Circulating CD4⁺CD8⁺ cells in HCV infection. (A-B) Representative dot plot of IFN-γ (A) and TNF-α (B) production by CD4⁺CD8⁺ cells and CD4⁺ and CD8⁺ cells after stimulation with HCV overlapping peptides. (C-D) Percentage of HCV-specific, IFN-γ-producing cells (C) or TNF-α-producing cells (D) in each cell subset for all patients tested. The bars indicate the cumulative response to all HCV peptide pools. nt indicates not tested.