Characteristics of purified anti-beta(2)GPI IgG N-glycosylation associate with thrombotic, obstetric and catastrophic antiphospholipid syndrome

Objective Anti-beta-2 glycoprotein I (anti-beta 2GPI) antibodies, defined as primary pathogenic antibody in antiphospholipid syndrome (APS). It has been reported that IgG Fc N-glycosylation affects IgG effector, we aim to investigate the association of Fc glycosylation profiles of purified anti-beta 2GP1 IgG with clinical features of APS. Methods We purify anti-beta(2)GPI IgG and total IgG from 82 APS patients including nine catastrophic antiphospholipid syndrome (CAPS) patients, as well as total IgG from 103 healthy controls to quantitatively analyse all detectable Fc N-glycanforms of all IgG subclasses with Multiple Reaction Monitoring (MRM) method based on UPLC-ESI-QqQ mass spectrometry. Results Both purified anti-beta(2)GPI IgG and APS total IgG showed altered N-glycan profiles when compared with healthy control (HC) IgG. Anti-beta(2)GPI IgG presented with lower galactosylation, increased bisection and core fucosylation compared with APS total IgG and HC IgG. We found higher galactosylation of a beta 2GPI IgG2 in thrombotic APS compared with the obstetric APS, and lower galactosylation of a beta 2GPI IgG2 associated with late pregnancy morbidity. Moreover, low galactosylation of all anti-beta(2)GPI IgG subclasses, increased bisection and core fucosylation of anti-beta(2)GPI IgG1/2 were strongly associated with CAPS and triple positivity of antiphospholipid antibodies (aPLs). Conclusion We comprehensively characterize the N-Glycans landscape of both anti-beta 2GP1 and total IgG in APS. Altered N-glycan profiles of anti-beta 2GPI IgG enables enabled the antibodies with proinflammatory properties. Furthermore, we associated levels of IgG Fc-glycosylation with clinical features antiphospholipid syndrome. These findings could increase our understanding of anti-beta(2)GPI antibody mediated mechanisms in APS and be used to develop diagnostics and new target treatments.