CD4 and influenza: Recent animal and human studies of T-cell responses to influenza infection or vaccination have examined a range of topics applicable to influenza vaccines, including intranasal CD4 T-cell elicitation and dose- and preexisting antibody-dependent CD8 T-cell activation [41], associations between specialized T-cell effectors and age [42,43], and the function and activation of CD8 and memory T cells in the lungs [44].