Expression of a wide T cell receptor Vβ repertoire in human T lymphocytes derived in vitro from embryonic liver cell precursors *

As shown recently, CD3⁺/TcR⁺ functional T lymphocytes can be derived in culture from embryonic liver cell precursors at a gestational age (6-8 weeks) preceeding the colonization of the epithelial thymus. In this report, we analyzed the Vβ repertoire of T lymphocytes derived from embryonic liver by applying a quantitative reverse transcriptase-polymerase chain reaction technique. To this end, oligonucleotide primers for Cα or the various human Vβ have been used to study both freshly derived embryonic liver cell suspensions and CD3⁺/TcR⁺ populations derived after approximately 6 weeks upon stimulation with 1% phytohemagglutinin and culture in 100 units/ml recombinant interleukin-2. In order to exclude possible contaminations with mother-derived T lymphocytes, only T cells displaying both X and Y chromosomal sequences (i.e. derived from male embryos) were further analyzed. While neither Cα nor the various Vβ could be detected in fresh liver cells, Cα and the large majority of Vβ were detected in in vitro cultured populations. The levels of the various Vβ expressed by embryo-derived T cells was similar to that detected in adult peripheral blood-derived T lymphocytes. These experiments indicate that the immature liver precursors can potentially give rise in vitro to T cells which express a wide Vβ repertoire and may provide a suitable in vitro system for the analysis of the selection processes mediated by either major histocompatibility complex antigen or superantigens.