Figure 2.

Type I IFN but not type III IFN mature DC to proliferate CTL and NK cells. If type III IFNs mainly act on DCs, CTL and NK cells cannot be activated as effectors for the elimination of HCV-infected hepatocytes. Instead, ISG20 and RNase L induced in hepatocytes by IFN-lambda participate in elimination viral RNA of HCV-infected cells. IFNLR is a receptor for IFN-lambda, but unlike IFNAR, this receptor cannot activate CTL and NK cells. Thus, ISG20 and RNaseL act as major effectors in hepatocytes to suppress viral infection via IFN-lambda. Once type I IFN is induced, TLR3 is up-regulated in DC and DC-mediated cellular immunity is evoked to kill virus-infected cells.