title: Lymphocyte development from stem cells.
abstract: Highly enriched pluripotent and multipotent hematopoietic stem cells (HSCs) are isolated from bone marrow and fetal liver as Thy-1loLin-Sca-1+ cells. Pluripotent HSCs express c-kit receptor on their surface, but the generation and proliferation of early fetal HSCs take place in the absence of steel factor. T precursor cells migrate into the fetal thymus by chemotactic mechanism. CD4lo precursors represent a newly defined phase of T-cell development in the thymus between the bone marrow-derived stem cells and the CD4-8- intrathymic precursors. Only fetal, but not adult, HSCs have the capacity to differentiate into V gamma 3+ and V gamma 4+ T cells under the fetal thymic microenvironment, and HSC themselves may lose some of their developmental potential during ontogeny. It is postulated that HSCs are the locus of a complicated but precise developmental clock that may determine both the time-dependent closure of some gene loci (e.g. V gamma 3 and V gamma 4 T cell receptor, and embryonic and fetal globin) and the activation of others (e.g. the N nucleotide insertion machinery).
authors.affiliation: Howard Hughes Medical Institute, Standord University School of Medicine, California 94305.
authors.forename: K
authors.initials: K
authors.lastname: Ikuta
authors.forename: N
authors.initials: N
authors.lastname: Uchida
authors.forename: J
authors.initials: J
authors.lastname: Friedman
authors.forename: I L
authors.initials: IL
authors.lastname: Weissman
mesh_terms: D000818:Animals; D006410:Hematopoiesis / Q000235:genetics / Q000276:immunology; D016298:Hematopoietic Cell Growth Factors / Q000276:immunology; D006412:Hematopoietic Stem Cells / Q000166:cytology / Q000276:immunology; D008214:Lymphocytes / Q000166:cytology* / Q000276:immunology; D051379:Mice; D011518:Proto-Oncogene Proteins / Q000276:immunology; D019009:Proto-Oncogene Proteins c-kit; D019089:Stem Cell Factor
chemical_list: D016298:Hematopoietic Cell Growth Factors; D011518:Proto-Oncogene Proteins; D019089:Stem Cell Factor; D019009:Proto-Oncogene Proteins c-kit