title: Early T lymphocytes. Differentiation in vivo of adult intrathymic precursor cells.
abstract: A minor subpopulation of adult murine thymocytes (less than 5%) that is Lyt-2-, L3T4-, and expresses low levels of Ly-1 (designated dLy-1 [dull] thymocytes) has been identified, isolated, and characterized. This study assesses the differentiation potential of dLy-1 thymocytes in the thymus in vivo. Using multiparameter flow cytometry, radiation chimeras of C57BL/6 mice congenic at the Ly-1 or Ly-5 locus, and allelic markers to discriminate host and donor, we showed that transferred dLy-1 cells were able to generate thymocytes expressing both cortical and medullary phenotypes in a sequential manner. The proportion of donor-derived thymocytes obtained was directly related to the number of dLy-1 thymocytes transferred. Transfer of purified Lyt-2+ or Lyt-2+ + L3T4+ thymocytes, which constitute greater than 94% of total thymocytes, failed to generate any donor-derived thymocytes in irradiated recipients. Transfer of bone marrow (BM) cells produced the same sequential pattern of differentiation as that produced by dLy-1 cells, but was delayed by 4-5 d. Transferred dLy-1 thymocytes exhibited a limited capacity for self-renewal, and resulted in a single wave of differentiation in irradiated hosts. Thus, thymic repopulation by donor-derived cells after transfer of dLy-1 thymocytes was transient, while repopulation by BM was permanent. These findings suggest that the isolated dLy-1 thymocytes described herein are precursor thymocytes that represent a very early stage in intrathymic development.
authors.forename: B J
authors.initials: BJ
authors.lastname: Fowlkes
authors.forename: L
authors.initials: L
authors.lastname: Edison
authors.forename: B J
authors.initials: BJ
authors.lastname: Mathieson
authors.forename: T M
authors.initials: TM
authors.lastname: Chused
mesh_terms: D000818:Animals; D000950:Antigens, Ly / Q000032:analysis; D016026:Bone Marrow Transplantation; D002454:Cell Differentiation; D005260:Female; D018380:Hematopoietic Stem Cell Transplantation; D006412:Hematopoietic Stem Cells / Q000166:cytology; D006801:Humans; D051379:Mice; D008809:Mice, Inbred C3H; D008810:Mice, Inbred C57BL; D011828:Radiation Chimera; D013601:T-Lymphocytes / Q000145:classification / Q000166:cytology* / Q000276:immunology
chemical_list: D000950:Antigens, Ly