Suppression of JAK3 expression by PGE₂/IBMX 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 PGE₂/IBMX for 24 hours and then stimulated with IL-2 for various times before performing Western blot using antibodies to JAK1, JAK3, c-Myc, c-Jun, and Bcl-2. (B) Densitometry scan of immunoblot in (A) showed that after 24 hours of coculture with 10 μmol/L PGE₂/10 μmol/L IBMX JAK3 was reduced by 57%, which remained suppressed during IL-2 stimulation (81% reduction). In PGE₂/IBMX-treated cells, the IL-2–dependent induction of c-Myc was partially suppressed (54% reduction), whereas the induction of c-Jun was suppressed by 96%. In contrast, PGE₂/IBMX had little effect on the increase in Bcl-2 induced by IL-2 stimulation (6% reduction, 24 hours). (C) Primed cells were stimulated with IL-2 (1,000 U/mL) in medium alone or medium supplemented with PGE₂/IBMX. Proliferation was assessed after 3 days of culture by measuring the uptake of [³H] thymidine. Representative data are presented (n = 3).