TLR7 and influenza: Figure 2B depicts the cytotoxic activity of influenza-specific CTLs against peptide-loaded target cells. Immunization of wt mice with WIV induced high levels of cytotoxicity in these animals. In contrast, lysis of target cells was not detected in TLR7−/− mice after immunization with WIV. When CTLs were primed by infection with live virus, both wt and TLR7−/− mice displayed similar levels of cytotoxicity against peptide-loaded target cells.