This peptide is amino acids 311 to 325 fragment of the influenza virus nucleoprotein (NP). This bona fide MHC class II restricted epitope from influenza virus was used to study the host immunoresponse during the infection. This peptide elicits the strongest gamma interferon (IFN-gamma) production in the intracellular cytokine assays. It does not stimulate CD8 T-cells in mice.