Effect of IL-7 treatment during early contraction phase on the CD8 T-cell response. Cohorts of LCMV-Clone 13–infected mice were treated daily with either IL-7 or PBS between days 8 and 15 PI, as depicted by the shaded area (A). At days 8 (before IL-7 therapy), 16 (1 day after completion of therapy), and 40 (25 days after cessation of IL-7 therapy) PI, the numbers of naive (CD44^lo) and activated (CD44^hi) CD8 or CD4 T cells (B) and LCMV epitope-specific, IFNγ-producing CD8 or CD4 T cells (C) in IL-7- (●) or PBS (▴)-treated mice were quantified by flow cytometry. Data for each time point were obtained from 4-5 mice per group. *P ≤ .05; **P ≤ .005.