Mice were infected with LCMV Armstrong and splenocytes were analyzed 7 days later. Shown are (left) numbers of splenocytes and T cells and (right) numbers of MHC class I tetramer+ CD8 + T cells from mice of the indicated genotypes (WT, n=12, Cy11b1foxN1-Cre, n=11; lckCre alone, n=6, Cyp11b1lck-Cre, n=6). Data represent the mean ± SEM. *P < 0.05, **P < 0.005.