PDE4B expression in normal and malignant B lymphocytes. (A-B) Quantitative real-time RT-PCR analyses of PDE4B isoforms in highly purified mature B-cell populations (naive, centroblasts, centrocytes, memory cells) and DLBCL cell lines. The expression of the target and control genes was calculated by entering the real-time RT-PCR CT values (average of triplicates) into a standard curve generated from plasmid DNA of known concentrations. Data represent PDE4B isoform copy number normalized to control gene for each sample (A, PDE4B2 only; B, PDE4B1, B2, and B3). (C) PDE4B protein expression in DLBCL cell lines. Cells were either untreated (-) or treated with 40 μM forskolin (Frs) and 10 μM rolipram (Rol) for 6 hours (+). Whole-cell lysates were immunoblotted with a pan-PDE4B antisera. PDE4B2 exhibits the characteristic up-regulation following an increase in intracellular cAMP. PDE4B1 and B3 comigrate at approximately 105 kDa, whereas the PDE4B2 doublet is 78 to 84 kDa. Size markers are indicated on the left in kilodaltons.