title: Requirement for the thymus in alphabeta T lymphocyte lineage commitment.
abstract: We recently identified a fetal thymic developmental stage (NK1.1+/CD117(lo)) that characterizes committed T/NK progenitors. We now report the existence of phenotypically and functionally identical T/NK progenitors in mouse fetal blood and spleen but not in fetal liver. These precursors are indistinguishable from previously characterized fetal blood "prothymocytes" (CD90+/CD117(lo)), with the exception that they express NK1.1, lack markers associated with T lineage commitment, maintain a germline TCRbeta locus, and can give rise to both T and NK cells. Moreover, NK1.1+/CD90+/CD117(lo) fetal blood precursors are present in athymic nude mice. These results suggest that the T/NK lineage commitment pathway is thymus-independent. In contrast, full commitment to the alphabeta T lineage does not precede thymus colonization.
authors.affiliation: Department of Immunology, University of Toronto, Ontario, Canada.
authors.forename: J R
authors.initials: JR
authors.lastname: Carlyle
authors.forename: J C
authors.initials: JC
authors.lastname: Zúñiga-Pflücker
mesh_terms: D000818:Animals; D001402:B-Lymphocytes / Q000166:cytology; D001854:Bone Marrow Cells / Q000166:cytology; D002454:Cell Differentiation; D019070:Cell Lineage / Q000235:genetics / Q000276:immunology; D018920:Coculture Techniques; D005260:Female; D005312:Fetal Blood / Q000166:cytology; D015870:Gene Expression; D007694:Killer Cells, Natural / Q000166:cytology / Q000502:physiology; D051379:Mice; D008819:Mice, Nude; D009924:Organ Culture Techniques; D016133:Polymerase Chain Reaction; D016693:Receptors, Antigen, T-Cell, alpha-beta / Q000235:genetics / Q000276:immunology*; D013154:Spleen / Q000166:cytology / Q000502:physiology; D017154:Stromal Cells / Q000166:cytology; D013601:T-Lymphocytes / Q000166:cytology* / Q000276:immunology*; D013950:Thymus Gland / Q000166:cytology / Q000502:physiology*
chemical_list: D016693:Receptors, Antigen, T-Cell, alpha-beta