A trans-dominant negative AhR protein blocks the function of VAF347 in MM1 cells. Loss of biologic activity of VAF347 and TCDD to block IL-6 synthesis in AhR515 overexpressing MonoMac1 cells. Top row: qRT-PCR of IL-4+GM-CSF–induced IL-6 RNA after 24 hours in control (vector) or AhR515-expressing cells; middle row: IL-6 protein was measured in the supernatants from the same cells; bottom row: similar effects as for VAF347 are shown with TCDD on IL-6 mRNA. Error bars represent SD.