Increased Proportion of CD226(+) B Cells Is Associated With the Disease Activity and Prognosis of Systemic Lupus Erythematosus

BACKGROUND: CD226, an activating receptor expressed on the surface of natural killer (NK) cells and T cells, is also seen on B cells and CD226 polymorphism is associated with systemic lupus erythematosus (SLE). Because the specific roles of CD226(+) B cells in SLE are still unknown, we investigated the association of CD226(+) B cells with SLE. METHODS: We measured CD226 expression on B cells and its subsets using flow cytometry in 48 SLE patients and 24 healthy controls (HCs). We assessed the relationships between CD226(+) B cells and SLE Disease Activity Index 2000 (SLEDAI-2K), clinical manifestations, laboratory data, and prognosis after 12 months. RESULTS: The proportions of CD226(+) cells in whole B cells and all its subsets were significantly higher in SLE patients than HCs. In SLE patients, the proportions of CD226(+) B cells and CD226(+) switched-memory (SM) B cells were significantly correlated with SLEDAI-2K scores and anti-dsDNA antibody titers, and negatively correlated with serum complement levels. Moreover, basal percentages of CD226(+) B cells and CD226(+) SM B cells were low in patients who were in Lupus Low Disease Activity State after 12 months. In patients with renal involvement, the proportion of CD226(+) B cells increased. Additionally, the proportion of CD226(+) B cells was higher in patients who were not in complete renal remission after 12 months. CONCLUSIONS: Increased proportion of CD226(+) B cells was associated with disease activity and prognosis of SLE. CD226(+) B cells may be a useful biomarker for the management of SLE.