Visualization of the earliest steps of gammadelta T cell development in the adult thymus. Prinz, I., Sansoni, A., Kissenpfennig, A., Ardouin, L., Malissen, M., & Malissen, B. (2006). Visualization of the earliest steps of gammadelta T cell development in the adult thymus. Nature Immunology, 7(9)(9), 995-1003. https://doi.org/10.1038/ni1371 Published in: Nature Immunology Document Version: Early version, also known as pre-print Queen's University Belfast - Research Portal: Link to publication record in Queen's University Belfast Research Portal General rights Copyright for the publications made accessible via the Queen's University Belfast Research Portal is retained by the author(s) and / or other copyright owners and it is a condition of accessing these publications that users recognise and abide by the legal requirements associated with these rights. Take down policy The Research Portal is Queen's institutional repository that provides access to Queen's research output. Every effort has been made to ensure that content in the Research Portal does not infringe any person's rights, or applicable UK laws. If you discover content in the Research Portal that you believe breaches copyright or violates any law, please contact [email protected]. Download date:28. Sep. 2021 ARTICLES Visualization of the earliest steps of cd T cell development in the adult thymus Immo Prinz1, Amandine Sansoni1, Adrien Kissenpfennig1,2, Laurence Ardouin1, Marie Malissen1 & Bernard Malissen1 The checkpoint in cd cell development that controls successful T cell receptor (TCR) gene rearrangements remains poorly characterized. Using mice expressing a reporter gene ‘knocked into’ the Tcrd constant region gene, we have characterized many of the events that mark the life of early cd cells in the adult thymus. We identify the developmental stage during which the Tcrd locus ‘opens’ in early T cell progenitors and show that a single checkpoint controls cd cell development during the penultimate CD4–CD8– stage. Passage through this checkpoint required the assembly of cd TCR heterodimers on the cell surface and http://www.nature.com/natureimmunology signaling via the Lat adaptor protein. In addition, we show that cd selection triggered a phase of sustained proliferation similar to that induced by the pre-TCR. In mice, most T cells express T cell receptors (TCRs) consisting of self peptides bound to major histocompatibility complex molecules. a-andb-chains, whereas a minor population expresses an alternative This last developmental transition is known as positive selection. form made of g-andd-chains. Based on expression of CD25 and Knowledge of gd cell development remains limited3. Tcrb, Tcrg and CD44, the least mature double-negative (DN) CD4–CD8– thymocytes Tcrd rearrangements are postulated to occur simultaneously during can be organized according to the following maturation sequence: DN2 and DN3 stages, and most gd cells are DN and probably diverge CD44+CD25– (DN1) - CD44+CD25+ (DN2) - CD44neg–loCD25+ from ab T cell progenitors before the upregulation of CD4 and CD8 (DN3) - CD44–CD25– (DN4). DN4 cells give rise to double-positive expression. Mice lacking Tcrb (Tcrb–/– mice), which are incapable of Nature Publishing Group Group Nature Publishing 6 (DP) CD4+CD8+ thymocytes, a few of which develop further b-selection, have fewer DN3L cells. However, mice lacking both Tcrb + – – + 200 into single-positive CD4 CD8 or CD4 CD8 cells that migrate to and Tcrd have even fewer DN3L cells, suggesting that a small fraction © the periphery. of DN3L cells can be generated by expression of TCRd chains, and Genetic studies have defined two sequential checkpoints at which such d-selected cells probably give rise to mature TCRgd+ DN4 cells4. developing ab cells undergo programmed cell death if they fail to Consistent with that view, DN4 cells in Tcrb–/– mice are enriched in fulfill specific requirements1. Transition through the earliest check- productive Tcrd rearrangements, whereas these rearrangements are point requires assembly of the pre-TCR. This ‘molecular sensor’ random in DN3 cells4,5. ensures that only those DN3 cells containing productive Tcrb rear- Evidence suggests that in contrast to b-selection, d-selection does rangements develop into DN4 and DP thymocytes. Because Tcra not result in extensive proliferation of the selected cells4. Also at rearrangements occur after transition to the DP stage, the pre-TCR variance with the idea that gd cells encounter a developmental lacks a TCRa chain. It is composed of a pre-TCRa–TCRb heterodimer checkpoint at the DN3 stage is the observation that only 7–10% of and of CD3 signaling subunits. The phenotypic transition induced by DN4 cells contain intracellular TCRgd heterodimers6. Provided that the pre-TCR is referred to as ‘TCRb selection’ and is associated with such cells constitute the immediate precursors of mature DN4 gd cells, an intense phase of cell proliferation. The earliest b-selected thymo- those results, together with results published before7,suggestthatgd- cytes correspond to a minor subset of DN3 cells called ‘DN3L cells’ selection takes place at the DN4 stage and not at the DN3 stage. and are larger than their precursors, which are called ‘DN3E cells’. Therefore, the available data leave open the issue of whether the Preselection DN3E cells are noncycling and contain random Tcrb checkpoint thought to control gd cell development operates at the rearrangements, whereas b-selected DN3L cells are cycling and DN3 or DN4 stage. enriched in productive Tcrb rearrangements2. DP cells assemble a Because there is no phenotypic marker other than TCRgd itself for second molecular sensor consisting of a TCRa-TCRb heterodimer and tracking thymocytes committed to the gd lineage, delineation of gd of CD3 subunits. Successful differentiation into single-positive cells cell development has relied mainly on monitoring of the expression requires low-affinity interactions between TCRab heterodimers and of TCRgd heterodimers using antibodies that recognize epitopes 1Centre d’Immunologie de Marseille-Luminy, Universite´ de la Me´diterrane´e, Case 906, Institut National de la Sante´ et de la Recherche Me´dicale, U631, and Centre National de la Recherche Scientifique, UMR6102, 13288 Marseille, France. 2Present address: Infection and Immunity Group, Centre for Cancer Research and Cell Biology, School of Biomedical Sciences, Queen’s University, Belfast BT9 7AB, Northern Ireland. Correspondence should be addressed to B.M. ([email protected]). Received 30 May; accepted 6 July; published online 30 July 2006; doi:10.1038/ni1371 NATURE IMMUNOLOGY VOLUME 7 NUMBER 9 SEPTEMBER 2006 995 ARTICLES Figure 1 Characterization of Tcrd-H2BEGFP IEL TCRγδ+ NK1.1– TCRγδ+CD3+ ac4 mice. (a) Tcrd-H2BEGFP construct, containing 10 100 Tcrd-H2BEGFP an IRES-driven reporter cassette (I) encoding 103 80 an H2B (H)–EGFP (G) fusion protein in the IHG 60 3¢ untranslated region of Tcrd. To prevent any 102 C1 C2 C3 C4 24.1 40 γδ potential interference with rearrangement and % of max 101 expression of the targeted Tcrd allele, the ‘knock- 20 TCR in’ approach is limited to insertion of the IRES- b 100 0 100 101 102 103 104 100 101 102 103 104 driven cassette and of a residual loxPsite CD3 EGFP (triangle) in exon C4 of Tcrd. Filled boxes, exons d C1–C3. (b) Fluorescence microscopy of a small intestinal villus section stained with anti-B220 γδ (red) and DAPI (4¢,6-diamidino-2-phenylindole; γδ blue). Original magnification, 100. (c) Flow TCR TCR Â EGFP cytometry of IELs prepared from wild-type (gray EGFP B220 DAPI filled histogram) and Tcrd-H2BEGFP (black line) FSC CD3 EGFP small intestines and stained for CD3e,TCRab, TCRgd and NK1.1. EGFP fluorescence is analyzed in gated TCRgd+CD3e+ T cells, which represent 24.1% of TCRab–NK1.1– IELs. (d) Flow cytometry of marker expression on gated EGFPhi IELs. FSC, forward scatter. Data are representative of at least five independent experiments. generated by the association of TCRg and TCRd chains8,9.Ithas H2BEGFP expression in T cells and thymocytes therefore been impossible to identify gd T cell precursors before the Expression of the H2BEGFP reporter readily identified intraepithelial stage at which they express TCRgd heterodimers6.Herewehave lymphocytes (IELs) in the small intestine (Fig. 1b). All CD3e+TCRgd+ developed mice expressing a reporter gene ‘knocked into’ the Tcrd IELs from Tcrd-H2BEGFP mice were EGFPhi (Fig. 1c), whereas wild- constant region gene, thereby circumventing that technical limitation. type CD3e+TCRgd+ IELs were EGFPneg. Reciprocally, most EGFPhi http://www.nature.com/natureimmunology Using these mice, we have characterized gd T cell development IELs expressed TCRgd and CD3e at their surface (Fig. 1d). We noted from the point of opening of the Tcrd locus in a subset of early afewEGFPhi CD3e–TCRgd– IELs, which probably corresponded to T cell progenitors to the point of emergence of mature TCRgd+ activated IELs that had internalized their TCRgd-CD3 complexes. The DN4 thymocytes. distribution of amounts of CD3e and TCRgd on the surface of TCRgd+ IELs was rather broad, and CD3e and TCRgd surface amounts varied RESULTS in direct proportion to each other (Fig. 1c,d). This observation Generation of knock-in mice probably reflects the fact that each combination of g-andd-chains We introduced an expression cassette encoding an internal ribosomal has a distinct pairing efficiency and rate of export to the cell surface, entry site (IRES) and a fusion of human histone H2B and enhanced which influences the amount of TCRgd expressed on the surface of green fluorescence protein (EGFP)10 in the 3¢ untranslated region of each clone12. In contrast, the distribution of EGFP fluorescence in Nature Publishing Group Group Nature Publishing the Tcrd constant (C) gene (Fig. 1a and Supplementary Figs. 1 and 2 gd cells produced a sharp peak (Fig. 1d). We obtained similar results by 6 online). ‘Knock-in’ mice with the intended ‘Tcrd-H2BEGFP’mutation analysis of gd T cells in the spleen and lymph nodes (data not shown).