TNF and viral infectious disease: We tested the ability of HLCs to respond to ligands for PRRs (RIG-I/MDA5; TLR3, 7, 9); type I IFN, the principle activator of innate anti-viral genes; type III IFN, the main IFN expressed in hepatocytes upon viral infection; and TNF-α, an inflammatory cytokine produced early in viral infection.