A novel human V_δ gene expressed predominantly in the TiγA fraction of γ/δ⁺ peripheral lymphocytes

We have characterized a functional T cell receptor (TcR) δ transcript in a TiγA⁺ human cloned cell line derived from peripheral blood. This cDNA includes a novel V gene (V‐AB12), whose expression was initially studied in a series of TcR γ/δ′ clones. Nine TiγA⁺ clones derived independently from distinct donors have been tested: each of them was found to possess a unique V‐AB12/J‐IDP2 5.5‐kb Eco RI rearrangement, which was constantly transcribed. Surface expression of the protein encoded by this unique rearranged gene was demonstrated by immunoprecipitations performed on three TiγA′ polyclonal cell lines using a specific rabbit heteroantiserum. Further analysis strongly suggested that a monoclonal antibody (mAb), designated anti‐BB3, detects a V‐ABl2‐encoded antigenic determinant on the cell surface. Double‐color immunofluorescence analysis of peripheral blood lymphocytes from ten donors indicated that most BB3⁺ cells are recognized by anti‐TiγA mAb. In previous studies, we have shown that a majority of TcR γ/δ⁺′ peripheral T cells expresses a γ chain including V9 (TiγA) and most frequently JP‐encoded peptides. Given the present results on the δ chain, it can be concluded that, in many individuals, a predominant fraction (V_γ9⁺/V‐AB12⁺) of circulating CD3⁺ TcRa/β⁻ T lymphocytes expresses a receptor with little, if any, combinatorial diversity.