Expression of IL-18 mRNA and secretion of IL-18 are reduced in monocytes from patients with atopic dermatitis

Background: IL-18 has been found to be an IFN-gamma -inducing factor that p lays an important role in T(H)1 cell activation. Recently, IL-18 has also b een found to enhance a T(H)2 cellular response in a specific setting. Objective: The aim of this study was to elucidate the role of monocytes and soluble factors, with special focus on IL-18, in the pathogenesis of atopi c dermatitis (AD). Methods: The release of cytokines front PBMCs and purified monocytes was me asured through use of ELISA; mRNA expression was evaluated by RT-PCR. The r esults from patients with AD were compared with those from healthy controls . Results: IL-18 secretion was reduced in both unstimulated and lipopolysacch aride-stimulated monocytes from patients with AD. The mRNA expression of IL -18 and IL-lp-converting enzyme was significantly reduced in unstimulated m onocytes from patients with AD (P <.03 and P <.01, respectively). Patients with AD had an elevated secretion of prostaglandin E-2 (PGE(2)) from unstim ulated PBMCs (P <.001). The anti-PGE(2) antibody reversed the suppressive e ffect of PGE(2) on IL-18 secretion in unstimulated PBMCs from patients with AD. Conclusions: Decreased IL-18 production, together with a significantly redu ced IL-18 and ICE mRNA expression in unstimulated monocytes and elevated PG E(2) secretion from PBMCs, was associated with the pathogenesis of AD.