title: Programmed death of autoreactive thymocytes.
abstract: T lymphocytes bearing high-affinity T-cell receptors (TCR) for self-antigens are clonally deleted during thymus development. Several recent studies have identified variable domains of the beta-chain of the TCR that are specifically deleted in vivo in mouse strains that express major histocompatibility complex class II molecules in addition to poorly defined self-antigens, including those encoded by the Mls-1a and Mls-2a loci. Deletion of autoreactive cells in these systems occurs in the thymus, and antibody blocking experiments in vivo have implicated the phenotypically immature CD4+CD8+ 'cortical' subset as the target population for clonal deletion. Similarly, studies with transgenic mice bearing autoreactive TCR have provided independent evidence that clonal deletion occurs at the CD4+CD8+ stage of development. But none of these studies directly identified dying autoreactive cells, and the circumstances leading to deletion remain unclear. Here we report that neonatal thymus contains a significant population of phenotypically mature CD4+CD8- cells bearing autoreactive TCR. When placed in short-term culture, a large proportion (60%) of these autoreactive cells die selectively. Furthermore, their death can be prevented by inhibitors of macromolecule (RNA and protein) synthesis, as is the case for glucocorticoid-induced death of thymocytes. These data indicate that physiological clonal deletion of autoreactive cells involves 'programmed' cell death, and that it can occur in cells with a mature (CD4+CD8-) surface phenotype.
authors.affiliation: Ludwig Institute for Cancer Research, Epalinges, Switzerland.
authors.forename: H R
authors.initials: HR
authors.lastname: MacDonald
authors.forename: R K
authors.initials: RK
authors.lastname: Lees
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D001324:Autoantigens / Q000276:immunology; D015704:CD4 Antigens / Q000032:analysis; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D003513:Cycloheximide / Q000494:pharmacology; D003609:Dactinomycin / Q000494:pharmacology; D015759:Ionomycin / Q000494:pharmacology; D007700:Kinetics; D051379:Mice; D008807:Mice, Inbred BALB C; D008815:Mice, Inbred Strains; D013601:T-Lymphocytes / Q000166:cytology* / Q000187:drug effects / Q000276:immunology; D013696:Temperature; D013997:Time Factors
chemical_list: D001324:Autoantigens; D015704:CD4 Antigens; D003609:Dactinomycin; D015759:Ionomycin; D003513:Cycloheximide