C1q binds to DC-SIGN. (A) C1q was added to DC-SIGN–coated plates and binding was detected using pAb anti-C1q Ab in an antigen-capture ELISA. One representative experiment is shown (n = 3). (B) Normal human serum (NHS; 150 μL) that was C3, factor H (FH), and C1q depleted was incubated overnight at 4°C with 2 μg of biotinylated DC-SIGN and added to neutravidin-coated resin beads for 2 hours at RT. Bead-bound proteins were visualized by Western blotting using pAb C1q, followed by HRP- conjugated secondary Ab. Soluble C1q protein was used instead of human serum as a positive control, shown as “(+) cont.” (n = 2).