Figure 4: The procedure of enzyme-linked immuno-spot (ELISpot) assay. To detect CTL responses against HCV, we performed IFN--based ELISpot assay. CD8+ cells and monocytes were separated from peripheral blood samples by magnetic beads (MACS system; Miltenyi Biotec, Bergisch Gladbach, Germany) and used as effector cells and antigen-presenting cells, respectively. These cells with synthetic HCV peptides were incubated for 18 h at C in 5% CO2 atmosphere. Using an ELISpot reader (KS ELISPOT compact; Carl Zeiss, Oberkochen, Germany), the number of spot-forming cells (SFCs) per well was counted.