In pregnant patients with anti-citrullinated protein antibody (ACPA)-positive rheumatoid arthritis (RA), the change in galactosylation of ACPA-IgG is associated with changes in disease activity, according to results published online in the Annals of the Rheumatic Diseases.
These results may indicate that the galactosylation of ACPA-IgG is more pathogenically relevant than that of total immunoglobulin G (IgG) in patients with ACPA-positive RA. The results may also explain why patients with ACPA-positive RA improve less during pregnancy compared with patients with ACPA-negative RA.
The study included 112 participants from the Pregnancy-induced Amelioration of Rheumatoid Arthritis cohort, a prospective study designed to investigate pregnancy-associated improvement of RA. The researchers purified ACPA-IgGs from participant sera. They used mass spectrometry to characterize the fragment crystallizable (Fc)glycosylation profile of ACPA-IgGs. The profile was then compared with that of total IgG derived from the participants or from ACPA-negative patients.
The results indicated that all ACPA-IgG subclasses showed significant changes in the levels of galactosylation and sialylation during pregnancy, although this effect is less pronounced than in total IgG.
While the pregnancy-induced increase in ACPA-IgG galactosylation was associated with lower disease activity, the ACPA-IgG sialylation was not.
In patients who were ACPA-positive, there was no association between changes in the galactosylation of total IgG and disease activity, although this association was present in patients who were ACPA-negative.
Bondt A, Hafkenscheid L, Falck D, et al. ACPA IgG galactosylation associates with disease activity in pregnant patients with rheumatoid arthritis [published online April 3, 2018]. Ann Rheum Dis. doi:10.1136/ annrheumdis-2018-212946