Genes encoding the T-cell receptor alpha and beta subunits are transcribed in an ordered manner during intrathymic ontogeny.

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Abstract
To further characterize sequential events involved in activation of genes encoding the [human] T cell receptor (a complex of T3 molecules and a disulfide-linked heterodimer designated Ti, T3-Ti) for antigen and the major histocompatibility complex during intrathymic ontogeny, c[complementary]DNA probes specific for Ti .alpha. and Ti .beta. subunits were used for transcriptional analysis. Ti .beta. transcript levels were minimal in stage I thymocytes, maximal in stage II thymocytes, and intermediate in stage III thymocytes. Ti .alpha. transcriptional activity was virtually undetectable in stage I, was low in stage II, and achieved high levels only in the stage III compartment. Analysis of tumor populations derived from individual stages of thymic differentiation confirmed these observations and demonstrated that clonal stage I-II cells often express Ti .beta. RNA in the absence of Ti .alpha. RNA. The latter was not a consequence of functional Ti .alpha.-subunit isotypy because each of 13 interleukin 2-dependent T cell clones, including inducer, suppressor and cytotoxic T cells, contain transcripts that hybridize with the Ti .alpha. probe. Ti .beta. gene activation precedes Ti .alpha. gene activation. The high level of Ti .beta. mRNA preceding Ti .alpha. mRNA expression implies that Ti .beta. mRNA and/or its protein products may regulate Ti .alpha. gene transcription.