title: Effect of phorbol ester and calcium ionophore on human thymocytes.
abstract: Positive selection of immature thymocytes is a developmental process in which TCR ligation with low avidity induces generation of mature T cells. In mouse thymocytes, CD4(+)8(+) double-positive (DP) cells which were treated with a proper combination of calcium ionophore ionomycin and phorbol 12-myristate 13-acetate (PMA) have been reported to differentiate into CD4 single positive cells. However, in human thymocytes the effects of PMA and ionomycin have remained unclear. Here we report that DP cells that were treated with PMA and ionomycin up-regulated bcl-2 and down-regulated CD1 expression. However, CD3 expression remained low. This treatment induced prolonged CD4 down-regulation in DP cells which was an effect also seen in mature peripheral blood T cells. PMA/ionomycin-treated DP cells showed high cell proliferation and resistance to dexamethasone-induced apoptosis. These results indicate that PKC activation and calcium elevation may be part of the biochemical signals that induce positive selection of human DP cells and the system described in this paper may be a useful model to study the signals involved in the selection of human thymocytes.
authors.affiliation: Department of Surgery, Nagoya City, University Medical School, Kawasumi 1, Mizuho-ku, 467-8601, Nagoya, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Tanahashi
authors.forename: T
authors.initials: T
authors.lastname: Yokoyama
authors.forename: Y
authors.initials: Y
authors.lastname: Kobayashi
authors.forename: Y
authors.initials: Y
authors.lastname: Yamakawa
authors.forename: M
authors.initials: M
authors.lastname: Maeda
authors.forename: Y
authors.initials: Y
authors.lastname: Fujii
mesh_terms: D018949:Antigens, CD1 / Q000276:immunology; D017209:Apoptosis / Q000187:drug effects; D015704:CD4 Antigens / Q000032:analysis; D016827:CD8 Antigens / Q000032:analysis; D002455:Cell Division / Q000187:drug effects; D002470:Cell Survival; D002478:Cells, Cultured; D003907:Dexamethasone / Q000494:pharmacology; D004306:Dose-Response Relationship, Immunologic; D005434:Flow Cytometry; D006801:Humans; D015759:Ionomycin / Q000494:pharmacology*; D007476:Ionophores / Q000494:pharmacology*; D008213:Lymphocyte Activation / Q000187:drug effects; D010703:Phorbol Esters / Q000494:pharmacology*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000032:analysis / Q000096:biosynthesis; D013601:T-Lymphocytes / Q000187:drug effects* / Q000276:immunology; D013950:Thymus Gland / Q000187:drug effects* / Q000276:immunology
chemical_list: D018949:Antigens, CD1; D015704:CD4 Antigens; D016827:CD8 Antigens; D007476:Ionophores; D010703:Phorbol Esters; D019253:Proto-Oncogene Proteins c-bcl-2; D015759:Ionomycin; D003907:Dexamethasone