Hyporesponsiveness to toll-like receptor 9 (TLR9) stimulation of B cells from systemic lupus erythematosus (SLE) patients in relation to their disease activity. (A) Heat map of cytokines from group 1 and 2 secreted by B cells upon TLR9 stimulation (dark blue for the lowest, to red for the highest concentration of cytokine in the supernatant). SLE patients were ordered according to their disease activity from low systemic lupus erythematosus disease activity index (SLEDAI) in green, to high SLEDAI in red. (B) Direct correlation between individual cytokines from group 1 and 2 and lupus activity (SLEDAI score). Significant inverse correlation was found between the SLEDAI score and individual cytokines produced by B cells upon TLR9 stimulation (IL-6, IL-9, IL-17A, IFN-γ, IP-10, MIP-1α, MIP-1β, and TNF-α). Healthy donors (HD) are plotted as reference. (Spearman r correlation test; *P <0.05 and **P <0.01). IP-10: IFNγ-induced protein 10; MIP, macrophage inflammatory proteins; VEGF, vascular endothelial growth factor.