The skewed frequency of B-cell subpopulation CD19+CD24 hiCD38 hi cells in peripheral blood mononuclear cells is correlated with the elevated serum sCD40L in patients with active systemic lupus erythematosus

CD19⁺CD24^hiCD38^hi cells play an essential role in maintaining immune homeostasis. CD40 signaling is involved in regulating the induction and function of CD19⁺CD24^hiCD38^hi cells. Changes in B-cell subpopulations and CD19⁺CD24^hiCD38^hi cells have been observed in systemic lupus erythematosus (SLE) patients. Whether changes in the B-cell subpopulation are related to the aberrant CD40 signaling in SLE patients remains unclear. In this study, we examined changes in the levels of CD19⁺CD24^hiCD38^hi cells and CD19⁺CD24^hiCD38^low cells in peripheral blood mononuclear cells and the serum level of soluble CD40 ligand (sCD40L) in 30 patients with SLE. Through routine biochemical assays and flow cytometry assay, we found that (1) the CD19⁺CD24^hiCD38^hi cell subset was upregulated in SLE patients compared to that in healthy controls (HCs) (P < 0.05); (2) the CD19⁺CD24^hiCD38^low cell subset was downregulated in SLE patients compared with that in HCs; and (3) CD38 expression was positively correlated with SLE manifestations and the serum sCD40L level (P < 0.05). In conclusion, the relative level of Bregs is significantly higher in SLE patients than in HCs and is positively correlated with disease activity and sCD40L level.