Surface expression of DC-SIGN increases as monocytes differentiate into iDCs. PBMCs were isolated by density gradient centrifugation and cultured for 3 days in the presence of DC growth factors. Cells were collected on each day and incubated with anti–DC-SIGN mAb, followed by incubation with a secondary Ab conjugated to Alexa Fluor 488 and analysis by flow cytometry. (A) Percentage of positive cells. (B) Mean fluorescence intensity (MFI; n = 3).