Regulation of T-cell receptor gene expression in human T-cell development.

A cDNA clone encoding the alpha chain of the human T-cell antigen receptor was isolated by screening a library from the human T-cell line Jurkat with a mouse alpha-chain cDNA clone. This human alpha-chain clone, together with a human antigen receptor beta-chain cDNA clone, was used to determine the stage of T-cell development at which antigen receptor mRNAs first appear. Blot-hybridization analysis of mRNA isolated from a panel of human thymic tumor lines clearly demonstrated that beta-chain transcripts could be detected in all T-lineage cells. However, alpha-chain transcripts were only found in the most phenotypically mature lines, which express the antigen receptor-associated molecule T3. Furthermore, beta-chain transcripts were abundant in RNA prepared from purified T3-negative thymocytes, whereas alpha-chain transcripts were virtually absent. From these results we conclude that alpha-chain expression occurs later in thymic ontogeny than that of the beta chain and propose that it controls surface expression of the antigen receptor-T3 complex.