WASP expression by RT-PCR in T, B, and NK cells and in monocytes. Approximately 20 ng of the same RNA preparation (that was used in the Northern blot) was reverse transcribed with primers specific for WASP cDNA and PCR amplified (25 cycles). The PCR products were electrophoresed, blotted, and hybridized with the same WASP probe used in Northern blot analysis; the expected size of 900-bp is shown. For control of cDNA quality, PCR amplification with specific primers for the G3DPH sequence was performed (20 cycles) and shown by hybridization with a cDNA radioactive probe (a product of 300 bp). The lane with H₂O represents the PCR-negative control.