Murine models of aging have been shown to have qualitatively and quantitively impaired anti-influenza immune responses: aged lungs exhibit altered myeloid cell recruitment and function;8,9 lower titers of neutralizing antibodies;10 and delayed and diminished recruitment of CD4 and CD8 T cells to the lung during infection, which results in delayed viral clearance11–13. This evidence concerns the gene CD4 and influenza.