Diversity and Structure of Human T-Cell Receptor α -Chain Variable Region Genes

The nucleotide sequences of 27 T-cell receptor α -chain variable region (Vα)-containing cDNA clones isolated from a cDNA library derived from human peripheral blood lymphocytes were determined. Eighteen different Vα and 26 different joining (Jα) gene segments are utilized in these clones. The Vα gene segments belong to 12 different subfamilies, each containing from one to seven members. Comparisons with the 16 different Vα and 21 different Jα sequences previously reported suggest that the germ-line repertoires for these gene segments are greater than previously estimated. Flexibility in the sites of gene segment joining and possibly N-region diversification also contribute to human α -chain diversity. Comparisons of human Vα regions indicate a high degree of variability spread uniformly across the entire Vα region without obvious hypervariable regions. However, amino acids important for the maintenance of V gene structure are conserved.