CD4 and influenza: In mice, adoptive transfer of influenza-specific in vitro-generated memory CD4+ T cells into naive hosts induces a rapid upregulation of pulmonary and systemic inflammatory cytokines, including IFN-γ, IL-12, IL-1, and IL-6, as well as chemokines, such as CXCL9, CXCL10, and CCL2, within 48 h of heterosubtypic influenza challenge.