Expression of SR-A on blood DCs and inhibition of anti–SR-A Ab binding by fucoidan. (A) iMDDCs were prepared by culturing monocytes (10⁶) with GM-CSF and IL-4 for 6 days. (Left panel) The cells were harvested and the cell lysates (30 μg/mL) were subjected to immunoblot analyses using an anti–human SR-A Ab. The cell lysates from PMA-stimulated THP-1 cells were used as a positive control. (Right panel) Monocytes and iMDDCs were pretreated with isotype-matched Ab for 1 hour and then incubated with Alexa Fluor 488–conjugated anti–SR-A Ab (5 μg/mL) in the presence or absence of fucoidan (50 μg/mL) for 30 minutes at 4°C, after which they were analyzed by fluorescence-activated cell sorter. (B) PBDCs were isolated using BDCA-1, -2, and -4–conjugated magnetic beads from peripheral blood mononuclear cells. The cells were incubated with Alexa-conjugated anti–SR-A Ab and PE-conjugated CD11c in the presence or absence of fucoidan for 30 minutes, and Ab binding was then analyzed. (C) CD11c^highCD123^low (mDC) and CD11c^lowCD123^high (pDC) cells were gated and examined for anti–SR-A Ab binding. One representative experiment of 3 is shown.