Human Immunoglobulin A1 hinge region (IgA1-HR)

The Human Immunoglobulin A1 (IgA1) hinge region is a specialized proline-rich segment of the IgA1 heavy chain that provides structural flexibility between the antigen-binding Fab domains and the effector Fc domain [8, 13]. This region is unique to the IgA1 subclass and contains multiple O-linked glycosylation sites that are typically galactosylated in healthy individuals [11, 19]. In the pathogenesis of IgA nephropathy (IgAN), the hinge region undergoes aberrant glycosylation, resulting in the production of galactose-deficient IgA1 (Gd-IgA1) [5, 34]. These truncated glycans expose neoepitopes that are recognized by IgG autoantibodies, leading to the formation of pathogenic immune complexes that deposit in the renal mesangium and trigger glomerular injury [7, 12]. Pathogenic bacteria such as Neisseria meningitidis and Haemophilus influenzae produce IgA1 proteases that specifically target and cleave this hinge region to evade mucosal immunity [15, 31]. Therapeutic interventions targeting the IgA1 hinge region include recombinant IgA1 proteases, which cleave the hinge to dissolve existing deposits, and molecular degraders like BHV-1400 that selectively target Gd-IgA1 for clearance [25, 26, 38]. Monitoring Gd-IgA1 levels and anti-hinge autoantibodies serves as a critical biomarker for disease activity and treatment efficacy in patients with IgAN [9, 33].

Other names

IgA1 hinge regionO-glycosylated hinge region of IgA1Galactose-deficient IgA1 hinge regionGd-IgA1 hinge

Proteolysis of the IgA1 hinge region to dissolve immune complexes and targeted degradation of galactose-deficient IgA1 via ASGPR-mediated endocytosis.