The interactions of
antibodies with myeloid Fcγ receptors and the
complement system are regulated by an Asn297-linked
glycan in the Fc portion of
IgG. Alterations of serum
IgG-Fc glycosylation have been reported in various
autoimmune diseases, and correlate with treatment response and disease activity. We hypothesized that
IgG-Fc glycosylation is altered in
immune thrombocytopenia (
ITP) and associates with response to anti-CD20
monoclonal antibody treatment (
rituximab).
IgG-Fc glycosylation was analyzed by liquid chromatography-mass spectrometry. We found that
IgG-Fc glycosylation was identical between refractory
ITP patients (HOVON64 trial; N = 108) and healthy controls (N = 120). Two months after
rituximab treatment, we observed a shift in Fc glycosylation, with a mean 1.7% reduction in galactosylation for
IgG1 and
IgG4 and a mean 1.5% increase for bisection in
IgG1,
IgG2/3 and
IgG4 (adjusted p < 1.7 × 10-3 and p < 2 × 10-4, respectively). Neither baseline nor longitudinal changes in
IgG-Fc glycosylation after
rituximab were associated with clinical treatment response. We conclude that
IgG-Fc glycosylation in refractory
ITP is similar to healthy controls and does not predict treatment responses to
rituximab. The observed changes two months
after treatment suggest that
rituximab may influence total serum
IgG-Fc glycosylation. Overall, our study suggests that the pathophysiology of refractory
ITP may differ from other
autoimmune diseases.