The effect of dibutyryl guanosine cyclic monophosphate (db-cGMP) on proliferation of an interleukin-2 (IL-2)-dependent T-cell line was investigated. Dibutyryl cGMP added to HT-2 cell cultures without IL-2 or in the presence of an optimal IL-2 concentration (60 U/ml) had no effect on proliferation. The same amount of db-cGMP (10-5M) added to cultures in the presence of suboptimal amounts of IL-2 (3-6 U/ml) produced significant increases in proliferation. In contrast, db-cAMP caused substantial inhibition of HT-2 cells cultured with IL-2. Similar effects were observed using human T-cell blasts produced after 72 h stimulation with phytohemagglutin. These results suggest that cyclic GMP may play a role in the cellular response of IL-2 responsive cells to IL-2.
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