title: Late thymectomy in Xenopus tadpoles reveals a population of T cells that persists through metamorphosis.
abstract: To investigate the persistence of larval T lymphocytes in the adult period, tadpoles of the South African clawed frog, Xenopus laevis, were allowed to develop to prometamorphic stages 57-58 and thymectomized (Tx). Thymectomy at this stage allows for maximal expansion of the larval T cell population but prevents emergence of the adult T cell population. Using a T cell-specific monoclonal antibody (mAb) which recognizes the XTLA-1 determinant, we examined the absolute numbers of thymic and splenic T cells expressing XTLA-1 in normal tadpoles, postmetamorphic Tx frogs, and intact age-matched adult frogs. A small, but measurable, number of larvally-derived XTLA-1+ cells persists through metamorphosis. By simultaneously staining with a mAb specific for class II major histocompatibility (MHC) antigens, we determined the phenotype of the persisting XTLA-1+ cells in the Tx frogs. Like XTLA-1+ splenocytes in intact adult controls which are predominantly class II+, most XTLA-1+ cells in Tx adults also express class II. In contrast, most XTLA-1+ cells in the tadpole are class II-. This suggests that a small population of class II+ larval T cells survives metamorphic transition to become a long-lived population in the adult. Alternatively, some class II- larval T cells may express class II in the adult period.
authors.affiliation: Department of Microbiology and Immunology, Vanderbilt University School of Medicine, Nashville, TN 37232, USA.
authors.forename: L A
authors.initials: LA
authors.lastname: Rollins-Smith
authors.forename: D A
authors.initials: DA
authors.lastname: Needham
authors.forename: A T
authors.initials: AT
authors.lastname: Davis
authors.forename: P J
authors.initials: PJ
authors.lastname: Blair
mesh_terms: D000818:Animals; D000945:Antigens, Differentiation, T-Lymphocyte / Q000096:biosynthesis; D002454:Cell Differentiation / Q000276:immunology; D003208:Concanavalin A / Q000494:pharmacology; D000949:Histocompatibility Antigens Class II / Q000096:biosynthesis; D007814:Larva / Q000254:growth & development / Q000276:immunology / Q000378:metabolism; D008213:Lymphocyte Activation; D008675:Metamorphosis, Biological / Q000276:immunology*; D010835:Phytohemagglutinins / Q000494:pharmacology; D013154:Spleen / Q000276:immunology; D016176:T-Lymphocyte Subsets / Q000276:immunology / Q000378:metabolism / Q000502:physiology*; D013934:Thymectomy; D014982:Xenopus laevis / Q000254:growth & development* / Q000276:immunology*
chemical_list: D000945:Antigens, Differentiation, T-Lymphocyte; D000949:Histocompatibility Antigens Class II; D010835:Phytohemagglutinins; D003208:Concanavalin A