Protection against RNA-induced liver damage by myeloid cells requires type I interferon and IL-1 receptor antagonist in mice.

Unlabelled: Cell types and mechanisms involved in type I interferon (IFN)-mediated anti-inflammatory effects are poorly understood. Upon injection of artificial double-stranded RNA (poly(I:C)), we observed severe liver damage in type I IFN-receptor (IFNAR) chain 1-deficient mice, but not in wild-type (WT) controls. Studying mice with conditional IFNAR ablations revealed that IFNAR triggering of myeloid cells is essential to protect mice from poly(I:C)-induced liver damage. Accordingly, in poly(I:C)-treated WT, but not IFNAR-deficient mice, monocytic myeloid-derived suppressor cells (MDSCs) were recruited to the liver. Comparing WT and IFNAR-deficient mice with animals deficient for the IFNAR on myeloid cells only revealed a direct IFNAR-dependent production of the anti-inflammatory cytokine interleukin-1 receptor antagonist (IL-1RA) that could be assigned to liver-infiltrating cells. Upon poly(I:C) treatment, IFNAR-deficient mice displayed both a severe lack of IL-1RA production and an increased production of proinflammatory IL-1β, indicating a severely imbalanced cytokine milieu in the liver in absence of a functional type I IFN system. Depletion of IL-1β or treatment with recombinant IL-1RA both rescued IFNAR-deficient mice from poly(I:C)-induced liver damage, directly linking the deregulated IL-1β and IL-1RA production to liver pathology.

Conclusion: Type I IFN signaling protects from severe liver damage by recruitment of monocytic MDSCs and maintaining a balance between IL-1β and IL-1RA production.