To analyze whether NF-kB activation is sufficient for SOCS-3 gene induction we stimulated cells with IL-1b ( Figure S2A ) or TNFa ( Figure S2B ) that are both strong activators of the transcription factor. While mRNA levels of IL-6, a strictly NF-kB dependent cytokine, are strongly elevated, SOCS-3 gene transcription is not significantly induced. Under the assumption that these cytokines do not additionally induce counteracting processes one can conclude that NF-kB is required, yet not sufficient for the induction of SOCS-3. Thus viral induction of SOCS-3 may require additional factors that are only active in virus-infected cells. Furthermore, these results rule out a potential role of virus-induced IL-1b or TNFa in the induction of SOCS-3. This is supported by the observation that neither expression of IL- 