Rolipram blocks cAMP catabolism in both sensitive and resistant lymphoid populations. One million cells from the leukemic cells of two CLL patients (top; [▧], patient no. 1; [▪], patient no. 2), magnetic bead-purified CD19⁺ B cells (middle; [▧], resting; [▪], stimulated), or IL-2 supplemented WMC (bottom panel) were cultured with media, 10 μmol/L rolipram, 40 μmol/L forskolin, or both agents for 2, 6, or 24 hours, as indicated. cAMP content was determined by radioimmunoassay. In the case of the CD19⁺ cells, the cells were first cultured in media or Fab′₂ anti-IgG/M for 30 minutes before treatment with rolipram or forskolin. Data are the mean of duplicate wells for each condition and are representative of two experiments with similar results.