In vitro thymocyte differentiation in MHC class I-negative Xenopus larvae.
CTX is a surface antigen whose expression in larval and adult Xenopus is primarily restricted to MHC class I-negative immature cortical thymocytes. In adult Xenopus, surface expression of CTX marks a population of MHC class I(-) CD8(+) immature thymocytes that appears to be the equivalent of the mammalian CD4CD8 double positive subset. The present study reveals that transient in vitro exposure of immature CTX(+) thymocytes from MHC class I-negative tadpoles to suboptimal mitogenic concentrations of phorbol ester (PMA) plus ionomycin, induces larval cells to differentiate into more mature T-lymphoblasts that express high level of surface CD5 and CD45. These T-lymphoblasts have downregulated CTX, Rag 1 and TdT genes, whereas TCR-beta genes remain actively transcribed. Signaling induced by PMA/ionomycin modulates both class I and class II expression of MHC class I/II-negative larval thymocytes. This study also reveals that larval T-lymphoblasts are composed of two distinct subsets: CD5(high)CD8(-) and CD5 (high)CD8 (high).
Department of Microbiology and Immunology, University of Rochester Medical Center, Box 672, 601 Elmwood Avenue, Rochester, NY 14642, USA. robert@uhura.cc.rochester.edu
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J
Robert
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M
Sung
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N
Cohen
D000818:Animals; D021461:Animals, Outbred Strains; D000945:Antigens, Differentiation, T-Lymphocyte; D018956:CD5 Antigens / Q000096:biosynthesis / Q000235:genetics; D016827:CD8 Antigens / Q000096:biosynthesis / Q000235:genetics; D002454:Cell Differentiation / Q000187:drug effects; D004253:DNA Nucleotidylexotransferase / Q000096:biosynthesis / Q000235:genetics; D005786:Gene Expression Regulation / Q000187:drug effects; D005805:Genes, MHC Class I; D005802:Genes, MHC Class II; D015395:Histocompatibility Antigens Class I / Q000032:analysis*; D000949:Histocompatibility Antigens Class II / Q000096:biosynthesis; D018398:Homeodomain Proteins / Q000096:biosynthesis / Q000235:genetics; D016130:Immunophenotyping; D015759:Ionomycin / Q000494:pharmacology; D007814:Larva; D017493:Leukocyte Common Antigens / Q000096:biosynthesis / Q000235:genetics; D008565:Membrane Proteins / Q000096:biosynthesis* / Q000235:genetics; D016693:Receptors, Antigen, T-Cell, alpha-beta / Q000096:biosynthesis / Q000235:genetics; D016176:T-Lymphocyte Subsets / Q000166:cytology* / Q000187:drug effects / Q000276:immunology; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D013950:Thymus Gland / Q000166:cytology / Q000254:growth & development*; D029867:Xenopus Proteins; D014982:Xenopus laevis / Q000254:growth & development / Q000276:immunology*
D000945:Antigens, Differentiation, T-Lymphocyte; D018956:CD5 Antigens; D016827:CD8 Antigens; D015395:Histocompatibility Antigens Class I; D000949:Histocompatibility Antigens Class II; D018398:Homeodomain Proteins; D008565:Membrane Proteins; D016693:Receptors, Antigen, T-Cell, alpha-beta; D029867:Xenopus Proteins; C099384:ctx-A protein, Xenopus; C064658:RAG-1 protein; D015759:Ionomycin; D004253:DNA Nucleotidylexotransferase; D017493:Leukocyte Common Antigens; D013755:Tetradecanoylphorbol Acetate