The activation phenotype of T cells in the lungs was investigated at 0, 8, 9, 12, and 15 days p.i. Both CD8+ and CD4+ T cells were activated during infection, resulting in an increased proportion of effector T (Teff) cells and a decreased proportion of naive T (Tnaive) cells (Figures 2A, B; Supplementary Figure 3). This evidence concerns the gene CD4 and infection.