Figure 8A shows that infection by mCMV results in the anticipated reduced level of newly transcribed RNA of the sterol biosynthetic pathway genes. Next we sought to test whether the Tyk2 receptor-signaling component is required for the type I interferon-dependent down-regulation of the sterol pathway. For these experiments we used tyk2−/− macrophages and observe an almost complete abrogation of the transcriptional down-regulation by mCMV infection (Figure 8B). The gene discussed is TYK2; the disease is infection.