Association of Elevated Serum Soluble Cd226 Levels With the Disease Activity and Flares of Systemic Lupus Erythematosus

Abstract

Background: CD226 is an activating receptor expressed on the cell surface of natural killer cells and T cells. A soluble form of CD226 (sCD226) is known to be shed from the membrane type of CD226 (mCD226). Although CD226 polymorphism and mCD226 are known to be involved in systemic lupus erythematosus (SLE), the involvement of sCD226 in SLE is still unknown. Therefore, we aimed to reveal the association of sCD226 with SLE.Methods: We measured serum sCD226 levels using an enzyme-linked immunosorbent assay in 58 SLE patients and 33 healthy controls (HCs) and evaluated their associations with SLE Disease Activity Index 2000 (SLEDAI-2K), clinical manifestations, and laboratory data. We defined the maximum values of sCD226 in HCs as a cut-off level and compared the cumulative probability of flare for patients with high and low sCD226 levels. Results: Serum sCD226 levels showed no significant differences between SLE patients and HCs. However, sCD226 levels were significantly elevated in active SLE patients with a SLEDAI-2K score of ≥20 compared with HCs. In SLE patients, sCD226 levels were significantly correlated with SLEDAI-2K scores and anti-dsDNA antibody titers. Moreover, the cumulative probability of flare was markedly higher in patients with high sCD226 than in those with low sCD226. In patients with neuropsychiatric involvement, sCD226 levels were elevated and reflected neuropsychiatric disease activity. Conclusion: Serum sCD226 levels were associated with disease activity and flares of SLE. Thus, it may be a useful biomarker for SLE, and its monitoring allows for more precise SLE management.