Figure 9

T-lymphocytes. Correlating with a delayed detection of cytokines and chemokines in the supernatants of lung homogenates (Figs. 5 and 6), CD4⁺ and CD8⁺ T-cell infiltration was delayed in the lungs of aged animals (white squares) (A and B). However, up-regulation of CD69 was similar in aged and adult animals (C and D), which suggested non-specific up-regulation of this marker by these cells. Confirming this, activated influenza specific cells were detected only after day 9 post-infection (E and F). Plots A to D represent cumulative results of two different experiments. The arithmetic means (± SEM) of the number of cells (A and B) or percentages (C and D) at each time point (4-6 mice per time point) were plotted. In panels E and F, 5 mice per time point were assayed bars represent the arithmetic mean (± SEM). Stars indicate statistical difference between aged and adult animals. *P < 0.05. **P < 0.01. ***P < 0.001.