Both, type-I and -III IFNs are directly induced through sensing of viral infection via pattern recognition receptors such as Toll-like receptors (TLRs), retinoic acid-inducible gene 1 or melanoma differentiation-associated protein 5.17,51 For example: CpG-DNA (TLR-9 agonist) induces the expression of IFN-α, -β and IFNL1-3 in plasmacytoid DCs.27,33,46,47,55 Lipopolysaccharide (TLR-4 agonist) and poly(I:C) (TLR-3 agonist) induce IFN-β and IFNL1–3, but not IFN-α in myeloid DCs.33 Poly(I:C) can also induce IFNL4 expression in the appropriate genetic background. Here, IFNL1 is linked to viral infectious disease.