Espinosa, Gerard

ABSTRACT Autoantibody internalization has been implicated in autoimmune disease pathogenesis, yet its mechanisms, and generality across different diseases, cell types, and affected tissues remain poorly defined. Using bulk RNA sequencing, we identified reproducible, autoantibody-specific transcriptomic signatures consistent with autoantigen dysfunction in muscle biopsies from patients with anti-Mi2 dermatomyositis and anti-PM/Scl scleromyositis across independent cohorts. Electroporation of purified patient IgG into primary cultures of healthy cells was sufficient to induce the corresponding transcriptomic programs in vitro . Direct immunofluorescence demonstrated immunoglobulin internalization into subcellular compartments matching the localization of the autoantigen in different affected tissues. Spatial transcriptomic analyses revealed that antibody-secreting cells translocated cytoplasmic material (i.e., immunoglobulin RNA) into adjacent affected cells expressing autoantibody-specific transcripts. The disease-specific transcripts were present not only in muscle fibers, but also in other cells, including macrophages, endothelial cells, and fibroblasts. Autoantibody-induced transcriptomic programs were associated with cell damage and autoantibody-specific reactive inflammatory programs, including activation of type I interferon and TGF-ß1 signaling in anti-Mi2 dermatomyositis and activation of type II interferon in anti-PM/Scl scleromyositis. Antibody internalization was also observed in different tissues from patients with other autoimmune diseases, including anti-U1RNP mixed connective tissue disease, anti-Ku overlap syndrome, and anti-Scl70 systemic sclerosis. Together, these findings establish autoantibody internalization as a shared pathogenic mechanism across diverse autoimmune diseases, providing a unifying framework for conditions driven by autoantibodies against intracellular antigens.

Abstract Objective To examine the influence of demographics on organ damage in a broad, multiethnic cohort of patients with Behçet’s syndrome (BS). Methods In this cross-sectional ancillary analysis of the PROBE project, the investigated demographic variables were sex, age, education level and geographic area of residence. Damage was measured by the BS Overall Damage Index (BODI). Multivariate linear (β) and logistic (adjusted odds ratio [adjOR]) regression analyses examined associations between demographics and the extent and prevalence of damage. Results A total of 970 patients were enrolled. The median (interquartile range) age was 40 (31–50) years; 56.5% were males; 21.4% had a low level of education. The median BODI score was 1 (0–3), with 65.6% of patients having a BODI ≥1. Males had higher damage (β 0.103) and a higher prevalence of total (adjOR 1.7, per 10 years), ocular (adjOR 1.6), and vascular (adjOR 2.1) damage. Age was associated with greater damage (β 0.104), and a higher prevalence of overall (adjOR 1.4), neuropsychiatric (adjOR 1.2) and miscellaneous (adjOR 2.0) damage. Low education was associated with a greater frequency of overall (adjOR 1.9) and ocular (adjOR 1.6) damage. North African patients experienced greater damage than South European (β 0.400) and Middle Eastern (β 0.314) patients, as well as a higher risk of overall damage (adjOR 13.9 and 10.7, respectively) across all organ domains, except for the reproductive and gastrointestinal systems. Conclusions This study demonstrates how the extent, prevalence and characteristics of damage in BS vary with demographic factors, underscoring their importance in research and personalized management.