This study leverages spatial transcriptomics to uncover a specific transcriptional program triggered by autoantibodies after cellular internalization, offering a novel perspective on the mechanisms of autoimmune diseases. It suggests that targeting TGF-β1 or interfering with antibody delivery pathways could become future therapeutic strategies.
Literature Overview
The article, 'Spatial transcriptomics reveals mechanism of autoimmunity driven by internalised autoantibodies,' published in Annals of the rheumatic diseases, systematically investigates how anti-Mi-2 and anti-PM/Scl autoantibodies enter tissue cells via internalization, leading to target dysfunction and triggering specific inflammatory microenvironments. By integrating bulk RNA sequencing, in vitro IgG electroporation, immunofluorescence localization, and spatial transcriptomics, the study comprehensively dissects the direct molecular pathways of autoantibody-mediated pathogenesis. The findings not only validate the previously proposed hypothesis of 'direct pathogenicity of autoantibodies' but also, for the first time, reveal the spatial possibility of antibody RNA transfer from plasma cells to neighboring tissue cells, providing a unified framework for understanding the heterogeneity of multiple autoimmune diseases.Background Knowledge
Currently, the treatment of autoimmune diseases such as systemic sclerosis and dermatomyositis still largely relies on broad-spectrum immunosuppressants, lacking precise interventions targeting specific pathogenic mechanisms. Although autoantibodies such as anti-Mi-2 and anti-PM/Scl have been widely used for disease classification, whether they directly contribute to tissue damage has long been debated. The traditional view holds that antibodies targeting intracellular antigens cannot cross the plasma membrane and are thus considered disease markers rather than effector molecules. However, increasing evidence in recent years suggests that IgG can enter living cells through unknown mechanisms and affect key functional complexes such as nucleosome remodeling and the RNA exosome. The core challenges in this field are: How can we prove the functional role of internalized antibodies? What are their entry pathways? And do they affect non-muscle cells such as macrophages and fibroblasts? This study addresses these unresolved questions by selecting anti-Mi-2 and anti-PM/Scl as models and using spatially resolved transcriptomics to systematically dissect antibody-mediated cell-autonomous damage and the resulting local inflammatory programs, thereby transcending the traditional notion that 'humoral immunity only acts on extracellular targets.'
Research Methods and Experiments
The research team analyzed 814 muscle biopsy samples from a multicenter cohort covering various autoimmune diseases, with independent validation in external cohorts from France and Canada. Using bulk RNA sequencing, the authors confirmed highly specific transcriptional signatures in the muscles of patients with anti-Mi-2 and anti-PM/Scl: the former showed derepression of chromatin-silenced genes, while the latter exhibited accumulation of long non-coding RNAs. To validate the direct pathogenicity of IgG, the study employed electroporation to deliver purified IgG from patients into primary human skeletal muscle cells. The results demonstrated that this was sufficient to reproduce disease-specific transcriptional programs, with kinetic differences consistent with the biology of their targets—Mi-2-related effects appeared rapidly, whereas PM/Scl-dependent RNA accumulation was slower.
Immunofluorescence confirmed that IgG localized to the nuclei of muscle fibers and skin keratinocytes in anti-Mi-2 patients, but did not enrich in nucleoli; in contrast, in anti-PM/Scl patients, IgG specifically enriched in nucleoli, consistent with known antigen distributions. This phenomenon was further observed in other diseases such as anti-U1RNP, anti-Ku, and anti-Scl70, indicating that antibody localization closely matches the subcellular distribution of their target antigens, supporting the generality of internalization.
Spatial transcriptomic analysis represents the core innovation of this study. Using the 10x Genomics Xenium platform, the authors resolved the spatial distribution of transcriptional programs in situ. The results revealed that Mi-2-related derepression programs were primarily confined to specific muscle fibers, especially in the perifascicular regions, and were accompanied by downregulation of mature muscle genes (e.g., MYH1, TTN), suggesting functional impairment. Notably, these fibers exhibited reduced IFNAR1 expression, while surrounding fibroblasts and regenerating myoblasts strongly expressed type I interferon-induced genes, indicating a 'paracrine' interferon response.Key Conclusions and Perspectives
Research Significance and Prospects
This study fundamentally transforms our understanding of autoantibody function, proposing the 'internalization-driven pathogenesis' model as a common mechanism in multiple autoimmune diseases. From a drug development standpoint, targeting TGF-β1 or blocking antibody entry pathways (e.g., inhibiting efferocytosis or exosomal transfer) may represent novel therapeutic strategies. Additionally, the observation of local plasma cell release of antibody RNA suggests that eliminating tissue-resident plasma cells or disrupting their interactions with the microenvironment may yield greater therapeutic efficacy.
In clinical monitoring, spatial transcriptomic signatures could serve as precision classification tools to identify patient subgroups with active inflammatory programs, guiding personalized therapy. For example, patients with high TGF-β1 signaling may benefit from anti-fibrotic therapies, while those dominated by IFN-γ may be better suited for JAK inhibitors.
In disease modeling, this study offers new insights for building more realistic animal models: simulating the intracellular action of antibodies, rather than merely expressing or injecting them. For instance, conditional transgenic mice expressing pathogenic IgG or AAV-mediated delivery of antibody genes to specific tissues could be developed to recapitulate focal damage and inflammatory gradients.
Conclusion
This study, through multi-omics integration, establishes autoantibody internalization as a core mechanism of tissue damage in autoimmune diseases. Its innovation lies in redefining 'antibodies' from humoral factors to 'intracellular effector molecules,' and in elucidating the distinct roles of pathways such as TGF-β1 and type I interferon in focal injury. This discovery not only explains why specific antibody subtypes correspond to distinct clinical phenotypes, but also provides new targets for precise intervention. From bench to bedside, future therapies could target antibody delivery or intracellular signaling, combined with spatial molecular subtyping for personalized treatment. Particularly for refractory diseases such as dermatomyositis and systemic sclerosis, targeting TGF-β1 or the plasma cell microenvironment may break the vicious cycle of fibrosis and inflammation. This study provides a unifying pathogenic framework for the entire field of autoimmune diseases, marking a cognitive leap from 'markers' to 'drivers,' and is poised to reshape future diagnostic and therapeutic strategies.
