Biology subjects

Lundberg, I. E.

Publications and source records attributed to Lundberg, I. E..

6 recordsLinked to original sources

bioRxiv2026

The metabolic profile of Extracellular Vesicles identifies and separates patients with Sarcoidosis and Anti-Synthetase Syndrome

Sarcoidosis is a multisystem disorder that primarily affects the lungs and is characterizedby granulomatous inflammation. However, much of the underlying disease mechanisms remain poorly understood. Extracellular vesicles (EVs) are small membrane-bound particles released by all cells and carry various cargos including metabolites. They are involved in intercellular communication that can be dysregulated in diseases.This study characterizes the metabolic cargo of EVs isolated from bronchoalveolar lavage fluid (BALF), using liquid chromatography-mass spectrometry (LC-MS)-based metabolomic analysis, in patients with sarcoidosis (n=37), compared to healthy controls (n=10). Additionally, the sarcoidosis signature was compared to another pulmonary disorder, anti-synthetase syndrome (ASyS, n=10). Arachidonic acid (AA) results were verified by ELISA. A total of 1202 metabolites were detected, with 111 annotated ones further analyzed. EVs from sarcoidosis patients showed distinct metabolomic profiles compared to both ASyS patients and healthy controls, with 38 annotated metabolites differentially expressed in any of the groups. In both annotated and non-annotated data, sarcoidosis patients clustered separately from ASyS patients and healthy individuals. Furthermore, sarcoidosis patients clustered in 3 subgroups, whereof one was similar to ASyS patients and one stood out as showing higher cell counts in BALF. Higher AA levels were found in sarcoidosis patient EVs by LC-MS, and AA results were verified by ELISA. Our data show that BALF EV metabolites are disease-dependent and support the notion thatsarcoidosis patients should be further subgrouped for better diagnosis and treatment.

immunology↗

bioRxiv2026

MDA5 multimerization on LINE RNA drives pathogenic extracellular immune complexes in autoimmunity

Autoantibodies are hallmarks of many autoimmune diseases, but their potential pathogenic roles, particularly for those targeting intracellular proteins, remain unclear. Anti-MDA5-positive dermatomyositis (anti-MDA5 DM) is characterized by autoantibodies against the intracellular protein MDA51,2, a conserved innate immune receptor that recognizes viral dsRNA by forming filaments3. Here, using four patient-derived monoclonal autoantibodies (mAbs), we reconstitute and define the molecular architecture, biogenesis, and immunological activity of pathogenic MDA5 immune complexes. Our cryo-EM analysis revealed that these mAbs bind dsRNA-scaffolded MDA5 filaments in at least two distinct binding modes, each exhibiting striking epitope convergence using germline-encoded residues. Extracellular immune complexes formed between mAbs and filamentous, but not monomeric, MDA5 potently activate multiple innate immune pathways, with the magnitude of activation determined by antibody binding mode and immune complex stoichiometry. Antibody bivalency further crosslinks MDA5 filaments into higher-order aggregates with heightened immunostimulatory activity, demonstrating an active role of autoantibodies in shaping immune complex architecture. Analysis of patient plasma reveals elevated levels of extracellular MDA5 filaments and identifies LINE retroelement-derived dsRNA as a structural scaffold. Notably, MDA5 immune complexes induce endogenous LINE dsRNA expression, likely promoting additional MDA5 filament formation and extracellular release through inflammatory cell death. These data thus support a self-amplifying inflammatory cycle as a pathogenic mechanism for anti-MDA5 DM. Collectively, our study defines a broadly applicable architectural principle, in which higher-order organization and binding modes of autoantibodies--beyond antibody affinity or nucleic acid presence alone--govern innate immune activation.

biochemistry↗

bioRxiv2025

Anti-MDA5 monoclonal antibodies from patients with dermatomyositis - B cell characteristics and differential targeting of the helicase domains

ObjectivesAutoantibodies targeting melanoma differentiation associated protein 5 (MDA5) are strongly associated with dermatomyositis (DM) and may contribute to its pathogenesis. Here we aimed to investigate MDA5+ B cells, their phenotype and generate MDA5 monoclonal antibodies to assess their epitope specificity. MethodsMDA5-reactive B cells were captured from peripheral blood of patients with anti-MDA5+ DM (n=3) using an MDA5-fluorescent probe. B cell receptor (BCR) sequences were analysed from single-sorted B cells (n=240). Selected clones were re-expressed as IgG1 monoclonal antibodies (mAbs, n=23). Reactivity was assessed using recombinant MDA5 protein constructs, peptide epitope mapping, ELISA, western blot and a commercial line blot assay. ResultsOf 240 anti-MDA5+ sorted B cells, 23 BCRs were re-expressed as mAbs, two of which showed high reactivity and specificity for MDA5. These antibody sequences originated from one CD19+IgD-CD27-CD38+ and one CD19+IgD-CD27+CD38+ IgG+ B cell with low somatic hypermutation (SHM). Both mAbs had nanomolar apparent affinity and bound to sites within the helicase domains of the MDA5 protein but with distinct epitope recognition. Serology screening confirmed targeting of a linear epitope identified in the mAb studies. ConclusionOur results show that anti-MDA5+ B cells recognize the helicase domains, which are the enzymatically active domains of the protein. These results have implications for understanding the etiopathology of anti-MDA5+ DM and development of new antigen-specific therapies.

immunology↗

bioRxiv2024

Serum from patients with Idiopathic inflammatory myopathy induces skeletal muscle weakness

Idiopathic inflammatory myopathies (IIM) are a group of systemic autoimmune inflammatory disorders that primarily affect striated muscles leading to weakness and accelerated fatigue. The disseminated muscle phenotype points to systemic humoral factors as mediators of the disease. Autoantibodies are important biomarkers for disease classification; it is not known if they play a direct role in IIM disease development. This study aims to investigate if IIM patient serum or isolated IgG could directly impair contractile function in muscle. Isolated flexor digitorum brevis (FDB) muscles from healthy mice were exposed to serum (10-50%) from healthy controls or patients with recent onset IIM. Some muscles were exposed to isolated total IgG (50 or 150g/ml) from patients with IIM. Muscle force in whole muscles was measured before and after exposure to sera or IgG. Muscle force and intracellular [Ca2+] in single muscle fibers were measured after exposure to serum. FDB muscles exposed to serum from patients with IIM displayed a marked reduction in force production in both 10% and 50% serum. Moreover, single myofibers dissected from FDB muscles exposed to IIM sera displayed lower force but unaffected Ca2+ release during contractions, which indicates myofibrillar dysfunction, but not intracellular Ca2+ release, as the cause to weakness. FDB muscles exposed to total IgG from IIM patients did not display any reduction in muscle force. In conclusion IIM patient serum, but not total IgG, impairs force production in skeletal muscle fibers. As the experiments were performed in isolated muscle, our results cannot be explained by infiltrating immune cells, impaired neuronal or vascular functions. This suggests that humoral factors play a direct role in the pathogenesis of muscle weakness in recent onset IIM.

physiology↗

bioRxiv2022

Autoantigenic properties of the aminoacyl tRNA synthetase family in idiopathic inflammatory myopathies

ObjectivesAutoantibodies are thought to play a key role in the pathogenesis of idiopathic inflammatory myopathies (IIM). However, up to 40% of IIM patients, even those with clinical manifestations of anti-synthetase syndrome (ASSD), test seronegative to all known myositis-specific autoantibodies (MSAs). We hypothesized the existence of new potential autoantigens among human cytoplasmic aminoacyl tRNA synthetases (aaRS) in patients with IIM. MethodsPlasma samples and clinical data from 217 patients with, 50 patients with ASSD, 165 without, and two with unknown ASSD status were included retrospectively, as well as serum from 156 age/sex-matched population controls. Samples were screened using a multiplex bead array assay for presence of autoantibodies against a panel of 118 recombinant protein variants, representing 33 myositis-related proteins, including all 19 cytoplasmic aaRS. ResultsWe identified reactivity towards 16 aaRS in 72 of the 217 patients. Twelve patients displayed reactivity against nine novel aaRS. The novel autoantibody specificities were detected in four patients previously seronegative for MSAs and in eight with previously detected MSAs. We also confirmed reactivity to four of the most common aaRS (Jo1, PL12, PL7, and EJ (n=45)) and identified patients positive for anti-Zo, -KS, and -HA (n=10) that were not previously tested. A low frequency of anti-aaRS autoantibodies was detected in controls. ConclusionOur results suggest that most, if not all, cytoplasmic aaRS may become autoantigenic. Autoantibodies against new aaRS may be found in plasma of patients previously classified as seronegative with potential high clinical relevance.

immunology↗

bioRxiv2020

Identifying novel B-cell targets for chronic inflammatory autoimmune disease by screening of chemical probes in a patient-derived cell assay

B-cell secretion of autoantibodies drives autoimmune diseases, including systemic lupus erythematosus and idiopathic inflammatory myositis. Few therapies are presently available for treatment of these patients, often resulting in unsatisfactory effects and helping only some of patients. We developed a screening assay for evaluation of novel targets suspending B-cell maturation into antibody secreting cells, which could contribute to future drug development. The assay was employed for testing 43 high quality chemical probes and compounds inhibiting under-explored protein targets, using primary cells from patients with autoimmune disease. Probes inhibiting bromodomain family proteins and histone methyl transferases demonstrated abrogation of B-cell functions to a degree comparable to a positive control, the JAK inhibitor tofacitinib. Inhibition of each target rendered a specific functional cell and potential disease modifying effect, indicating specific epigenetic protein targets as potential new intervention points for future drug discovery and development efforts.

immunology↗