Separate lineages of T cells expressing the alpha beta and gamma delta receptors.
The T-cell antigen receptor is a heterodimer molecule composed of either alpha beta or gamma delta chains. The alpha beta receptor molecules are expressed mainly in CD4+ CD8- and CD4- CD8+ T cells (helper and killer T cells respectively), whereas the gamma delta receptor molecules are expressed mainly in CD4- CD8- T cells. CD4+CD8- and CD4-CD8+ T cells arise from a class of CD4-CD8- T cells during thymus development, raising the question of whether cells rearranging their gamma delta receptors later give rise to alpha beta T cells by further rearrangements of their receptor genes, or whether rearrangements and expression of the receptor genes occur in separate lineages. The delta-chain gene is located between the V alpha (variable) and J alpha (joining) gene segments, and when the rearrangements allowing alpha- and beta-receptors occur, the DNA between these segments is deleted as small circles which can be isolated from developing thymocytes. The rearrangement status of the delta-chain gene in the alpha-circles can therefore be investigated to see whether alpha-chain and delta-chain expression occur in parallel lineages or sequentially within a lineage. We find that the delta-chain gene in the T-cell receptor alpha-circles has a germline configuration, indicating that alpha beta and gamma delta T cells are distinct lineages.
Winoto
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Whitehead Institute for Biomedical Research, Cambridge Massachusetts 02142.
Baltimore
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D000818:Animals; D002454:Cell Differentiation; D015342:DNA Probes; D015329:Gene Rearrangement, T-Lymphocyte; D051379:Mice; D008806:Mice, Inbred AKR; D011948:Receptors, Antigen, T-Cell / Q000235:genetics*
D015342:DNA Probes; D011948:Receptors, Antigen, T-Cell