Close association between the cytotoxic activity of HIV-1-specific CD8⁺T cells and their ability to produce both interferon-γ and TNF-α following viral antigen exposure. Correlation between the epitope-specific cytotoxic activity of HIV-1-specific CD8⁺ T cells and the corresponding proportion of HIV-1-specific CD8⁺ T cells producing both interferon-γ and TNF-α (A) or interferon-γ but no TNF-α (B) following antigenic stimulation. Dashed lines indicate the 95% confidence intervals of the regression line.