Fig. 1.

IFN-γ^−/− and Prf^−/− mice mount adaptive immune responses with increased frequencies of anti-VACV memory CD8⁺ T cells. B6, IFN-γ^−/−, and Prf^−/− mice were infected with 10⁶ PFU VACV i.p.; ≥30 dpi, sera and spleens were collected, processed, and analyzed. (Top) Representative flow cytometry plots show the percentages of DimerX staining. U, uninfected. (Bottom) Bar graphs show summary data for the percentages of DimerX staining. Data are results of four independent experiments (except for Prf^−/− mice, with two independent experiments) with pooled spleens from five mice. Means ± SEM are shown. Asterisks for infected B6 mice represent P values for comparisons to uninfected B6 mice. Asterisks for IFN-γ^−/− and Prf^−/− mice represent P values for comparisons to infected B6 mice. *, P = 0.05; **, P = 0.01; ***, P = 0.001.