title: NK1.1+ T cells in the liver arise in the thymus and are selected by interactions with class I molecules on CD4+CD8+ cells.
abstract: NK1.1+ T cells represent a specialized T cell subset specific for CD1d, a nonclassical MHC class I-restricting element. They are believed to function as regulatory T cells. NK1.1+ T cell development depends on interactions with CD1d molecules presented by hematopoietic cells rather than thymic epithelial cells. NK1.1+ T cells are found in the thymus as well as in peripheral organs such as the liver, spleen, and bone marrow. The site of development of peripheral NK1.1+ T cells is controversial, as is the nature of the CD1d-expressing cell that selects them. With the use of nude mice, thymectomized mice reconstituted with fetal liver cells, and thymus-grafted mice, we provide direct evidence that NK1.1+ T cells in the liver are thymus dependent and can arise in the thymus from fetal liver precursor cells. We show that the class I+ (CD1d+) cell type necessary to select NK1.1+ T cells can originate from TCRalpha-/- precursors but not from TCRbeta-/- precursors, indicating that the selecting cell is a CD4+CD8+ thymocyte. 5-Bromo-2'-deoxyuridine-labeling experiments suggest that the thymic NK1.1+ T cell population arises from proliferating precursor cells, but is a mostly sessile population that turns over very slowly. Since liver NK1.1+ T cells incorporate 5-bromo-2'-deoxyuridine more rapidly than thymic NK1.1+ T cells, it appears that liver NK1.1+ T cells either represent a subset of thymic NK1.1+ T cells or are induced to proliferate after having left the thymus. The results indicate that NK1.1+ T cells, like conventional T cells, arise in the thymus where they are selected by interactions with restricting molecules.
authors.affiliation: Department of Molecular and Cell Biology and Cancer Research Laboratory, University of California, Berkeley, CA 94720, USA.
authors.forename: M C
authors.initials: MC
authors.lastname: Coles
authors.forename: D H
authors.initials: DH
authors.lastname: Raulet
mesh_terms: D000818:Animals; D000941:Antigens / Q000096:biosynthesis*; D000950:Antigens, Ly; D000954:Antigens, Surface; D001973:Bromodeoxyuridine / Q000378:metabolism; D015704:CD4 Antigens / Q000096:biosynthesis*; D016827:CD8 Antigens / Q000096:biosynthesis*; D002454:Cell Differentiation / Q000235:genetics / Q000276:immunology; D005434:Flow Cytometry; D015395:Histocompatibility Antigens Class I / Q000235:genetics / Q000378:metabolism*; D007700:Kinetics; D037181:Lectins, C-Type; D008099:Liver / Q000166:cytology / Q000276:immunology* / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D008819:Mice, Nude; D055651:NK Cell Lectin-Like Receptor Subfamily B; D014176:Protein Biosynthesis; D011506:Proteins; D016693:Receptors, Antigen, T-Cell, alpha-beta / Q000172:deficiency / Q000235:genetics / Q000276:immunology; D016176:T-Lymphocyte Subsets / Q000166:cytology / Q000276:immunology* / Q000378:metabolism*; D013950:Thymus Gland / Q000166:cytology / Q000276:immunology* / Q000378:metabolism; D001613:beta 2-Microglobulin / Q000172:deficiency / Q000235:genetics / Q000276:immunology
chemical_list: D000941:Antigens; D000950:Antigens, Ly; D000954:Antigens, Surface; D015704:CD4 Antigens; D016827:CD8 Antigens; D015395:Histocompatibility Antigens Class I; C527211:Klrb1c protein, mouse; D037181:Lectins, C-Type; D055651:NK Cell Lectin-Like Receptor Subfamily B; D011506:Proteins; D016693:Receptors, Antigen, T-Cell, alpha-beta; D001613:beta 2-Microglobulin; D001973:Bromodeoxyuridine