Full-length KIR transcripts originate from the distal promoter region during NK-cell development. (A) PCR primers were designed to amplify full-length KIR2DL1, -2DL2, and -2DL3 transcripts originating from the distal promoter region. The amplified region begins upstream of the classical transcriptional start site (distal sense) and extends to the stop codon (distal antisense). Open boxes represent KIR gene exons. (B) Mononuclear cells from umbilical cord blood were sorted for specific NK-cell precursor populations based on the expression of the developmental markers CD34, CD7, and CD56. Sorted cells were analyzed for the presence of distal transcripts by RT-PCR using the primers shown in panel A. Control PCRs were carried out using GAPDH primers to confirm the presence of cDNA.