Specific deletion of the J-Cδ locus in murine α/β T cell clones and studies using transgenic mice

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Abstract
A deletion event in the T cell receptor (TcR) δ locus has been characterized in a panel of mouse α/β cytotoxic T lymphocyte (CTL) clones. Data presented here shows that Jδ1, Jδ2 and Cδ are absent from functional CTL clones while a germ‐line Dδ1 fragment is retained, thus suggesting a specific deletion of this region. We have investigated the possible significance of the J‐Cδ deletion by generating T cell lines from TcR α/β transgenic mice. Unlike control T cell lines which included a T cell line derived from a β transgenic mouse, the lines expressing the transgenic α/β heterodimer have not deleted the Cδ region. This strongly suggests that the J‐Cδ deletion event is not responsible for directing T cells to the α/β lineage, but rather is involved in the rearrangement or transcriptional activity of the α locus. In addition, to ensure that the α/β transgene does not have any inhibitory affects on the rearrangement of the δ loci in general, the γ/δ expressing dendritic epithelial Tcell (DETC) population was examined in TcR α/β transgenic mice and alterations in this T cell subset were not found. This finding that normal γ/δ DETC cells are present in α/β transgenic mice, together with the data showing that the Dδ1 region remains in an unrearranged germ‐line configuration in functional α/β CTL, suggests that commitment to the α/β or γ/δ lineage is predetermined at a particular stage in early T cell ontogeny.