title: Precursors of functional MHC class I- or class II-restricted CD8alphaalpha(+) T cells are positively selected in the thymus by agonist self-peptides.
abstract: The origin and specificity of alphabeta TCR(+) T cells that express CD8alphaalpha have been controversial issues. Here we provide direct evidence that precursors of functional CD8alphaalpha T cells are positively selected in the thymus in the presence of agonist self-peptides. Like conventional positive selection, this agonist selection process requires functional TCR alpha-CPM, whereas it is independent of CD8beta expression. Furthermore, CD8alphaalpha expression on mature, agonist-selected T cells does not imply selection by MHC class I, and CD8alphaalpha(+) T cells can be either class I or class II restricted. Our data define a distinct agonist-dependent, positive selection process in the thymus, and they suggest a function for CD8alphaalpha distinct from the conventional TCR coreceptor function of CD8alphabeta or CD4.
authors.affiliation: La Jolla Institute for Allergy and Immunology, 10355 Science Center Drive, San Diego, CA 92121, USA.
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Leishman
authors.forename: Laurent
authors.initials: L
authors.lastname: Gapin
authors.forename: Myriam
authors.initials: M
authors.lastname: Capone
authors.forename: Ed
authors.initials: E
authors.lastname: Palmer
authors.forename: H Robson
authors.initials: HR
authors.lastname: MacDonald
authors.forename: Mitchell
authors.initials: M
authors.lastname: Kronenberg
authors.forename: Hilde
authors.initials: H
authors.lastname: Cheroutre
mesh_terms: D000818:Animals; D017951:Antigen Presentation; D016827:CD8 Antigens / Q000276:immunology*; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology*; D015395:Histocompatibility Antigens Class I / Q000276:immunology; D000949:Histocompatibility Antigens Class II / Q000276:immunology; D051379:Mice; D008822:Mice, Transgenic; D013950:Thymus Gland / Q000276:immunology*
chemical_list: D016827:CD8 Antigens; C409469:CD8 antigen, alpha chain; D015395:Histocompatibility Antigens Class I; D000949:Histocompatibility Antigens Class II