title: Lymphopenia-driven homeostatic regulation of naive T cells in elderly and thymectomized young adults.
abstract: Reduced thymopoiesis and continuous mobilization of naive T cells into the effector-memory pool can lead to severe alterations of the naive T cell compartment. However, maintenance of the naive T cell population is essential to mount effective immune responses. Evidence of homeostatic regulation of naive T cells is currently debated in animal models. In humans, the situation remains unresolved, in particular with advanced age. In this study, we analyzed the CD4(+) and CD8(+) naive T cell compartments from elderly, young adults thymectomized during early childhood, and HIV-1-infected patients, which are characterized by T lymphocytopenia. We show a direct association between increased turnover and decreased frequency of naive T cells. Moreover, the IL-7-induced pathway was fully functional in naive T cells from elderly and young adults thymectomized during early childhood, who are characterized by elevated IL-7 plasma levels. Our findings support the establishment of homeostatic regulation of naive T cell proliferation in humans. This regulation is particularly active in lymphopenic hosts, such as elderly and thymectomized patients.
authors.affiliation: INSERM Unité Mixte de Recherche S 945, Infections and Immunity, Université Pierre et Marie Curie-Paris 6, Hôpital Pitié-Salpêtrière, 75013 Paris, France. delphine.sauce@upmc.fr
authors.forename: Delphine
authors.initials: D
authors.lastname: Sauce
authors.forename: Martin
authors.initials: M
authors.lastname: Larsen
authors.forename: Solène
authors.initials: S
authors.lastname: Fastenackels
authors.forename: Antoine
authors.initials: A
authors.lastname: Roux
authors.forename: Guy
authors.initials: G
authors.lastname: Gorochov
authors.forename: Christine
authors.initials: C
authors.lastname: Katlama
authors.forename: Daniel
authors.initials: D
authors.lastname: Sidi
authors.forename: Joyce
authors.initials: J
authors.lastname: Sibony-Prat
authors.forename: Victor
authors.initials: V
authors.lastname: Appay
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D002454:Cell Differentiation / Q000276:immunology*; D005260:Female; D006706:Homeostasis / Q000276:immunology*; D006801:Humans; D007156:Immunologic Memory / Q000276:immunology; D008231:Lymphopenia / Q000473:pathology*; D008297:Male; D008875:Middle Aged; D016176:T-Lymphocyte Subsets / Q000166:cytology* / Q000276:immunology* / Q000473:pathology; D013934:Thymectomy; D055815:Young Adult