Suppression of JAK3 expression by forskolin and dbcAMP correlates with the inhibition of IL-2–dependent signaling pathways for induction of c-Myc and c-Jun. (A) After 3 days of priming, T cells were cultured with forskolin (100 μmol/L) or dbcAMP (1 mmol/L) for 24 hours and then stimulated with IL-2 for various times before performing Western blot using antibodies to JAK1, JAK3, c-Myc, and c-Jun. (B) Densitometry scan of immunoblot in (A). After 24 hours of coculture with forskolin (100 μmol/L) or dbcAMP (1 mmol/L), JAK3 was reduced (43% and 49% correspondingly) and remained suppressed during IL-2 stimulation (79% and 94% reduction correspondingly). IL-2–dependent induction of c-Myc was suppressed by 67% (forskolin) and 61% (dbcAMP). The induction of c-Jun was suppressed by 77% (forskolin) and 69% (dbcAMP).