Indeed, CD4 and CD8 T cells show age-related changes in function (Maue et al., 2009; Lorenzo et al., 2018; Haynes, 2020), with changes in CD4 T cells during aging (Haynes and Swain, 2012; Lee et al., 2012) influencing both CD8 T function and B cell antibody production in response to influenza (Maue et al., 2009; Toapanta and Ross, 2009; Lorenzo et al., 2018). Here, CD4 is linked to influenza.