Adenosine enhances cytosolic cAMP levels in mature PDCs. Freshly isolated PDCs or CD40L trimer–activated PDCs (24 hours) were incubated with 100 μM adenosine in the presence of rolipram. After 30 minutes, cAMP levels were measured in cell lysates by enzyme immunoassay (EIA). Data are expressed as n-fold increase of cAMP levels and represent mean ± SEM of 4 different donors. *P < .05.