title: Recent thymic emigrants are preferentially incorporated only into the depleted T-cell pool.
abstract: Recent thymic emigrants (RTEs) are the youngest subset of peripheral T cells, and they differ functionally and phenotypically from the rest of the naïve T-cell pool. RTEs are present in the peripheral T-cell pool throughout life but are the most common subset of T cells in neonates and adults recovering from lymphoablation. Using a murine model to study the homeostasis of RTEs, we show that under lymphoreplete conditions, RTEs are at a competitive disadvantage to already established mature naïve (MN) T cells. This disadvantage may be caused by a defect in survival, because RTEs may transduce homeostatic signals inefficiently, and their ability to survive is enhanced with increased expression of IL-7 receptor or B-cell lymphoma 2 (Bcl-2). Conversely, under lymphopenic conditions, enhanced proliferation by RTEs allows them to out-compete their MN T-cell counterparts. These results suggest that in times of need, such as in neonates or lymphopenic adults, RTEs perform well to fill the gaps in the peripheral T-cell pool, but when the periphery already is full, many RTEs are not incorporated into the pool of recirculating lymphocytes.
authors.affiliation: Department of Immunology, University of Washington, Seattle, WA 98195, USA.
authors.forename: Evan G
authors.initials: EG
authors.lastname: Houston
authors.forename: Lauren E
authors.initials: LE
authors.lastname: Higdon
authors.forename: Pamela J
authors.initials: PJ
authors.lastname: Fink
mesh_terms: D000818:Animals; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D006801:Humans; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D020395:Receptors, Interleukin-7 / Q000276:immunology; D016176:T-Lymphocyte Subsets / Q000166:cytology / Q000276:immunology; D013601:T-Lymphocytes / Q000166:cytology* / Q000276:immunology*; D013950:Thymus Gland / Q000166:cytology* / Q000276:immunology*
chemical_list: D004268:DNA-Binding Proteins; C499308:Rag2 protein, mouse; D020395:Receptors, Interleukin-7