IL4 and influenza: On the other hand, it is well-known that the cell-mediated immune parameters, including IgG2a, Th1-kind (IFN-γ) and Th2-kind (IL-4) cytokines, play a critical role in virus clearance, but conventional inactivated influenza vaccines commonly lack the ability to induce cytotoxic T-lymphocyte (CTL) responses [1].