TCRγ gene rearrangement and expression in NK cells. (A) Southern hybridization with Jγ1-specific oligonucleotide probe of genomic PCR (left) or RT-PCR (right) of IL-2–activated adult and neonatal NK cells to test for rearrangement of TCRγ locus and expression of rearranged TCRγ genes. Thymocytes are the positive control, and fibroblasts (L cells) are the negative control. Nkg2a PCR and glyseraldehyde-3-phosphate dehydrogenase (Gapdh) RT-PCR were used as control. (B) NK-cell DNA from adult Rag2^–/– was tested by genomic PCR for Vγ2-Jγ1 rearrangement as in panel A. (C) Sequences of neonatal NK-cell RT-PCR products for Vγ2-Cγ1 transcripts. Only the sequences at the junction of Vγ2-Jγ1 are shown. The in-frame stop codon in Vγ2 is underlined.