Fig. 11.

Schematic diagram of the signaling pathways contributing to SHP-1 induction. Interferons and cytokines that result from viral infections can activate either promoter I or II of the SHP-1 gene. In particular, IFN-γ and IFN-β can activate STAT-1, resulting in the induction of IRF-1 and subsequent induction of the SHP-1 promoter I transcripts. In contrast, IFN-β and IL-6 can activate STAT-3, resulting in the induction of promoter II transcripts. Consequently, the increased SHP-1 activity is expected to counteract viral replication and inhibit cytokine signaling.