IFN-α inhibits C1q production in DCs inducing DC maturation. DCs were differentiated in regular medium (“Materials and methods”) in the presence or absence of IFN-α. Culture media were collected during culture and tested for C1q (A) (results shown are mean ± SD of 1 of 3 similar experiments [with 3 different donors] performed in triplicate). *P < .0001 compared with immature DCs (2-way ANOVA of 3 experiments). At day 7, DCs were harvested and analyzed using FACS (B). White histograms indicate isotype control. After extensive washing, day-7 DCs differentiated in the absence or presence of IFN-α were cultured in normal DC medium for 48 hours (C). Media were collected at different time points. Results are from triplicate experiments in 1 donor and are representative of those from 3 different donors. Error bars represent SD.