Gag-specific CD8+ T-cell responses in the acute phase. PBMCs at week 2 were stimulated with p55, and specific induction of IFN-γ, TNF-α, IL-2, MIP-1β, and CD107a in CD8+ T cells was examined. (A) Frequencies of total Gag-specific CD8+ T cells. (B) Percentages of cells exhibiting Gag-specific induction of single or multiple marker cytokines in total Gag-specific CD8+ T cells. See the legend to Fig. 2 for symbols. (C) Frequencies of Gag-specific CD8+ T cells exhibiting Gag-specific induction of ≥3 marker cytokines (polyfunctional; left) or ≥4 marker cytokines (highly polyfunctional; right) in total CD8+ T cells.