Immunoglobulin G/immunoglobulin M autoantibody ratios in incomplete systemic lupus erythematosus

Abstract

Objective

Immunoglobulin G (IgG) autoantibodies in systemic lupus erythematosus (SLE) are considered pathogenic, whereas immunoglobulin M (IgM) autoantibodies may have protective effects. The aim of this study was to identify whether IgG/IgM autoantibody ratios differ between patients with incomplete systemic lupus erythematosus (iSLE), patients with SLE, and healthy controls (HCs), and whether IgG/IgM autoantibody ratios relate to progression from iSLE to SLE.

Method

This prospective cohort study included 34 iSLE patients, 41 SLE patients, and 11 HCs. IgG and IgM anti-dsDNA, anti-Ro52, and anti-Ro60 were measured by fluoro-enzyme immunoassay in serum samples obtained at baseline in all groups and in follow-up samples of up to 5 years for iSLE patients. Correlations between IgG/IgM autoantibody ratios, interferon signature, and clinical parameters were also assessed.

Results

At baseline, IgG anti-dsDNA, anti-Ro52, anti-Ro60, and IgM anti-dsDNA were elevated in iSLE and SLE patients. IgG/IgM anti-dsDNA and anti-Ro52 ratios were similar between groups, while IgG/IgM anti-Ro60 ratios were significantly elevated in iSLE and SLE patients compared to HCs. IgG/IgM autoantibody ratios were not correlated with interferon signature or clinical parameters. IgG/IgM ratios at baseline were similar and remained relatively stable during a median follow-up of 18 months in non-progressors and six iSLE patients who progressed to SLE.

Conclusion

IgG anti-dsDNA, anti-Ro52, anti-Ro60, and IgM anti-dsDNA were elevated in iSLE and SLE patients, which was not apparent from the respective IgG/IgM ratios only. IgG/IgM autoantibody ratios remained relatively stable over up to 5 years in iSLE non-progressors and six patients who progressed to SLE.

Acknowledgement

We would like to thank Dr Wietske Lambers for her valuable contribution regarding collection of clinical data.

Disclosure statement

Svenja Henning: speaker for Thermo Fisher Scientific, for which fees were paid to the institution. No potential conflict of interest was reported by the remaining authors.

Authors’ contributions

Svenja Henning: methodology, formal analysis, investigation, data curation, writing – original draft, visualization, and project administration; Johanna Westra: conceptualization, methodology, writing – review and editing, supervision, and project administration; Caroline Roozendaal: conceptualization, methodology, and writing – review and editing; Greet Haarsma-de Boer: formal analysis, investigation, data curation, and writing – review and editing; Juan J Fierro: writing – review and editing, and visualization; Hendrika Bootsma and Barbara Horvath: writing – review and editing; Karina de Leeuw: conceptualization, methodology, investigation, writing – review and editing, supervision, project administration, and funding acquisition.

Supplementary material

Supplemental data for this article can be accessed online at https://doi.org/10.1080/03009742.2024.2321700.

Additional information

Funding

This work was supported by ReumaNederland [15-1-401 to KdL]; Thermo Fisher Scientific kindly provided test materials for analysing autoantibodies with FEIA-EliA.