Although significantly higher IgG1 titers were detected in IL-2 CYT-IVAC vaccinated mice compared to wild-type vaccinated mice, the IgG2a isotype remained the predominant influenza specific isotype detected in serum samples collected from mIL-2 or mIL-4 CYT-IVAC vaccinated mice, indicating a skewing towards a Th1 immune response. This evidence concerns the gene IL2 and influenza.