title: T cell homeostasis: thymus regeneration and peripheral T cell restoration in mice with a reduced fraction of competent precursors.
abstract: We developed a novel experimental strategy to study T cell regeneration after bone marrow transplantation. We assessed the fraction of competent precursors required to repopulate the thymus and quantified the relationship between the size of the different T cell compartments during T cell maturation in the thymus. The contribution of the thymus to the establishment and maintenance of the peripheral T cell pools was also quantified. We found that the degree of thymus restoration is determined by the availability of competent precursors and that the number of double-positive thymus cells is not under homeostatic control. In contrast, the sizes of the peripheral CD4 and CD8 T cell pools are largely independent of the number of precursors and of the number of thymus cells. Peripheral "homeostatic" proliferation and increased export and/or survival of recent thymus emigrants compensate for reduced T cell production in the thymus. In spite of these reparatory processes, mice with a reduced number of mature T cells in the thymus have an increased probability of peripheral T cell deficiency, mainly in the naive compartment.
authors.affiliation: Lymphocyte Population Biology, Unité de Recherche Associée Centre National de la Recherche Scientifique 1961, Institut Pasteur, 75015 Paris, France.
authors.forename: A R
authors.initials: AR
authors.lastname: Almeida
authors.forename: J A
authors.initials: JA
authors.lastname: Borghans
authors.forename: A A
authors.initials: AA
authors.lastname: Freitas
mesh_terms: D000818:Animals; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology; D004268:DNA-Binding Proteins / Q000172:deficiency / Q000235:genetics / Q000378:metabolism; D019673:Genes, T-Cell Receptor alpha; D018655:Lymphocyte Count; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D011948:Receptors, Antigen, T-Cell / Q000172:deficiency / Q000235:genetics / Q000276:immunology*; D012038:Regeneration; D013234:Stem Cells / Q000166:cytology / Q000276:immunology*; D013601:T-Lymphocytes / Q000276:immunology*; D013950:Thymus Gland / Q000166:cytology / Q000276:immunology / Q000502:physiology*; D019895:Transposases / Q000172:deficiency / Q000235:genetics / Q000378:metabolism
chemical_list: D004268:DNA-Binding Proteins; C499308:Rag2 protein, mouse; D011948:Receptors, Antigen, T-Cell; C064655:V(D)J recombination activating protein 2; D019895:Transposases