title: CD69 cell surface expression identifies developing thymocytes which audition for T cell antigen receptor-mediated positive selection.
abstract: CD69, an 'activation marker' that is rapidly induced on mature T cells after stimulation through the T cell antigen receptor (TCR) was found to be expressed on approximately 10% of normal thymocytes. All of these CD69+ thymocytes express alpha beta TCR, and they include both TCRlowCD4+CD8+ and TCRhighCD4+CD8- or CD4-CD8+ thymocytes. The CD69+ cells can be further segregated into heat-stable antigen (HSA)+TCRlow, HSA+TCRhigh and HSA-TCRhigh thymocyte populations. None of CD69+ cells express the mature T cell marker Qa-2. Thus CD69+ cells present in vivo appear phenotypically to represent transitional cell populations between immature TCRlowHSA+Qa-2-double-positive cells and mature TCRhighHSA-QA-2+ single-positive cells. In addition, TCR engagement by MHC molecules is required for CD69 expression in the thymus. Taken together, the CD69+ thymocytes appear to represent the cells auditioning in positive selection process or they are the cells that have been positively selected recently. Analysis of a TCR transgenic mouse model revealed an increased number of CD69+ thymocytes in a positively selecting thymus, whereas no CD69+ transgenic TCR+ thymocytes were observed in the non-selecting thymus. Based on the results of this study, we suggest that the surface expression of CD69 serves as a useful marker to identify and trace those thymocytes that are engaged in the TCR-mediated positive selection process in the thymus.
authors.affiliation: Department of Immunology, Faculty of Medicine, University of Tokyo, Japan.
authors.forename: I
authors.initials: I
authors.lastname: Yamashita
authors.forename: T
authors.initials: T
authors.lastname: Nagata
authors.forename: T
authors.initials: T
authors.lastname: Tada
authors.forename: T
authors.initials: T
authors.lastname: Nakayama
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal; D015703:Antigens, CD / Q000276:immunology*; D000945:Antigens, Differentiation, T-Lymphocyte / Q000276:immunology*; D015415:Biomarkers; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology*; D005434:Flow Cytometry; D016130:Immunophenotyping; D037181:Lectins, C-Type; D008213:Lymphocyte Activation / Q000276:immunology; D051379:Mice; D008810:Mice, Inbred C57BL; D008808:Mice, Inbred CBA; D016693:Receptors, Antigen, T-Cell, alpha-beta / Q000276:immunology*; D013154:Spleen / Q000276:immunology; D050378:T-Lymphocytes, Regulatory / Q000276:immunology*; D013950:Thymus Gland / Q000276:immunology; D000099192:CD69 Antigens
chemical_list: D000911:Antibodies, Monoclonal; D015703:Antigens, CD; D000945:Antigens, Differentiation, T-Lymphocyte; D015415:Biomarkers; D037181:Lectins, C-Type; D016693:Receptors, Antigen, T-Cell, alpha-beta; D000099192:CD69 Antigens