Extended duration of IL-7 treatment during the clonal contraction phase results in durable enhancement of the quality of LCMV-specific CD8 T cells. Mice were infected with LCMV-Clone 13 and treated with either IL-7 (●) or PBS (▴) between days 8 and 30 PI, as described in Figure 3. At days 8, 31, 44, and 90 PI, LCMV-specific CD8⁻ and CD4⁻ T-cell responses in the spleen were assessed by flow cytometry. LCMV epitope–specific, triple cytokine (IFNγ, TNFα, and IL-2)–producing cells were enumerated by intracellular staining (A-B). (A) The percentages of triple cytokine–producing cells of epitope-specific CD8 or CD4 T cells at different days PI. (B) The total numbers of triple cytokine–producing epitope-specific CD8 or CD4 cells. *P ≤ .05; **P ≤ .005; ***P ≤ .001.