Forskolin and dbcAMP can mimic the effect of PGE₂ and selectively suppress JAK3 expression in naive and primed T cells. (A) CD3⁺ lymphocytes were stimulated with anti-CD3/IL-2 for 24 and 48 hours in the presence of PGE₂(10 μmol/L), Forskolin (100 μmol/L), or dbcAMP (1 mmol/L). Western blotting was performed for JAK1, JAK3, p59^fyn, p56^lck, and STAT5. (B) Primed T cells were cultured with medium, Forskolin (100 μmol/L) or dbcAMP (1 mmol/L) for 48 hours before Western blotting. Representative data from 1 of 4 experiments. (C) Primary CD4⁺ T-cell line (CD4K) and Jurkat T cells were cultured with dbcAMP (1 mmol/L) for 48 hours before Western blotting. Representative data from 1 of 4 experiments are presented.