VDGs enhance B cell activation. These results provide a rationale on how the acquisition of VDGs might contribute to the breach of tolerance of autoreactive B cells in a major human autoimmune disease.
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- Notarnicola, A., et al.
(författare)
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Autoantibodies against a subunit of mitochondrial respiratory chain complex I in inclusion body myositis
- 2023
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Ingår i: Annals of the Rheumatic Diseases. - : BMJ. - 0003-4967 .- 1468-2060. ; 82, s. 574-574
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Tidskriftsartikel (refereegranskat)abstract
- Background Autoantibodies are found in up to 80% of patients with idiopathic inflammatory myopathies (IIM) and are associated with distinct clinical phenotypes [1]. Autoantibodies targeting cytosolic 5´-nucleotidase 1A (anti-cN1A) are currently the only known serum biomarker for the subgroup inclusion body myositis (IBM) (2), although detected even in other autoimmune diseases.Objectives To identify new autoimmune targets in IIM by antigen bead array assay.Methods In a first cross-sectional exploratory study, 357 antigens representing 268 proteins were incubated with plasma samples from 219 IIM (108 Polymyositis (PM), 80 Dermatomyositis (DM) and 31 IBM) patients, 349 Systemic Lupus Erythematosus (SLE) patients and 306 population controls for screening of IgG reactivity by antigen bead array. All samples were identified in the local biobank of the Rheumatology clinic, Karolinska University Hospital. Interesting results obtained for the IBM subgroup were then validated in an independent larger cohort of 287 patients with IBM followed at nine European rheumatological or neurological centers. IBM serum samples were explored by antigen bead array and results validated by western blot. As controls, serum samples from 30 patients with PM and 30 with DM, HLA-matched with the IBM Swedish cohort, were included. Demographics, laboratory, clinical, and muscle biopsy data of the IBM cohort was retrieved.Results In the exploratory study IgG reactivity towards NADH dehydrogenase 1 α subcomplex 11 (NDUFA11), a subunit of the membrane-bound mitochondrial respiratory chain complex I, was discovered with higher frequency in the IBM (9,7%) than PM (2,8%) and DM samples (2,5%), although the difference was not statistically significant. Anti-NDUFA11 IgG was also found in 2,3% of SLE and 2,6% of population control samples. In the validation study anti-NDUFA11 autoantibodies were detected in 11/287 IBM patients (3,8%), 0/30 PM and 0/30 DM patients. Reactivity against NDUFA11 could be confirmed by western blot (Table 1, Figure 1). The eleven anti-NDUFA11 positive patients showed a trend of lower frequency of wheelchair/walker ever use and higher creatine kinase levels at time of IBM diagnosis compared to the anti-NDUFA11 negative group. Ragged red fibers were significantly more prevalent in anti-NDUFA11 positive than negative patients (p=0.04). Anti-cN1A autoantibodies were detected in 98/287 (34,1%) of IBM, 3/30 (10%) DM and 9/29 (31%) PM patients, p=0.03. Coexistence of anti NDUFA11 and anti-cN1A antibodies was observed in 3 IBM patients.Conclusion Our results reveal a new autoimmune target in the mitochondrial respiratory chain complex I that might be specifically associated with IBM. This is of particular interest as mitochondrial abnormalities are known histological findings in muscle biopsies of IBM patients.References [1]Galindo-Feria AS, Wang G, Lundberg IE. Autoantibodies: Pathogenic or epiphenomenon. Best Pract Res Clin Rheumatol. 2022;36(2):101767.[2]Herbert MK,et al. Disease specificity of autoantibodies to cytosolic 5’-nucleotidase 1A in sporadic inclusion body myositis versus known autoimmune diseases. Ann Rheum Dis. 2016;75(4):696-701.
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- Seidl, Rainer, et al.
(författare)
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Deficient brain snRNP70K in patients with Down syndrome
- 2001
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Ingår i: Electrophoresis. - : Wiley-VCH Verlagsgesellschaft. - 0173-0835 .- 1522-2683. ; 22:1, s. 43-48
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Tidskriftsartikel (refereegranskat)abstract
- The small nuclear ribonucleoprotein 70K (snRNP 70K; U1-70 kDa) is an integral part of the spliceosome, a large RNA-protein complex catalyzing the removal of introns from nuclear pre-mRNA. snRNP is one of the best-studied essential subunits of snRNPs, is highly conserved and its inactivation was shown to result in complete inhibition of splicing. Applying subtractive hybridization, we found a sequence with 100% identity to snRNP absent in fetal Down syndrome (DS) brain. This observation made us determine snRNP-mRNA steady-state levels and protein levels in brains of adult patients with DS. snRNP-mRNA and protein levels of five individual brain regions of DS and controls each, were determined by blotting techniques. snRNP-mRNA steady state levels were significantly decreased in DS brain. Performing Western blots with monoclonal and human antibodies, snRNP protein levels were decreased in several regions of DS brain, although one monoclonal antibody did not reveal different snRNP-immunoreactivity. Although decreased snRNP-protein could be explained by decreased mRNA-steady state levels, another underlying mechanism might be suggested: snRNP is one of the death substrates rapidly cleaved during apoptosis by interleukin-1-beta-converting enzyme-like (ICE) proteases, which was well-documented by several groups. As apoptosis is unrequivocally taking place in DS brain leading to permanent cell loses, decreased snRNP-protein levels may therefore reflect decreased synthesis and increased apoptosis-related proteolytic cleavage.
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