Elevated CD19⁺Siglec-10⁺ B cell levels are correlated with systemic lupus erythematosus disease activity

Systemic lupus erythematosus (SLE) is a chronic autoimmune disease characterized by B cell dysregulation and the breakdown of self-tolerance, leading to pathogenic autoantibody production. Human Siglec-10 is a member of the sialic acid-binding immunoglobulin-type lectin (Siglec) family and a B cell surface coreceptor that inhibits B cell receptor-induced signalling. However, to date, no report has investigated CD19⁺Siglec-10⁺ B cells in SLE patients. Thus, this study aimed to measure the population of CD19⁺Siglec-10⁺ B cells in patients with SLE and its correlation with disease activity.

Flow cytometry was employed to measure the population of CD19⁺Siglec-10⁺ B cells in peripheral blood mononuclear cells (PBMCs) of both SLE patients and healthy controls (HCs). The correlation of the proportion of CD19⁺Siglec-10⁺ B cells with the values of SLE disease activity was analysed. PBMCs from HCs were challenged with serum from active SLE, inactive SLE, or HCs, and the proportion of CD19⁺Siglec-10⁺ B cells was then assessed. The effect of dexamethasone (DEX) or hydroxychloroquine (HCQ) treatment on the proportion of CD19⁺Siglec-10⁺ B cells in PBMCs from SLE patients was also determined.

The proportion of CD19⁺Siglec-10⁺ B cells in SLE patients was significantly elevated (P < 0.05), correlated positively with the SLEDAI score (r = 0.304; P = 0.018) and negatively with complement component 3 (C3) (r = -0.283; P = 0.04). In vitro assays indicated that sera from active SLE patients could significantly enhance the proportion of CD19⁺Siglec-10⁺ B cells (P < 0.05), while HCQ treatment significantly attenuated their proportions (P < 0.01).

The elevation of CD19⁺Siglec-10⁺ B cells and their correlation with disease activity may suggest a role for Siglec-10 in the pathogenesis and progression of SLE and provide a serum biomarker for SLE activity.