Figure 1: Classical model of interferon signaling. A. Signaling through the transcription factors STATs. Binding of the cytokine to its cognate receptor begins a series of interactions that through the participitation of the tyrosine kinases, JAK1 and JAK2, result in the phosphorylation of STATs. STATs are then translocated to the nucleus to activate specific genes. B. Alternate IFNγ signaling pathways. Multiple pathways through MAP kinase and IKK/NF-κB signaling can activate the genes involved. See ref. 7 for details.