In T-cells, IFN-α/β promotes survival of activated CD4+ and CD8+ T cells in vitro (Marrack et al., 1999), CD8+ T cells differentiation and expansion (Curtsinger et al., 2005), and clonal expansion of CD4+ and CD8+ T cells in response to viral infection in vivo (Kolumam et al., 2005). This evidence concerns the gene CD4 and viral infectious disease.