T cell subsets (CD4+, CD8+, and TCR-γδ+) were immunophenotyped, and cytokine production was measured by intracellular cytokine staining in order to determine the frequency of IFN-γ–, IL-17A–, and TNF-α–producing influenza-specific T cells (Supplemental Figure 1; supplemental material available online with this article; https://doi.org/10.1172/jci.insight.141088DS1). This evidence concerns the gene CD4 and influenza.