Elevated soluble CD226 in Takayasu arteritis is useful for differentiation from giant cell arteritis and is associated with the disease activity and prognosis

Abstract Background Takayasu arteritis (TAK) is characterized by vascular injury, in which endothelial cells and immune cells, such as natural killer (NK) cells, have key roles. CD226 is an activating receptor expressed on the cell membrane of NK cells and T cells, and the soluble form of CD226 (sCD226) is increased in diseases involving these cells. Therefore, we investigated the utility of serum sCD226 as a biomarker for TAK. Methods Serum sCD226 levels were measured using an enzyme-linked immunosorbent assay in 34 patients with TAK and 21 patients with giant cell arteritis (GCA). The associations between sCD226 levels and the angiographic classification, disease activity, and prognosis of TAK were analysed. Results Serum sCD226 levels were significantly higher in TAK patients than in GCA patients. In patients with TAK, serum sCD226 levels were significantly elevated in the group of type Ⅴ, which had the most extensive lesions, compared with the group of other types excluding type Ⅴ. Serum sCD226 levels were also elevated in patients with active TAK and in those with poor responses to corticosteroids. Regarding prognosis, the cumulative probability of relapse was higher in patients with high sCD226 levels than in those with low sCD226 levels. Conclusions Serum sCD226 levels differentiated TAK from GCA and were associated with disease activity and relapse of TAK. Serum sCD226 may be a useful biomarker for the management of TAK.