title: Differential expression of APO-1 on human thymocytes: implications for negative selection?
abstract: Negative selection during T cell ontogeny involves selective induction of apoptosis in thymocytes. In peripheral lymphoid cells, apoptosis may be mediated via the APO-1 pathway. Here we report that APO-1 is constitutively expressed on the vast majority of human thymocytes but down-regulated at a mature stage of thymocyte development (TCR(hi)). This stage of development is characterized by CD28hi, CD44hi, CD69hi and up-regulation of Bcl-2 protein. We define a new thymocyte subpopulation that expresses high levels of APO-1 and intermediate levels of T cell receptor alpha/beta (TCR(im)/APO-1hi). The TCR(im)/APO-1hi population contains a large fraction of dead cells, suggesting that the APO-1 pathway may be involved in negative selection of at least a fraction of thymocytes after intrathymic activation.
authors.affiliation: Tumorimmunology Program/Division of Immunogenetics, German Cancer Research Center, Heidelberg.
authors.forename: K M
authors.initials: KM
authors.lastname: Debatin
authors.forename: D
authors.initials: D
authors.lastname: Süss
authors.forename: P H
authors.initials: PH
authors.lastname: Krammer
mesh_terms: D000954:Antigens, Surface / Q000378:metabolism*; D017209:Apoptosis; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology; D016827:CD8 Antigens / Q000032:analysis; D002454:Cell Differentiation; D006801:Humans; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2; D016693:Receptors, Antigen, T-Cell, alpha-beta / Q000378:metabolism; D016176:T-Lymphocyte Subsets / Q000166:cytology*; D013950:Thymus Gland / Q000166:cytology*; D019014:fas Receptor
chemical_list: D000954:Antigens, Surface; D016827:CD8 Antigens; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D016693:Receptors, Antigen, T-Cell, alpha-beta; D019014:fas Receptor