Expression of type 1 ADO receptors by CLL cells. Purified leukemic cells from CLL patients were analyzed for the expression of the 4 known ADO receptors. (A) RT-PCR data on the mRNA levels of A1, A2A, A2B, and A3 receptors. n = 35. (B) A2A levels in CLL patients (n = 35) were compared with sex- and age-matched individuals without evidence of CLL (n = 8). (C) Ligation of A2A with the selective agonist CGS21680 (10μM, for 30 minutes at 37°C) induces a significant increase in intracellular cAMP levels in basal conditions and on treatment with CpG/IL-2 (1 μg/mL and 100 IU/mL, respectively) for 48 hours. n = 8. (D) RT-PCR analysis of A2A expression in freshly purified CLL cells (basal) or in cells cultured for 48 hours with or without CpG/IL-2. n = 9. The Mann-Whitney U test was used to determine statistical significance. CGS indicates CGS21680.