title: MEK activity regulates negative selection of immature CD4+CD8+ thymocytes.
abstract: CD4+CD8+ thymocytes are either positively selected and subsequently mature to CD4 single positive (SP) or CD8 SP T cells, or they die by apoptosis due to neglect or negative selection. This clonal selection is essential for establishing a functional self-restricted T cell repertoire. Intracellular signals through the three known mitogen-activated protein (MAP) kinase pathways have been shown to selectively guide positive or negative selection. Whereas the c-Jun N-terminal kinase and p38 MAP kinase regulate negative selection of thymocytes, the extracellular signal-regulated kinase (ERK) pathway is required for positive selection and T cell lineage commitment. In this paper, we show that the MAP/ERK kinase (MEK)-ERK pathway is also involved in negative selection. Thymocytes from newborn TCR transgenic mice were cultured with TCR/CD3epsilon-specific Abs or TCR-specific agonist peptides to induce negative selection. In the presence of the MEK-specific pharmacological inhibitors PD98059 or UO126, cell recovery was enhanced and deletion of DP thymocytes was drastically reduced. Furthermore, development of CD4 SP T cells was blocked, but differentiation of mature CD8 SP T cells proceeded in the presence of agonist peptides when MEK activity was blocked. Thus, our data indicate that the outcome between positively and negatively selecting signals is critically dependent on MEK activity.
authors.affiliation: Institute of Virology and Immunobiology, Würzburg, Germany. Bommhardt@vim.uni-wuerzburg.de
authors.forename: U
authors.initials: U
authors.lastname: Bommhardt
authors.forename: Y
authors.initials: Y
authors.lastname: Scheuring
authors.forename: C
authors.initials: C
authors.lastname: Bickel
authors.forename: R
authors.initials: R
authors.lastname: Zamoyska
authors.forename: T
authors.initials: T
authors.lastname: Hünig
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects / Q000276:immunology; D002070:Butadienes / Q000494:pharmacology; D015704:CD4 Antigens / Q000096:biosynthesis*; D016827:CD8 Antigens / Q000096:biosynthesis*; D018414:CD8-Positive T-Lymphocytes / Q000166:cytology / Q000201:enzymology / Q000276:immunology / Q000378:metabolism; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism; D002454:Cell Differentiation / Q000187:drug effects / Q000276:immunology; D017637:Clonal Deletion / Q000187:drug effects; D004789:Enzyme Activation / Q000187:drug effects / Q000276:immunology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D005419:Flavonoids / Q000494:pharmacology; D000949:Histocompatibility Antigens Class II / Q000276:immunology; D048031:JNK Mitogen-Activated Protein Kinases; D048728:MAP Kinase Kinase Kinase 1; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D009570:Nitriles / Q000494:pharmacology; D009924:Organ Culture Techniques; D010446:Peptide Fragments / Q000819:agonists / Q000276:immunology; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D017260:Receptor-CD3 Complex, Antigen, T-Cell / Q000276:immunology; D016176:T-Lymphocyte Subsets / Q000166:cytology / Q000201:enzymology* / Q000276:immunology* / Q000378:metabolism; D013950:Thymus Gland / Q000166:cytology* / Q000201:enzymology / Q000276:immunology / Q000378:metabolism; D014758:Viral Core Proteins / Q000819:agonists / Q000276:immunology; D048051:p38 Mitogen-Activated Protein Kinases
chemical_list: D000911:Antibodies, Monoclonal; D002070:Butadienes; D015704:CD4 Antigens; D016827:CD8 Antigens; D004791:Enzyme Inhibitors; D005419:Flavonoids; D000949:Histocompatibility Antigens Class II; D009570:Nitriles; D010446:Peptide Fragments; D017260:Receptor-CD3 Complex, Antigen, T-Cell; C113580:U 0126; D014758:Viral Core Proteins; D017346:Protein Serine-Threonine Kinases; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D048728:MAP Kinase Kinase Kinase 1; C482578:Map3k1 protein, mouse; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one