title: Downregulated expression of Ly-6-ThB on developing T cells marks CD4+CD8+ subset undergoing selection in the thymus.
abstract: Interaction of TCRs on CD4+CD8+ immature T cell with MHC-peptide complexes on stromal cells is required for positive and negative selection in the thymus. Identification and characterization of a subpopulation of CD4+CD8+ thymocytes undergoing selection in the thymus will aid in understanding the mechanisms underlying lineage commitment and thymic selection. Herein, we describe the expression of Ly-6 ThB on developing thymocytes. The majority of CD4+CD8+ thymocytes express Ly-6 ThB at high levels. Its expression is downregulated in a subset of CD4+CD8+ thymocytes as well as in mature CD4+CD8- and CD4-CD8+ T cells. More importantly, interaction of TCR/coreceptor with the self-MHC-peptide contributes to the downregulation of ThB expression on developing thymocytes. These findings indicate that downregulation of ThB on CD4+CD8+ thymocytes identifies a unique subset (CD4+CD8+ThBneg-low) of thymocytes that has received the initial signals for thymic selection but have not yet downregulated the CD4 and CD8 cell surface expression. In addition, these results also indicate that a high frequency (approximately 20-40%) of CD4+CD8+ immature thymocytes receive these initial signals during thymic selection.
authors.affiliation: Department of Cellular Biology, University of Georgia, Athens 30602, USA.
authors.forename: J T
authors.initials: JT
authors.lastname: Reese
authors.forename: H
authors.initials: H
authors.lastname: Mehta
authors.forename: C H
authors.initials: CH
authors.lastname: Chappell
authors.forename: A
authors.initials: A
authors.lastname: Bamezai
mesh_terms: D000818:Animals; D000950:Antigens, Ly; D000951:Antigens, Neoplasm; D000954:Antigens, Surface / Q000032:analysis*; D015704:CD4 Antigens / Q000032:analysis*; D016827:CD8 Antigens / Q000032:analysis*; D015536:Down-Regulation; D058851:GPI-Linked Proteins; D015395:Histocompatibility Antigens Class I / Q000032:analysis; D000949:Histocompatibility Antigens Class II / Q000032:analysis; D051379:Mice; D008806:Mice, Inbred AKR; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D016176:T-Lymphocyte Subsets / Q000737:chemistry*; D013950:Thymus Gland / Q000166:cytology*
chemical_list: D000950:Antigens, Ly; D000951:Antigens, Neoplasm; D000954:Antigens, Surface; D015704:CD4 Antigens; D016827:CD8 Antigens; D058851:GPI-Linked Proteins; D015395:Histocompatibility Antigens Class I; D000949:Histocompatibility Antigens Class II; C035271:Ly6d protein, mouse