Immunoglobulin G glycosylation and clinical outcome in rheumatoid arthritis during pregnancy.

OBJECTIVE: To determine whether clinical outcome during pregnancy in rheumatoid arthritis (RA) is associated with changes in the levels of exposed immunoglobulin G (IgG) terminal sugars.

METHODS: Serum IgG glycosylation from 23 pregnant patients with RA was analyzed during the prenatal, antenatal, and post-partum periods. Patients were randomly selected on the basis of whether they achieved spontaneous remission (n = 11) or did not remit (n = 12); of the latter group 6 patients experienced a relapse in disease activity. Levels of exposed terminal IgG sugars, galactose (Gal), N-acetylglucosamine (GlcNAc), and sialic acid (SA), were estimated in a lectin binding assay using Ricinis (communis, Bandeiraea simplicifolia II, and Sambucus nigra, respectively.

RESULTS: Exposed Gal levels increased (p<0.02) and GlcNAc levels decreased (p<0.05) in the antenatal period, and returned to preconception levels during post-partum. GlcNAc rebound was instantaneous (p<0.005), whereas Gal remained high for a further 10 weeks. SA did not undergo any major changes. Remission was associated with an earlier and significantly greater antenatal reduction in GlcNAc (2nd and 3rd trimester; p<0.02) in comparison to the groups that did not experience a decrease in disease activity. Analysis of individual IgG samples during the first trimester revealed a significant negative correlation between Gal and GlcNAc in the remission group (r = -0.80; p<0.05), which was opposite to that found in the relapse group (r = +0.87; p<0.03). There was no significant difference between the groups with regard to the timing and/or incidence of a post-partum flare of disease.

CONCLUSION: Temporal changes in the levels of IgG terminal sugars, in particular exposed GlcNAc, are integrally associated with the clinical manifestation of RA in pregnancy. Generation of IgG sugar micro-heterogeneity is complex and understanding it may help unravel pathogenic features associated with RA.