title: Auto-reconstitution of the T-cell compartment by radioresistant hematopoietic cells following lethal irradiation and bone marrow transplantation.
abstract: OBJECTIVE
  In lethally irradiated bone marrow chimeras, part of the reconstituted T-cell compartment is derived from the irradiated host, but the detailed origin and functional activity of host-derived T cells has not been thoroughly analyzed. Herein, we determine the origin and function of radioresistant host-derived T cells.
  
  
  METHODS
  Lethally irradiated thymectomized or nonthymectomized C57BL/6 host mice were reconstituted with syngeneic bone marrow, itself incapable of generating T cells. Using fetal thymic organ cultures, bulk and limiting dilution assays on OP9-DL1 stromal cells, unambiguous cohorts of thymus-derived and peripheral T-cell-derived T cells were phenotypically characterized by flow cytometry and functionally characterized by their ability to participate in a T-cell-dependent antibody response.
  
  
  RESULTS
  Both thymus-derived and peripheral T-cell-derived host T cells are functional and can reconstitute 35% of the normal T-cell pool. By comparing thymectomized vs nonthymectomized hosts, host-derived T cells were shown to comprise a major (70%) subpopulation of de novo generated, thymus-derived, polyclonal, naïve cells, and a minor subpopulation of surviving, peripheral, oligoclonal, memory-like cells. Unlike euthymic recipients, mice whose T cells were derived from surviving peripheral T cells were frequently incapable of mounting a T-cell-dependent antibody response. Host-derived thymocytes regenerated in an interleukin-7-dependent fashion from conventional DN2 thymocytes and their differentiation recapitulated normal thymic ontogeny.
  
  
  CONCLUSIONS
  We characterized, for the first time, functional radioresistant DN2-phenotype thymic T-cell precursors, the T-cell progeny of which might provide a first line of defense against infections during the lymphopenic phase post-bone marrow transplantation.
authors.affiliation: Department of Biomedicine, Group of Developmental and Molecular Immunology, University of Basel, Basel, Switzerland.
authors.forename: Nabil
authors.initials: N
authors.lastname: Bosco
authors.forename: Lee Kim
authors.initials: LK
authors.lastname: Swee
authors.forename: Angèle
authors.initials: A
authors.lastname: Bénard
authors.forename: Rhodri
authors.initials: R
authors.lastname: Ceredig
authors.forename: Antonius
authors.initials: A
authors.lastname: Rolink
mesh_terms: D000818:Animals; D016026:Bone Marrow Transplantation; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology / Q000378:metabolism; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology / Q000378:metabolism; D005260:Female; D005434:Flow Cytometry; D006183:H-2 Antigens / Q000235:genetics / Q000378:metabolism; D006412:Hematopoietic Stem Cells / Q000276:immunology* / Q000378:metabolism / Q000528:radiation effects; D016130:Immunophenotyping; D017493:Leukocyte Common Antigens / Q000235:genetics / Q000378:metabolism; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008822:Mice, Transgenic; D011247:Pregnancy; D013154:Spleen / Q000166:cytology / Q000276:immunology; D013601:T-Lymphocytes / Q000276:immunology* / Q000378:metabolism; D013934:Thymectomy; D013950:Thymus Gland / Q000166:cytology / Q000196:embryology / Q000276:immunology*; D018183:Transplantation Chimera / Q000276:immunology
chemical_list: D006183:H-2 Antigens; C032876:H-2Kb protein, mouse; D017493:Leukocyte Common Antigens; C516770:Ptprc protein, mouse