title: CD45 enhances positive selection and is expressed at a high level in large, cycling, positively selected CD4+CD8+ thymocytes.
abstract: T-cell development is arrested at the CD4+CD8+ (DP; double-positive) stage of thymocyte development in CD45 null mice. However, the mechanism by which CD45 participates in the positive selection of T cells remains to be investigated. In this report we describe a DP thymocyte population that associates positive selection with expression of high levels of CD45, CD4 and CD8. DP thymocytes of this phenotype are large, cycling cells and represent approximately 20% of DP thymocytes in normal mice. In mice expressing a transgenic T-cell receptor (TCR) specific for the male antigen presented by H-2Db (H-Y TCR), the up-regulation of TCR, CD5 and CD69 in this large DP population occurred in a major histocompatibility complex (MHC)-restricted manner. To investigate further the role of CD45 in positive selection, we determined whether thymocytes that expressed a transgenic CD45RO molecule under the control of the proximal lck promoter can influence the positive selection of T cells in H-Y TCR transgenic mice. It was found that in female H-Y TCR transgenic mice, MHC-restricted positive selection of CD4- CD8+ H-Y TCR+ thymocytes was enhanced by increased CD45RO expression. Thus, CD45 increases the efficacy of positive selection of CD4- CD8+ thymocytes that express H-Y TCR.
authors.affiliation: Biomedical Research Centre, University of British Columbia, Vancouver, Canada.
authors.forename: C J
authors.initials: CJ
authors.lastname: Ong
authors.forename: J P
authors.initials: JP
authors.lastname: Dutz
authors.forename: D
authors.initials: D
authors.lastname: Chui
authors.forename: H S
authors.initials: HS
authors.lastname: Teh
authors.forename: J D
authors.initials: JD
authors.lastname: Marth
mesh_terms: D000818:Animals; D015703:Antigens, CD / Q000032:analysis; D000945:Antigens, Differentiation, T-Lymphocyte / Q000032:analysis; D017252:CD3 Complex / Q000032:analysis; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology*; D018956:CD5 Antigens / Q000032:analysis; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology*; D005805:Genes, MHC Class I / Q000276:immunology; D037181:Lectins, C-Type; D017493:Leukocyte Common Antigens / Q000032:analysis / Q000276:immunology*; D008297:Male; D051379:Mice; D008815:Mice, Inbred Strains; D008822:Mice, Transgenic; D011948:Receptors, Antigen, T-Cell / Q000276:immunology; D016196:S Phase / Q000276:immunology; D013950:Thymus Gland / Q000276:immunology*; D015854:Up-Regulation / Q000276:immunology; D000099192:CD69 Antigens
chemical_list: D015703:Antigens, CD; D000945:Antigens, Differentiation, T-Lymphocyte; D017252:CD3 Complex; D018956:CD5 Antigens; D037181:Lectins, C-Type; D017493:Leukocyte Common Antigens; D011948:Receptors, Antigen, T-Cell; D000099192:CD69 Antigens