VAF347 induces AhR signaling. (A) VAF347 and TCDD, but not VAG005, induce the expression of CYP1A1 mRNA in peripheral blood monocytes. RNA was analyzed by qRT-PCR after a 4-hour incubation period with the compounds alone or in the additional presence of IL-4 and GM-CSF. The expression level of CYP1A1 relative to the housekeeping gene eF-1α is shown. The error bars indicate SD. P values indicate statistical significance determined by a paired Student t test. (B) VAF347 and TCDD, but not VAG005, inhibit IL-6 production by maturing DCs. Monocyte-derived DCs were activated with a cocktail containing GM-CSF, IFN-γ, TNF-α, anti-CD40 mAb, and goat anti–mouse IgG to crosslink the anti-CD40 mAb. The levels of IL-6 were measured in the supernatants by ELISA. (C) VAF347 and TCDD, but not VAG005, inhibit DC-mediated T-cell proliferation. Immature monocyte-derived DCs were pulsed with KLH and subsequently cocultured with autologous CD4⁺ T cells. The primed T cells were restimulated for 4 additional days with fresh antigen-pulsed DC before T-cell proliferation was measured by tritiated thymidine incorporation.