Diversity and structure of human T-cell receptor alpha-chain variable region genes

The nucleotide sequences of 27 T-cell receptor alpha-chain variable region (V alpha)-containing cDNA clones isolated from a cDNA library derived from human peripheral blood lymphocytes were determined. Eighteen different V alpha and 26 different joining (J alpha) gene segments are utilized in these clones. The V alpha gene segments belong to 12 different subfamilies, each containing from one to seven members. Comparisons with the 16 different V alpha and 21 different J alpha 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 alpha-chain diversity. Comparisons of human V alpha regions indicate a high degree of variability spread uniformly across the entire V alpha region without obvious hypervariable regions. However, amino acids important for the maintenance of V gene structure are conserved.