Introduction B-cells have a well-established role in the pathogenesis of rheumatoid arthritis (RA), illustrated by the successful treatment of RA with B-cell depletion therapy.¹Sialic acid (SA) is a 9-carbon backbone sugar involved in many immune system functions including cell migration, adhesion and activation.² In RA, sialylation of the B-cell surface, including membrane bound IgM, has been found to differ from healthy control B-cells. These changes have been attributed to alterations in antibody glycosylation which lead to the highly inflammatory phenotype of disease-specific autoantibodies.³ Recently it has been shown that surface glycosylation of regulatory T-cells is altered by activating stimuli – suggesting functional consequences for cell surface glycans.⁴ Functional effects of surface glycans in B-cells in RA have not been well established.

Objectives The aim of this study is to investigate surface sialylation of B-cells from patients with RA at different stages of disease, and to examine functional consequences of B-cell surface sialylation.

Methods Sialylation of peripheral blood mononuclear cells isolated from 7 patients with either ‘pre-RA’ or RA (3 patients with ACPA+ ‘pre-RA’, 1 patient with a diagnosis of new onset, ≤12 months symptom duration, and 3 patients with established disease) was analysed by flow cytometry using biotinylated Sambucus Nigra (SNA) Lectin, to bind to α2,6 SA, with PE-conjugated streptavidin. MESF beads were used to standardise the measurement of fluorescence intensity. B-cells were activated in culture with anti-CD40 and anti-IgM.

Results Initial data suggests that B-cell surface sialylation may be higher in patients with pre-RA (MESF: 13765±170) or new onset RA (13094) than in patients with established RA (12431.3±339). Sialylation also tended to be higher on plasmablasts (1396±991) than on memory (13067±496) or naïve B-cells (13127±710). Upon in vitro activation with anti-CD40 and anti-IgM, sialylation tended to decrease in plasmablasts (20042±679 vs 16200.5±1261).

Conclusions Preliminary results suggest that B-cell surface sialylation may vary according to stage of disease and B-cell subset. Sialylation may also be related to B-cell activation. Further investigations will be carried out to better understand variations in surface sialic acid and examine the relationship between B-cell function and surface sialylation.

References

1. . Mok CC. Drug Des Devel Ther2014;8:87–100.

2. . Varki A, Gagneux P. Ann N Y Acad Sci2012;1253(1):16–36.

3. . Pfeifle R, et al. Nature Immunology2017;18:1.

4. . Cabral J, et al. Frontiers in Immunology2017;8:987.

Disclosure of interest None declared