Figure 2: Th1 response by influenza-specific memory CD4+ cells. Activated human CD4+ memory cells (CD3+CD4+CD8-CD14-CD45RA-CD56-CD69+) were analyzed for expression of IFN-?, TNF-a, and IL-2. Cells were stimulated with medium-only (NEG), FluZone vaccine (three influenza strains at equivalent concentrations based on viral HA), or SEB. A: Representative density plots with histograms are shown for activated memory CD4+ cells expressing IFN-? (increasing from left to right), TNF-a (left column, increasing from bottom to top), and IL-2 (right column, increasing from bottom to top). Percentages are based on total CD4+ T-cells in each sample and results are shown as the mean standard error (SE) (n = 7). B: Single cytokine populations IFN-?, TNF-a, and IL-2 are shown. C: Double and triple cytokine expressing (IFN-?/IL-2, TNF-a/IL-2, IFN-?/TNF-a, IFN-?/TNF-a/IL-2) CD4+ T-cell populations are shown. Stimulated samples were compared to their unstimulated counterparts using Mann-Whitney statistical tests.