Evidence for expression of two distinct T cell receptor beta-chain transcripts in a human diphtheria toxoid-specific T cell clone.

We have cloned and sequenced the human T cell receptor alpha- and beta-chains cDNA present in a lambda gt10 library derived from a human CD4+ diphtheria toxoid-specific T cell clone, PH28. Two 1.3-kb beta-transcripts within frame V, D, J joining were found. These two functional beta-transcripts use two members of different V beta-families, V beta 3 and V beta 4, one joined to D beta 1-1, J beta 1-1, C beta 1, the other joined to D beta 1-1, J beta 2-1, C beta 2. Moreover, we have cloned the two different V beta germ-line counterparts whose sequences confirm that these two V beta are not pseudogenes. Analysis of T cell receptor beta and alpha rearrangements in PH28 showed that a single rearrangement on each chromosome could be assigned either at the J beta or the J gamma loci. These results strongly suggest an absence of allelic exclusion for 1.3-kb mRNA beta-transcripts in a human antigen-specific T cell clone.