Rearrangement and diversity of T cell receptor beta chain genes in thymocytes: a critical role for the beta chain in development.

Thymocytes from mice congenitally deficient for TCR alpha chain synthesis were examined for the status of their TCR beta chain genes, by DNA sequencing and by a novel technique that analyzes populations of gene rearrangements. TCR beta chain genes were predominantly productively rearranged, in contrast with the statistical prediction for a quasi-random rearrangement process. Therefore, productive TCR beta chain gene rearrangement appears to be a critical step in thymocyte maturation, independent of TCR alpha chain expression. Moreover, the beta chain gene rearrangements in TCR alpha-/-mice are typical of those found in the thymus and periphery of normal mice. Thus, the extent of junctional diversity is a property of TCR genes that is imposed prior to selection on the mature alpha beta TCR.