Increases in intracellular levels of cAMP mimic inhibitory effects of extracellular adenosine on CD25 expression. (A) Effect of 50 μmol/L dBcAMP and 50 μmol/L IBMX on CD25 level on TCR transgenic lymphocytes stimulated with 1 μmol/L cytochrome c for 8 hours. The experiment was performed as described in the legend to Fig 2. The histogram represents estimation of the effects of dBcAMP and IBMX on TCR-triggered CD25 upregulation among TCRαβ⁺ cells. (B) Effect of 50 μmol/L dBcAMP on CD25 level on 4 μg/mL con A-stimulated splenocytes. DBA-2 splenocytes were stimulated with con A for 8 hours and the percentage of CD25⁺ cells in the T subset was shown in the plots. The histogram represents estimation of effects of dBcAMP on con A-triggered CD25 upregulation among TCRαβ⁺ cells.