IHC-FACS analysis showed that the frequency of CD8+ cells and CD163+ macrophages in lung tissue increased dramatically in both young (6.5% and 4.1%, respectively) and old RMs (5.9% and 4.8%, respectively) after infection compared with the healthy young (3.1% and 2.8%, respectively; p < 0.05) and old groups (2.9% and 2.8%, respectively; p < 0.05). This evidence concerns the gene CD8A and infection.