title: Fas/Fas ligand interactions promote activation-induced cell death of NK T lymphocytes.
abstract: NKT cells are a versatile population whose immunoregulatory functions are modulated by their microenvironment. We demonstrate herein that in addition to their IFN-gamma production, NKT lymphocytes stimulated with IL-12 plus IL-18 in vitro underwent activation in terms of CD69 expression, blast transformation, and proliferation. Yet they were unable to survive in culture because, once activated, they were rapidly eliminated by apoptosis, even in the presence of their survival factor IL-7. This process was preceded by up-regulation of Fas (CD95) and Fas ligand expression in response to IL-12 plus IL-18 and was blocked by zVAD, a large spectrum caspase inhibitor, as well as by anti-Fas ligand mAb, suggesting the involvement of the Fas pathway. In accordance with this idea, NKT cells from Fas-deficient C57BL/6-lpr/lpr mice did not die in these conditions, although they shared the same features of cell activation as their wild-type counterpart. Activation-induced cell death occurred also after TCR engagement in vivo, since NKT cells became apoptotic after injection of their cognate ligand, alpha-galactosylceramide, in wild-type, but not in Fas-deficient, mice. Taken together, our data provide the first evidence for a new Fas-dependent mechanism allowing the elimination of TCR-dependent or -independent activated NKT cells, which are potentially dangerous to the organism.
authors.affiliation: Centre National de la Recherche Scientifique, Unité Mixte de Recherche 8603, Université René Descartes, Paris V, Hôpital Necker, Paris, France. leite.morales@necker.fr
authors.forename: M C
authors.initials: MC
authors.lastname: Leite-de-Moraes
authors.forename: A
authors.initials: A
authors.lastname: Herbelin
authors.forename: C
authors.initials: C
authors.lastname: Gouarin
authors.forename: Y
authors.initials: Y
authors.lastname: Koezuka
authors.forename: E
authors.initials: E
authors.lastname: Schneider
authors.forename: M
authors.initials: M
authors.lastname: Dy
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000276:immunology*; D004357:Drug Synergism; D053222:Fas Ligand Protein; D005699:Galactosylceramides / Q000378:metabolism / Q000494:pharmacology; D018664:Interleukin-12 / Q000494:pharmacology; D020382:Interleukin-18 / Q000494:pharmacology; D007694:Killer Cells, Natural / Q000166:cytology* / Q000187:drug effects / Q000276:immunology / Q000378:metabolism; D008024:Ligands; D008213:Lymphocyte Activation / Q000187:drug effects; D008562:Membrane Glycoproteins / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D019463:Mice, Inbred MRL lpr; D008817:Mice, Mutant Strains; D016176:T-Lymphocyte Subsets / Q000166:cytology* / Q000187:drug effects / Q000276:immunology / Q000378:metabolism; D019014:fas Receptor / Q000378:metabolism* / Q000502:physiology
chemical_list: D053222:Fas Ligand Protein; C505658:Fasl protein, mouse; D005699:Galactosylceramides; D020382:Interleukin-18; D008024:Ligands; D008562:Membrane Glycoproteins; D019014:fas Receptor; D018664:Interleukin-12