To explore the expression of IL-18 in patients with active lupus nephritis(LN) and the inhibitory effects of immunosupressive agents FK506, cyclosporin A (CsA) and dexamethasone(DEX).Peripheral blood samples were collected from 16 LN patients and 10 health volunteers and cultured with or without PHA/LPS, PHA/LPS+FK506, PHA/LPS+CsA and PHA/LPS+DEX for 24 hours. The IL-18 level in cultured supernatants and the IL-18 mRNA expression in cultured whole blood cells were detected by ELISA and semi-quantitative RT-PCR respectively, and the inhibitory effects of FK506, CsA and DEX on IL-18 expression were investigated.The expression levels of IL-18 mRNA and its protein in whole blood cell cultures from LN patients were higher than those in normal control group (P0.01) either spontaneously or after stimulation with LPS/PHA. FK506, CsA and DEX suppressed significantly the expressions of IL-18 mRNA and its protein (P0.001) in LPS/PHA-stimulated whole blood cell from LN patients. The inhibitory effects of FK506, CsA and DEX on the IL-18 protein expression in LN patients were stronger than that in normal control group (P0.01 or P0.05).IL-18 may play an important role in the pathogenesis of LN and inhibition of IL-18 production may be an useful way to treat LN.