The C1q–DC-SIGN interaction is Ca2+ dependent and reduced by mannan. (A) ELISA experiments were performed using purified, soluble C1q or various synthetic C1q-A peptides (aa 155-164 for RR, aa 155-164 for RR at 162/163 changed to QQ). Then, 2.5 μg/mL of biotinylated DC-SIGN was added to the C1q- or synthetic peptide–coated plates in the presence or absence of 10mM EDTA and binding was detected using streptavidin-AP. One representative experiment is shown (n = 3). (B) Mannan reduced the binding of C1q to DC-SIGN significantly. ELISA experiments were performed using 2.5 μg/mL of biotinylated DC-SIGN premixed with 2 mg/mL of mannan for 15 minutes at RT. DC-SIGN/mannan was added to C1q- or BSA-coated plates and binding was detected using streptavidin-AP. One representative experiment is shown (n = 3). **P < .01.
