Figure 2

The cytokine response of influenza NP-specific CD4 T cells is delayed in aged compared with young mice. Lung airway cells obtained by bronchoalveolar lavage from young and aged mice were analyzed at days 8, 10, 12 and 14 following i.n. infection with 3,000 EID₅₀ ×-31 for production of cytokines following in vitro stimulation with the NP_311–325 peptide. Cytokine-producing cells (IFN-γ, TNF-α and/or IL-2) within the CD4⁺CD44^high population were divided into seven subpopulations based on their production of these cytokines in combination (refer to color code at the bottom of Panel B). The relative contribution of each of these subpopulations to the responding T cell population was determined as depicted in the pie charts in panel A. The bar charts in panel B show the frequency of each cytokine subpopulation out of the total responding CD4 T cell population. Data are representative of 2 independent experiments with 5–8 mice per time point.