Low IFNL4 induction during PAMP stimulation and viral infection. (A and B) Schematic of IFNL4 mRNA exhibiting intron retention (IR), compared with the known protein-coding isoforms of IFNL4. (C–H) Gene expression kinetics of IFNL3 and IFNL4 isoforms measured by qPCR using custom made TaqMan probes in Huh7 (C), HepG2 (D), HeLa (E), and HEK293 (F) cells upon stimulation with HCV PAMP, and DCs derived from THP1 (G) and MUTZ-3 (H) cell lines stimulated with poly(I:C). (I–J) Gene expression of IFNL3 and IFNL4 isoforms in primary human hepatocytes, heterozygous (I) or homozygous (J) for the ΔG variant, stimulated with poly(I:C). (K–M) Gene expression of IFNL3 and IFNL4 isoforms in HepG2 cells infected with DenV (K), WNV (L), and SeV (M). Experiments are representative of two to three independent experiments (C–H and K–M); experiments on PHHs (I–J) were performed on two biological replicates for each genotype.