Immunoglobulin G4 autoantibody (IgG4 autoantibody)

Immunoglobulin G4 (IgG4) autoantibodies are a specific subclass of self-reactive antibodies that play a central role in the pathogenesis of various autoimmune conditions, most notably IgG4-related disease (IgG4-RD) and specific organ-specific disorders like MuSK-positive myasthenia gravis and pemphigus vulgaris (Koneczny, I., 2018, Frontiers in Immunology). Structurally, IgG4 is unique among immunoglobulins due to its ability to undergo Fab-arm exchange, a process where heavy-light chain pairs are swapped, often resulting in functionally monovalent antibodies that cannot cross-link antigens or form large immune complexes (van der Neut Kolfschoten, M., et al., 2007, Science). While IgG4 is generally considered non-inflammatory because it poorly activates the complement system and has low affinity for most Fc gamma receptors, its pathogenicity arises from its ability to physically block essential protein-protein interactions or disrupt cellular signaling (Huijbers, M. G., et al., 2015, Nature Reviews Rheumatology). In clinical practice, these antibodies serve as critical biomarkers for diagnosis and disease activity monitoring (Stone, J. H., et al., 2012, NEJM). Therapeutic intervention typically involves B-cell depletion therapies like rituximab to stop production or the use of FcRn antagonists like efgartigimod to reduce the half-life and circulating levels of these pathogenic immunoglobulins (Ulrichts, P., et al., 2018, Journal of Clinical Investigation).

Other names

IgG4-type autoantibodyIgG4-class autoantibodyAutoimmune IgG4Pathogenic IgG4

Therapeutic strategies focus on depleting the B-cell and plasma cell populations responsible for producing these antibodies (e.g., via CD20 or CD19 inhibition) or accelerating their clearance from circulation by inhibiting the neonatal Fc receptor (FcRn) to prevent recycling.