Serum Mac-2-binding protein (M2BP) is elevated in various chronic inflammatory diseases, and evidence suggests that glycosylation of M2BP induces discrete biological effects. However, the role of serum M2BP in systemic lupus erythematosus (SLE) is still unclear. Recently, a Wisteria floribunda agglutinin-positive–M2BP (WFA+–M2BP) immunoassay has shown promise in detecting highly glycosylated M2BP. In this study, by using WFA+–M2BP immunoassay, we measured serum M2BP in 203 SLE patients and evaluated its clinical significance. Eighty patients were classified as having active SLE and 123 patients as having inactive SLE. The median serum M2BP was higher in patients with active SLE than in those with inactive SLE (2.1 vs. 0.9, p < 0.001). In multivariate linear regression analysis, serum M2BP, anti-dsDNA, C3 and erythrocyte sedimentation rate (ESR) were associated with SLEDAI-2K. Serum M2BP also strongly correlated with laboratory variables related to SLEDAI-2K, ESR and C-reactive protein. Furthermore, multivariate logistic regression analysis demonstrated that serum M2BP was useful in predicting active SLE. Finally, following immunosuppressive treatment, elevated serum M2BP significantly decreased along with improvement in disease activity. These findings suggest that serum M2BP might contribute to the inflammatory process in SLE, and measuring serum M2BP might be a useful marker to assess SLE disease activity.
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