Rearrangement and Expression of T-Cell Antigen Receptor Genes in Human T-Lymphocyte Tumor Lines and Normal Human T-Cell Clones: Evidence for Allelic Exclusion of Tiβ Gene Expression and Preferential Use of a Jβ2 Gene Segment

The gene encoding the β chain of the human T-cell receptor for antigen is composed of variable (V), diversity (D), joining (J), and constant (C) gene segments which undergo specific rearrangements during T-lymphocyte ontogeny. Southern blot analyses of seven human T-cell tumor lines and normal human T-lymphocyte clones revealed that most of these T-cell lines rearrange their Tiβ genes differently. The T-cell tumor line HPB-MLT rearranges and transcribes both of its Tiβ genes. Cloning and sequencing of the Tiβ cDNAs corresponding to these rearrangements revealed that one of the rearranged Tiβ genes is defective, while the other is functional and corresponds to the Tiβ protein expressed on the surface of these cells. Thus, this cell line displays a pattern of allelic exclusion of Tiβ gene expression. A comparison of four Cβ2-containing Tiβ cDNAs from three different cell lines revealed that three of the four utilize the same Jβ2.5 gene segment joined to different Dβ and Vβ genes, suggesting that there may be preferential use of this J gene during Jβ2 rearrangements. Hybridization analyses with probes for the α and β genes of the T-cell receptor and the T-cell-specific Tγ gene revealed that HPB-MLT cells appear to express approximately equivalent amounts of RNA corresponding to each of the rearranged Tiα and Tiβ genes. However, they express a much lower level of Tγ RNA.