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Different expression of the recombination activity gene RAG‐1 in various populations of thymocytes, peripheral T cells and gut thymus‐independent intraepithelial lymphocytes suggests two pathways of T cell receptor rearrangement

1992; Wiley; Volume: 22; Issue: 2 Linguagem: Inglês

10.1002/eji.1830220232

1521-4141

Delphine Guy‐Grand, C. Vanden Broecke, C Briottet, Michèle Malassis-Séris, Françoise Selz, P Vassalli,

Hematopoietic Stem Cell Transplantation

Abstract The presence of transcripts of the recombination activating gene RAG‐1 was studied by in situ hybridization on selected populations of murine thymocytes, peripheral lymphocytes and gut intraepithelial lymphocytes (IEL), obtained by cell sorting. RAG‐1 mRNA was found in a majority of “double‐positive” (DP) thymocytes, but was absent in “single‐positive” thymocytes and peripheral T lymphocytes. The only other T lineages in which about 10%–20% of the cells contained RAG‐1 mRNA, and in smaller amounts, were “double‐negative” (DN), T cell receptor (TcR) γ δ ‐ cortical thymocytes and gut CD3 − IEL. These observations suggest that (a) the high expression of RAG‐1 transcripts in DP thymocytes is related to the process of expansion‐selection of these cells, probably accompanied by repeated TcR rearrangements, and that (b) in contrast. CD3 − IEL from the gut (which are thymus independent) as well as some DN thymocytes undergo limited TcR rearrangement giving rise locally to TcR + T cells without prior extensive process of local expansion‐selection. A small percentage of peripheral B cells also contained RAG‐1 mRNA, raising the possibility that this protein may also be involved in immunoglobulin class switching.