HUMAN CD3-CD16-KILLER-CELLS EXPRESS THE HGATA-3 T-CELL TRANSCRIPTION FACTOR AND AN UNREARRANGED 2.3-KB TCR-DELTA TRANSCRIPT( NATURAL)

In this study we analyzed the Tcell receptor(TcR) delta transcripts ex pressed by CD3-CD16+ cells and we investigated whether these cells exp ressed the hGATA-3 T cell transcription factor and the recombination-a ctivating gene (RAG)-1. Multiple TcR delta transcripts deriving from a n unrearranged TcR delta gene were detected in both polyclonal and clo nal CD3-CD16+ natural killer(NK) cell lines. Two unrearranged TcR delt a transcripts had a size similar to that of the functional TcR delta m RNA (2.3 and 1.3 kb) found in TcR gamma/delta+ T lymphocytes. Sequence analysis of nine different 2.3-kb cDNA clones obtained from NK-derive d polyA+ RNA confirmed that they corresponded to an unrearranged TcR d elta gene. These cDNA were 2343 bp long and their transcription initia tion site was located 814 bp upstream from the Jdelta1 segment. The se quence located upstream of the Jdelta1 segment corresponded to the pre viously reported germ-line sequence. The Jdelta1 segment was correctly spliced to Cdelta; in addition the four Cdelta exons were found to be already assembled. Two polyadenylation sites were present in the four th Cdelta exon. However, only that located at the 3' end appeared to b e utilized in the 2.3-kb cDNA. The expression of hGATA-3, a T cell-spe cific factor known to be involved in the regulation of the transcripti on of TcR delta locus, was analyzed by Northern blot, in cultured NK c ell population and clones (but not in freshly derived cell populations ). All NK clones and cell lines studied were found to express hGATA-3- specific mRNA, suggesting that hGATA-3 may be involved in the regulati on of the unrearranged TcR delta gene expression in NK cells. Finally, no transcription of the RAG-1 gene could be detected in all NK cell l ines or clones analyzed.