Single-stranded CpG-ODNs inhibit the intracellular TLR3 signaling pathways engaged by poly I:C in DCs. (A) DCs were treated for 1 hour with chloroquine before addition of TLR stimulus, and maturation was measured 48 hours later in 6 different donors. (B) Phosphorylation of the transcription factors IRF-3 and NFκB was detected by Western blot after TLR stimulation for 90 or 15 minutes, respectively. Representative data from 3 independent experiments is shown. (C) Poly I:C–induced secretion of the IRF-3- or NFκB-driven cytokines IFN-α2 (n = 8), IFN-β (n = 5), IP-10 (n = 8), and IL-6 (n = 8), as measured 24 hours after addition of stimuli. Quantity in culture supernatants is depicted in picograms per milliliter as mean ± SEM values. Significant differences comparing with or without addition of ssCpG-ODN were assessed by nonparametric Mann-Whitney 2-tailed test and are indicated by *P < .05, **P < .01, and ***P < .001.