C1q-mediated activation of NF-κB requires DC-SIGN. Phosphorylation of Iκκα/β in the DC-SIGN–expressing human THP-1 cell line was determined after treatment with Abs to DC-SIGN (AZND1 and MR-1; 20 μg/mL at 37°C for 20 minutes) and/or C1q (at 37°C for 10 minutes). After cell lysis, phosphorylated Iκκα/β and p38 were detected using specific mAbs. The blot was then stripped and probed for GAPDH levels as a control for protein loading (n = 2).