PRF1 and infection: Large temporal changes in perforin gene expression post-infection were detected by quantitative real-time PCR in spleen (up to + 20 fold at 12 h post-infection, Figure 5a) and gill tissue (9, 11, 8 and 7 fold at 3 h, 24 h, 48 h and 7 days post-infection, respectively, Figure 5c).