SR-A–mediated maturation of fucoidan-stimulated blood DCs. (A) iMDDCs (10⁶) were left untreated (Untreated) or transfected with DharmaFECT alone (Shock), 200 nM siRNA of SR-A (SR-A siRNA), or 200 nM nontargeting siRNA (Non-siRNA) for 24 hours. Next, the cells were harvested and incubated with Alexa Fluor 488–conjugated anti–SR-A Ab for 30 minutes at 4°C and then analyzed by fluorescence-activated cell sorter. (Bottom panel) The expression of SR-A proteins in siRNA-transfected iMDDCs was then measured by Western blot. (B) iMDDCs were treated and harvested as in panel A. Control (Non-siRNA) and SR-A–deficient iMDDCs were then stimulated with the indicated concentrations of fucoidan or LPS for 24 hours, after which the expression level of CD83 was measured by flow cytometry. *P < .01 compared with Non-siRNA. (C) PBDCs were pretreated with control IgG or anti–SR-A Ab (5 μg) for 1 hour and further cultured in the presence or absence of fucoidan. After 24 hours, CD11c^highCD123^low and CD11c^lowCD123^high cells were gated and examined for CD83 expression. (Top panel) The expression levels of CD123, CD11c, and CD83 on freshly isolated PBDCs. (D) CD11c⁺ mDCs were purified using a cell sorter as in Figure 2B and then treated with control IgG or anti–SR-A Ab for 24 hours. The results shown represent the mean ± SD of 3 independent experiments.