Given that interferon (IFN) signaling has been shown to control tissue tropism and pathogenicity of PV (Ida-Hosonuma et al., 2005), we further investigated the kinetics of RNA levels of IFN-related and -stimulated genes, in response to PV-3 infection by quantitative RT-PCR (Figure 4C). This evidence concerns the gene IFNA1 and acquired polycythemia vera.