T cell receptor gene trans-rearrangements: chimeric gamma-delta genes in normal lymphoid tissues.

Joining of V-, D-, and J-region gene segments during DNA rearrangements within all antigen receptor genes involves recognition of the same highly conserved heptamernonamer sequences flanking each segment. In order to investigate the possibility that recognition of these conserved sequences may sometimes permit intergenic joining of segments among different antigen receptor genes, DNA of normal human lymphoid tissues was examined by polymerase chain reaction amplification for the presence of chimeric gamma-delta T cell receptor gene rearrangements. These studies detected V gamma-(D delta)-J delta and V delta-(D delta)-J gamma rearrangements in thymus, peripheral blood, and tonsil. Analysis of thymus RNA indicated that many of these rearrangements are expressed as V gamma-(D delta)-J delta-C delta and V delta-(D delta)-J gamma-C gamma transcripts. Most transcripts (19 of 20 complementary DNA clones studied) are appropriately spliced and show correct open translational reading frames across the V-(D)-J junctions. Thus, chimeric antigen receptor genes are generated in a subset of normal lymphoid cells, probably as a result of chromosomal translocations, and such genes may possibly contribute to increased diversity within the antigen receptor repertoire.