Retraction. In individual T cells one productive alpha rearrangement does not appear to block rearrangement at the second allele.

The T cell lymphoma line BW5147 has rearranged TCR alpha chain genes segments on both the homologous chromosomes: one is functional (V alpha 1) and the second (V alpha 16.1) is a pseudogene. The extreme 3' position of the V alpha 16.1 gene segment in the V alpha locus allows us to recognize rearrangements of most V alpha gene segments using the V alpha 16 probe as a marker. The absence of the genomic V alpha 16.1 gene fragment in mature thymocytes, antigen-specific T cells, and in more than two-thirds of the peripheral T cells suggests that most T lymphocytes rearrange both alpha loci. It appears that productive alpha chain rearrangement on one allele probably does not block a subsequent rearrangement on the other alpha locus.