These down-regulated genes include p21, 14-3-3, PERP, FAS, DR4/5, PIG3, BAX, Bcl-XL, PAI-1 and PCNA. For p21 (CDKN1A) for example, the n-fold mRNA changes measured were -1.81, -2.0 and -1.85 for H3N2, H5N1 and H7N1 infections, respectively. Here, PCNA is linked to infection.