Increase of intracellular cAMP in primary human T cells inhibits production of both Th1- and Th2-type cytokines.

Cultures of primary human T lymphocytes were established as described in the legend to Figure 1B using concentrations of forskolin and IBMX, which completely inhibited TCR/CD3 plus CD28–mediated proliferation, but only slightly inhibited PMA plus CD28–mediated proliferative responses. Supernatants were collected at 24, 48, and 72 hours of culture and the levels of the indicated cytokines were examined by ELISA. The time interval at which the maximum production was detected in anti-CD3 plus anti-CD28 culture is shown for each cytokine; that interval was 24 hours for IL-2, 48 hours for IL-4, and 72 hours for IFN-γ and IL-4. Results are representative of 4 experiments. Error bars indicate range of responses generated in these experiments.