CD8A and infection: However, in our experiments, contraction in the number of CD8 T cells in the respiratory airways (Figure 2) or lungs (data not shown) did not occur until after 8 days after HK483 infection (dose of 18 PFU/mouse or 10 MLD50); the number of CD8 T cells in the BAL of HK483-infected mice was lower at day 9 PI, when compared to those in HK486-infected mice.