Figure 2: Destruction of HCV-infected hepatocytes by CTLs. ( 1 ) Immature myeloid dendritic cells (iDC) take up hepatitis C virus antigens (HCV Ag) in the liver. ( 2 ) The DCs move to a draining lymph node. ( 3 ) Matured DCs activate naïve helper T (Th) cells efficiently through stimulation with HLA class II, costimulatory molecules (CD80 and CD86), and cytokines such as IL-12. The stimulated Th cells, in turn, activate DCs by expressing CD40 ligand and secreting TNF- 𝛼 . IL-12 produced by myeloid DCs differentiates these stimulated Th cells towards Th1 cells. Naïve cytotoxic T lymphocytes (CTLs) recognize the HCV Ag presented on the DCs. IL-2 and IFN- 𝛾 secreted by activated Th1 cells induce the activation and proliferation of the HCV-specific CTLs. ( 4 ) The stimulated HCV-specific CTLs leave the lymph nodes and move toward the liver. ( 5 ) They recognize HCV antigens together with HLA class I on the surface of HCV-infected hepatocytes, and try to eradicate HCV by killing the infected hepatocytes. Abbreviated terms: Th1 cell, type 1 helper T cell; mDC, myeloid dendritic cells; CTL, Cytotoxic T lymphocyte; CD, cluster of differentiation; CD40L, CD40 ligand; TCR, T-cell receptor; HLA, human leukocyte antigen; TNF, tumor necrosis factor; IL, interleukin; IFN, interferon.