Interferon-α (IFN-α) down-regulates the expression of A20 mRNA in myeloid dendritic cells (mDCs) cultured in vitro. The mDCs purified from treatment-naive patients (n = 10) and healthy subjects (n = 10) were cultured in the presence of poly-IC, IFN-α, or IFN-α/poly-IC. A20 mRNA levels were detected by quantitative real-time PCR. (a) A20 mRNA expression in mDCs isolated from treatment-naive patients and healthy subjects and then treated for 12 hr with polyI:C (50 μg/ml). (b) A20 mRNA expression in mDCs isolated from healthy subjects and treatment-naive patients and then cultured with IFN-α (1000 U/ml) for 48 hr. (c) Myeloid DCs isolated from healthy subjects and treatment-naive patients and then cultured with IFN-α (1000 U/ml) for 48 hr. PolyI:C (50 μg/ml) was added to the culture for the final 12 hr. Each symbol represents an individual subject. *P < 0·05, **P < 0·01, ***P < 0·001, ns: not significant.