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A subset of autoimmune diseases is characterized by predominant pathogenic IgG4 autoantibodies (IgG4-AID). Why IgG4 predominates in these disorders is unknown. We hypothesized that dysregulated B cell maturation or aberrant class switching causes overrepresentation of IgG4 B cells and plasma cells. Therefore, we compared the B cell compartment of patients from four different IgG4-AID with two IgG1-3-AID and healthy donors, using flow cytometry. Relative subset abundance at all maturation stages was normal, except for a, possibly treatment-related, reduction in immature and naïve CD5 cells. IgG4 B cell and plasma cell numbers were normal in IgG4-AID patients, however they had a (sub)class-independent 8-fold increase in circulating CD20CD138 cells. No autoreactivity was found in this subset. These results argue against aberrant B cell development and rather suggest the autoantibody subclass predominance to be antigen-driven. The similarities between IgG4-AID suggest that, despite displaying variable clinical phenotypes, they share a similar underlying immune profile.
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http://dx.doi.org/10.1016/j.clim.2023.109817 | DOI Listing |
Objective: Autoimmune nodopathies (AINs) are a group of rare, acquired autoimmune neuropathies with distinct clinical features and the presence of circulating autoantibodies - often of the immunoglobulin G4 (IgG4) subclass - targeting proteins at the node of Ranvier. Defects in B cell tolerance checkpoints have been implicated in several autoimmune diseases. Prior work identified defective B cell tolerance-reflected by a high frequency of self-reactive naïve B cells-in patients with MuSK-positive myasthenia gravis (MG), mediated by IgG4 autoantibodies.
View Article and Find Full Text PDFOrphanet J Rare Dis
August 2025
Department of Rheumatology, The First Affiliated Hospital of Nanjing Medical University, 300 Guangzhou Road, Nanjing, 210029, Jiangsu, China.
Background: Rapidly progressive interstitial lung disease (RP-ILD) is a severe, often fatal complication in patients with anti-melanoma differentiation-associated gene 5 antibody-positive dermatomyositis (MDA5 DM). Early prediction of RP-ILD still remains challenging. We aimed to explore the link between anti-MDA5 IgG subtypes and ILD prognosis in individuals with MDA5 DM.
View Article and Find Full Text PDFNephrol Dial Transplant
August 2025
Renal Division, Peking University First Hospital, Beijing, China.
Background And Hypothesis: Anti-glomerular basement membrane (anti-GBM) disease is an autoimmune kidney disease in which autoantibodies are directed against GBM components. Type IV collagen and laminin α5β2γ1 (LM521) within GBM are two major target antigens in anti-GBM disease. Perlecan is a type of heparan sulfate proteoglycan, ubiquitously expressed in basement membranes.
View Article and Find Full Text PDFFront Immunol
July 2025
Faculty of medicine, Universiti Kebangsaan Malaysia, Cheras, Malaysia.
Background: Rheumatoid arthritis (RA) is an autoimmune disorder characterized by chronic joint inflammation driven by a complex interplay of autoantibodies, cytokines, and chemokines. While the role of proinflammatory cytokines, such as interleukin-1(IL-1), interleukin-6(IL-6), and tumor necrosis factor-α (TNF-α), in the pathogenesis of RA has been well-established, the contribution of the immunoglobulin G subclass IgG4 remains a topic of ongoing investigation. This cross sectional study aim was to compare the levels of IgG4 and these key inflammatory cytokines in Malaysian patients with RA.
View Article and Find Full Text PDFNeurol Neuroimmunol Neuroinflamm
September 2025
Department of Neurology, Yale School of Medicine, New Haven, CT.
Background And Objectives: Acetylcholine receptor (AChR) autoantibodies contribute to myasthenia gravis (MG) pathogenesis through 3 mechanisms: complement activation, receptor internalization, and acetylcholine (ACh) binding site blocking. Recently approved therapies target these autoantibodies by inhibiting the complement pathway or blocking the neonatal Fc receptor, reducing IgG autoantibody levels. However, these approaches have limitations: complement inhibitors do not address complement-independent mechanisms, and FcRn blockers only target IgG.
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