Thymectomy results in the perturbation of the NP-specific repertoire of CD8 T cells in young C57BL/6 mice. Young naive C57BL/6 mice were thymectomized, rested for 7 mo, and then intranasally infected with influenza virus. Lung tissue was harvested from both groups of mice 11 d after infection. The frequencies and absolute numbers of CD8 T cells detected in the lungs of individual infected mice are shown in A and B. The frequencies and absolute numbers of CD8 T cells positive for the influenza virus MHC class I tetramers NP (NP_366-374/D^b), PA (PA_224-233/D^b), or PB1 (PB1_703-711/K^b) detected in the lungs of individual infected mice are shown in C and D. Open and closed symbols represent individual thymectomized (ThyX) and control mice, respectively (n = 5 for each group). Bars indicate the medians calculated from the groups of control and thymectomized mice. Significance was assessed using the Mann-Whitney rank test (two-tailed, 95% confidence).