Fig. 2

A The expression levels of S100A8 and S100A8/A9 on the cell surface and intracellular peripheral blood CD19 + cells of HC, stable SLE, and active SLE were evaluated using flow cytometry. S100A8 and S100A8/A9 on the cell surface of B cells in active SLE were significantly increased compared to those in HC. B In the intracellular staining, no significant difference was observed among the groups. C, D The cell surface (C) and intracellular (D) expression of S100A8 and S100A8/A9 were evaluated in various connective tissue diseases (CTDs); however, its expression was not as high as that in SLE. Active SLE was classified as having SLEDAI score ≥ 6. Statistical significance is denoted by asterisks: **, p < 0.01; ***, p < 0.001 in Kruskal–Wallis. Other CTDs include polyarteritis nodosa (N = 4), Takayasu’s arteritis (N = 8), eosinophilic granulomatosis with polyangiitis (N = 6), granulomatosis with poly angiitis (N = 2), microscopic polyangiitis (N = 5), polymyositis/dermatomyositis (N = 9), Behçet disease (N = 2), IgG4-related disease (N = 1), Sjögren syndrome (N = 5), relapsing polychondritis (N = 5), systemic sclerosis (N = 6), ankylosing spondylitis (N = 1), adult-onset Still’s disease (N = 1), and rheumatoid arthritis (N = 5)