Analysis of early fetal T-cell receptor δ chain in humans

In the mouse it has been found that a number of T-cell receptor (Tcr) gd phenotypes are generated during fetal thymic development. To examine whether such "waves" of Tcrgd phenotypes can be found in man, we studied the V-region usage and junctional diversity of the T-cell receptor δ chain in human fetal and post-partum thymocytes and peripheral blood T cells. Using the polymerase chain reaction (PCR)-amplification technique it was found that in fetal thymocytes of 15-17 weeks of gestation the Tcrd-V3 gene segment was mainly employed, whereas in post-partum thymocytes the Tcrd-V1 gene segment was preferentially used. These Tcrd-V3 transcripts contained only a single D element (Dδ3) and a limited random nucleotide insertion. The Dδ3 element was also present in Tcrd-V3-containing transcripts derived from peripheral blood γδ Tcr⁺ clones. These data suggest that a wave of Tcr γδ might exist early in human fetal development that preferentially use the Tcrd-V3 gene segment.