Quantification of gene transcription by semiquantitative RT-PCR in resting and Il-2–stimulated primary human NK cells. RT-PCR of β-actin, TRAIL-R1, TRAIL-R3, and TRAIL-R4 was performed by using the following cDNA dilutions: 1/8, 1/20, 1/100, 1/500, 1/2500 (lanes 1-5, respectively). RT-PCR of TRAIL-R2 was performed by using the following cDNA dilutions: 1/20, 1/100, 1/500, 1/2500, 1/12 500 (lanes 1-5, respectively). Lane 6 is RT-PCR negative control.