title: Activation and 'deletion' of self-reactive mature and immature T cells during ontogeny of Mls-1a mice: implications for neonatal tolerance induction.
abstract: We assessed the kinetics of V beta 6+ T cell elimination in the lymph nodes and thymus during Mls-1a mouse ontogeny. Our results suggest that induction of tolerance to Mls-1a antigens involves mechanisms other than clonal deletion of immature T cells in the thymus. Mature CD4+CD8- (CD4SP) T cells were affected by Mls-1a antigens earlier than immature thymocyte populations. Up to 2 weeks after birth, reduced frequencies of V beta 6+ T cells were detected only in CD4SP cells from the thymus and lymph nodes, and generation of CD4SP cells in the thymus was blocked at least 1 week earlier than that of their CD4+CD8loTCRhi immature precursors. The number of V beta 6+CD4SP T cells increased during the first 2 weeks of life and remained constant thereafter. We thus found no evidence of deletion of mature V beta 6+CD4SP T cells, as the reduced frequencies in adult mice can be attributed to the dilution of previously generated cells in lymphoid organs of growing mice, which increase in cellularity after birth. V beta 6+CD4+ T cells were activated in vivo shortly after birth, as shown by a selective increase in IL-2 receptor alpha chain expression in the thymus and lymph nodes from day 0 to day 2 after birth. It is therefore likely that endogenous expression of Mls-1a antigen shortly after birth activates V beta 6+CD4SP T cells and renders them anergic. This process of tolerance induction may precede the clonal deletion of immature T cells in the thymus, described in the adult mouse.
authors.affiliation: INSERM U345, CNRS UA122, Institut Necker, Paris, France.
authors.forename: G
authors.initials: G
authors.lastname: Marodon
authors.forename: B
authors.initials: B
authors.lastname: Rocha
mesh_terms: D000818:Animals; D000831:Animals, Newborn / Q000254:growth & development / Q000276:immunology*; D002454:Cell Differentiation / Q000276:immunology; D017637:Clonal Deletion / Q000276:immunology*; D005434:Flow Cytometry; D008198:Lymph Nodes / Q000254:growth & development; D008213:Lymphocyte Activation / Q000276:immunology*; D008221:Lymphoid Tissue / Q000166:cytology / Q000254:growth & development*; D051379:Mice; D008810:Mice, Inbred C57BL; D008811:Mice, Inbred DBA; D016744:Minor Lymphocyte Stimulatory Loci / Q000235:genetics; D016693:Receptors, Antigen, T-Cell, alpha-beta / Q000096:biosynthesis / Q000276:immunology; D015375:Receptors, Interleukin-2 / Q000096:biosynthesis; D013601:T-Lymphocytes / Q000276:immunology*; D013950:Thymus Gland / Q000254:growth & development
chemical_list: D016693:Receptors, Antigen, T-Cell, alpha-beta; D015375:Receptors, Interleukin-2