Distinct roles of IL-18 and IL-1β in murine model of macrophage activation syndrome.

BACKGROUND:IL-18 and IL-1β play a central role in the pathogenesis of systemic juvenile idiopathic arthritis and its life-threatening complication, macrophage activation syndrome (MAS). OBJECTIVES:This study aimed to clarify the role of IL-18 and IL-1β in the pathogenesis of MAS. METHODS:We developed a mouse model to evaluate the role of each cytokine with Toll-like receptor 9 stimulation after continuous infusion with IL-18, IL-1β, and a combination of both for 7 days. The symptoms and laboratory findings were compared among the IL-18, IL-1β, and combination (IL-18+IL-1β) groups. RESULTS:Body weight was significantly decreased in the IL-1β and combination groups. Splenomegaly was observed in all groups, whereas hepatomegaly was noted in the IL-18 group only. Decreased T-cell numbers, anemia, and thrombocytopenia were observed in the combination group. IFN-γ, CXCL9, and IL-12A mRNA levels were upregulated and IL-10 mRNA levels in the spleen were downregulated in the IL-18 group. Hepatomegaly and splenomegaly in the IL-18 group were observed in a dose-dependent manner. TNF-α, CXCL9, and IL-12A mRNA levels were upregulated only in those mice with extremely elevated plasma IL-18 levels. CONCLUSION:IL-18 and IL-1β have distinct roles in the pathogenesis of MAS. Dual blockade of IL-18 and IL-1β might be necessary to treat MAS.