Interestingly we observed significantly higher numbers of CD4+ T cells in the spleen (p = 0.0272) and in the lungs (p = 0.0048) of infected ferrets, and a trend toward higher numbers of CD8+ T cells in the lungs (Figures 5B,C), indicating a T cell response to H7N9 infection at a key site of infection. This evidence concerns the gene CD4 and infection.