First-strand cDNA was synthesized with 500 ng of purified RNA using SuperScriptII (Invitrogen) and a mixture of T21 and random nonamer primers (Metabion) following the instructions for the reverse transcription reaction recommended for the Quanti-Tect SYBR Green PCR Kit (Qiagen). Real-time quantitative PCR was performed on an ABI Prism 7700 real time cycler. The relative expression of the targets IFNa2 (Interferon alpha 2) and IFNb1 (Interferon beta) were normalized to that of two reference genes: SDHA (Succinate dehydrogenase alpha subunit) and PPIA (peptidylprolyl isomerase A). Finally a mean of the fold change of the target versus each of the reference genes was taken as the final value.