Immunity
Volume 11, Issue 3, 1 September 1999, Pages 359-367
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Article
Caspase-1-Independent, Fas/Fas Ligand–Mediated IL-18 Secretion from Macrophages Causes Acute Liver Injury in Mice

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Abstract

IL-18, produced as a biologically inactive precursor, is processed by caspase-1 in LPS-activated macrophages. Here, we investigated caspase-1-independent processing of IL-18 in Fas ligand (FasL)-stimulated macrophages and its involvement in liver injury. Administration of Propionibacterium acnes (P. acnes) upregulated functional Fas expression on macrophages in an IFNγ-dependent manner, and these macrophages became competent to secrete mature IL-18 upon stimulation with FasL. This was also the case for caspase-1-deficient mice. Administration of recombinant soluble FasL (rFasL) after P. acnes priming induced comparable elevation of serum IL-18 in parallel with elevated serum liver enzyme levels. However, liver injury was not induced in IL-18-deficient mice after rFasL administration. These results indicate a caspase-1-independent pathway of IL-18 secretion from FasL-stimulated macrophages and its critical involvement in FasL-induced liver injury.

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