{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,4,11]],"date-time":"2026-04-11T12:40:56Z","timestamp":1775911256738,"version":"3.50.1"},"reference-count":36,"publisher":"Proceedings of the National Academy of Sciences","issue":"5","content-domain":{"domain":["www.pnas.org"],"crossmark-restriction":true},"short-container-title":["Proc. Natl. Acad. Sci. U.S.A."],"published-print":{"date-parts":[[2009,2,3]]},"abstract":"<jats:p>The thymus represents the \u201ccradle\u201d for T cell development, with thymic stroma providing multiple soluble and membrane cues to developing thymocytes. Although IL-7 is recognized as an essential factor for thymopoiesis, the \u201cenvironmental niche\u201d of thymic IL-7 activity remains poorly characterized in vivo. Using bacterial artificial chromosome transgenic mice in which YFP is under control of IL-7 promoter, we identify a subset of thymic epithelial cells (TECs) that co-express YFP and high levels of<jats:italic>Il7<\/jats:italic>transcripts (IL-7<jats:sup>hi<\/jats:sup>cells). IL-7<jats:sup>hi<\/jats:sup>TECs arise during early fetal development, persist throughout life, and co-express homeostatic chemokines (<jats:italic>Ccl19<\/jats:italic>,<jats:italic>Ccl25<\/jats:italic>,<jats:italic>Cxcl12<\/jats:italic>) and cytokines (<jats:italic>Il15<\/jats:italic>) that are critical for normal thymopoiesis. In the adult thymus, IL-7<jats:sup>hi<\/jats:sup>cells localize to the cortico-medullary junction and display traits of both cortical and medullary TECs. Interestingly, the frequency of IL-7<jats:sup>hi<\/jats:sup>cells decreases with age, suggesting a mechanism for the age-related thymic involution that is associated with declining IL-7 levels. Our temporal-spatial analysis of IL-7-producing cells in the thymus in vivo suggests that thymic IL-7 levels are dynamically regulated under distinct physiological conditions. This IL-7 reporter mouse provides a valuable tool to further dissect the mechanisms that govern thymic IL-7 expression in vivo.<\/jats:p>","DOI":"10.1073\/pnas.0809559106","type":"journal-article","created":{"date-parts":[[2009,1,22]],"date-time":"2009-01-22T02:40:22Z","timestamp":1232592022000},"page":"1512-1517","update-policy":"https:\/\/doi.org\/10.1073\/pnas.cm10313","source":"Crossref","is-referenced-by-count":131,"title":["Characterization of the thymic IL-7 niche in vivo"],"prefix":"10.1073","volume":"106","author":[{"given":"Nuno L.","family":"Alves","sequence":"first","affiliation":[{"name":"Cytokines and Lymphoid Development Unit,"},{"name":"INSERM U668, Paris, France; and"}]},{"given":"Odile Richard-Le","family":"Goff","sequence":"additional","affiliation":[{"name":"Cytokines and Lymphoid Development Unit,"},{"name":"INSERM U668, Paris, France; and"}]},{"given":"Nicholas D.","family":"Huntington","sequence":"additional","affiliation":[{"name":"Cytokines and Lymphoid Development Unit,"},{"name":"INSERM U668, Paris, France; and"}]},{"given":"Ana Patricia","family":"Sousa","sequence":"additional","affiliation":[{"name":"Lymphocyte Development Unit,"},{"name":"INSERM U668, Paris, France; and"}]},{"given":"Vera S. G.","family":"Ribeiro","sequence":"additional","affiliation":[{"name":"Cytokines and Lymphoid Development Unit,"},{"name":"INSERM U668, Paris, France; and"}]},{"given":"Allison","family":"Bordack","sequence":"additional","affiliation":[{"name":"Cytokines and Lymphoid Development Unit,"},{"name":"INSERM U668, Paris, France; and"}]},{"given":"Francina Langa","family":"Vives","sequence":"additional","affiliation":[{"name":"Plate-Forme Technologique Centre d'Ing\u00e9nierie G\u00e9n\u00e9tique Murine, and"}]},{"given":"Lucie","family":"Peduto","sequence":"additional","affiliation":[{"name":"Laboratory of Lymphoid Tissue Development, Institut Pasteur, Paris, France;"}]},{"given":"Ann","family":"Chidgey","sequence":"additional","affiliation":[{"name":"Monash Immunology and Stem Cell Laboratories (MISCL), Monash University, Victoria 3800, Australia"}]},{"given":"Ana","family":"Cumano","sequence":"additional","affiliation":[{"name":"Lymphocyte Development Unit,"},{"name":"INSERM U668, Paris, France; and"}]},{"given":"Richard","family":"Boyd","sequence":"additional","affiliation":[{"name":"Monash Immunology and Stem Cell Laboratories (MISCL), Monash University, Victoria 3800, Australia"}]},{"given":"Gerard","family":"Eberl","sequence":"additional","affiliation":[{"name":"Laboratory of Lymphoid Tissue Development, Institut Pasteur, Paris, France;"}]},{"given":"James P.","family":"Di Santo","sequence":"additional","affiliation":[{"name":"Cytokines and Lymphoid Development Unit,"},{"name":"INSERM U668, Paris, France; and"}]}],"member":"341","published-online":{"date-parts":[[2009,2,3]]},"reference":[{"key":"e_1_3_3_1_2","doi-asserted-by":"publisher","DOI":"10.1146\/annurev.iy.13.040195.000521"},{"key":"e_1_3_3_2_2","doi-asserted-by":"publisher","DOI":"10.1146\/annurev.immunol.23.021704.115601"},{"key":"e_1_3_3_3_2","doi-asserted-by":"publisher","DOI":"10.1146\/annurev.immunol.14.1.73"},{"key":"e_1_3_3_4_2","doi-asserted-by":"publisher","DOI":"10.1038\/ni723"},{"key":"e_1_3_3_5_2","doi-asserted-by":"publisher","DOI":"10.1146\/annurev.immunol.23.021704.115715"},{"key":"e_1_3_3_6_2","doi-asserted-by":"publisher","DOI":"10.1073\/pnas.92.2.377"},{"key":"e_1_3_3_7_2","doi-asserted-by":"publisher","DOI":"10.1084\/jem.181.4.1519"},{"key":"e_1_3_3_8_2","doi-asserted-by":"publisher","DOI":"10.1084\/jem.180.5.1955"},{"key":"e_1_3_3_9_2","doi-asserted-by":"publisher","DOI":"10.1182\/blood.V99.11.3892"},{"key":"e_1_3_3_10_2","doi-asserted-by":"publisher","DOI":"10.1038\/ni1513"},{"key":"e_1_3_3_11_2","doi-asserted-by":"publisher","DOI":"10.4049\/jimmunol.178.8.4956"},{"key":"e_1_3_3_12_2","doi-asserted-by":"publisher","DOI":"10.4049\/jimmunol.174.1.60"},{"key":"e_1_3_3_13_2","doi-asserted-by":"publisher","DOI":"10.1038\/83381"},{"key":"e_1_3_3_14_2","doi-asserted-by":"publisher","DOI":"10.1016\/j.mad.2006.01.016"},{"key":"e_1_3_3_15_2","doi-asserted-by":"publisher","DOI":"10.1016\/j.smim.2007.10.006"},{"key":"e_1_3_3_16_2","doi-asserted-by":"publisher","DOI":"10.1002\/gene.10249"},{"key":"e_1_3_3_17_2","doi-asserted-by":"crossref","first-page":"1026","DOI":"10.4049\/jimmunol.138.4.1026","article-title":"Cell kinetics in the fetal mouse thymus: precursor cell input, proliferation, and emigration","volume":"138","author":"Jotereau F","year":"1987","unstructured":"F Jotereau, F Heuze, V Salomon-Vie, H Gascan, Cell kinetics in the fetal mouse thymus: precursor cell input, proliferation, and emigration. 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