CLL cells contain transcripts for PDE 1B1, PDE4A, and PDE4B. PCR was performed on cDNA derived from WMC (purified from a normal donor) or CLL cells for PDE1, PDE3A, PDE4A, and PDE4B. The cDNA used in the PCR in the bottom three panels was derived from leukemic cells from three different patients purified by positive selection for CD19 expression. The lowest band in the MWM lane on the left in the upper panel is 603 bp. Expected PCR product sizes for PDE1, 3A, 4A, and 4B are 430, 340, 461, and 470 bp, respectively.