In birds and mammals, influenza-specific CD8+ cytotoxic cells become activated and produce IFNγ during infection in response to the engagement of their T cell receptors with influenza-derived peptides in the context of MHCI on the surface of antigen presenting cells (APC) (Rock et al., 1990; Suarez and Schultz-Cherry, 2000; Novak et al., 2001; Subbarao and Joseph, 2007). This evidence concerns the gene CD8A and influenza.