title: Human recent thymic emigrants--identification, expansion, and survival characteristics.
abstract: This study shows that, in humans at birth, circulating T cells represent recent thymic emigrants (RTEs) as reflected in their high level of expression of TCR excision circles. RTEs express "thymocyte-like" characteristics with regard to rapid rate of apoptosis. In the presence of common gamma-chain cytokines, in particular IL-7, they show enhanced potential to survive, entry into cell cycle, and proliferation. Although common gamma-chain cytokines were also potent antiapoptotic stimuli for mature adult-derived naive CD4+CD45RA+ T cells, these cells were refractory to IL-7-induced expansion in vitro. RTEs cultured with IL-7 could not reinduce recombination-activating gene-2 gene expression in vitro. These data suggest that postthymic naive T cells in the periphery during early life are at a unique stage in ontogeny as RTEs, during which they can undergo homeostatic regulation including expansion and survival in an Ag-independent manner while maintaining their preselected TCR repertoire.
authors.affiliation: Children's Research Centre, Our Lady's Hospital for Sick Children, Dublin, Ireland. jaythoon.hassan@ucd.ie
authors.forename: J
authors.initials: J
authors.lastname: Hassan
authors.forename: D J
authors.initials: DJ
authors.lastname: Reen
mesh_terms: D000328:Adult; D017209:Apoptosis / Q000276:immunology; D002455:Cell Division / Q000276:immunology; D002465:Cell Movement / Q000276:immunology*; D002470:Cell Survival / Q000276:immunology; D002478:Cells, Cultured; D016207:Cytokines / Q000502:physiology; D004254:DNA Nucleotidyltransferases / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism; D005312:Fetal Blood / Q000166:cytology / Q000276:immunology / Q000378:metabolism; D018398:Homeodomain Proteins / Q000378:metabolism; D006706:Homeostasis / Q000276:immunology; D006801:Humans; D016130:Immunophenotyping; D019426:Integrases; D007399:Interphase / Q000276:immunology; D007700:Kinetics; D008213:Lymphocyte Activation / Q000276:immunology; D009687:Nuclear Proteins; D011948:Receptors, Antigen, T-Cell / Q000096:biosynthesis; D045522:Recombinases; D016176:T-Lymphocyte Subsets / Q000166:cytology* / Q000201:enzymology / Q000378:metabolism; D013950:Thymus Gland / Q000166:cytology* / Q000201:enzymology / Q000378:metabolism
chemical_list: D016207:Cytokines; D004268:DNA-Binding Proteins; D018398:Homeodomain Proteins; D009687:Nuclear Proteins; C499311:RAG2 protein, human; D011948:Receptors, Antigen, T-Cell; D045522:Recombinases; C064655:V(D)J recombination activating protein 2; C064658:RAG-1 protein; D004254:DNA Nucleotidyltransferases; D019426:Integrases; C115006:integron integrase IntI1