Evaluation of heterosubtypic influenza A/H1N1-specific CD4+ and CD8+ T-cell immunity among influenza A/H3N2-infected patients IFN-γ: interferon-γ; TNF-α: tumor-necrosis factor-α; IL: interleukin. Results were expressed as number of cytokine-producing CD4+ cells/106 CD4+ T-cells or CD8+ cells/106 CD8+ T-cells. For data presentation, cell frequencies labelled as TNFα+, IFNγ+, IL2+ or IL4+ were cells producing the given cytokine, regardless of the production of other cytokines. The upper edge of the box represents the median value, and the error bars represent the interquartile range. Black and green dots represent individual frequencies in influenza A/H3N2-infected patients at influenza diagnosis and Day 28, respectively.