EXPRESSION OF T-CELL RECEPTOR GENES IN THE THYMUS - LOCALIZATION OF TRANSCRIPTS INSITU AND COMPARISON OF MATURE AND IMMATURE SUBSETS

We have analyzed the expression of T cell receptor (TcR) genes in the thymus using in situ RNA hybridizations with probes to the constant regions of the TcR α, β, γ and δ chains. Localization of transcripts revealed low TcR α mRNA levels in the thymus cortex and very low levels in the subcapsular region. In contrast, TcR β message was very abundant in the cortex. TcR γ or δ mRNA+ thymocytes showed a scattered, predominantly cortical localization. In contrast to γ, TcR δ transcripts were abundant in the subcapsular region. Control experiments with sorted TcR α/β or γ/δ cells revealed a detection efficiency of 75%–85% for the respective TcR mRNA and data on TcR gene expression in mature, CD3+ thymocytes were consistent with previous reports. The analysis of immature, CD3− thymocyte subsets, however, revealed a virtual absence of TcR α transcripts and an unexpectedly high proportion of cells (14%–29%) expressing the gene for the TcR δ chain. The data are discussed in view of current models of lineage relationships in the thymus. Copyright © 1990 Wiley‐VCH Verlag GmbH & Co. KGaA