title: Autocrine TNF is critical for the survival of human dendritic cells by regulating BAK, BCL-2, and FLIPL.
abstract: The life span of dendritic cells (DCs) is determined by the balance of pro- and antiapoptotic proteins. In this study, we report that serum-free cultured human monocyte-derived DCs after TLR stimulation with polyinosinic acid-polycytidylic acid or LPS underwent apoptosis, which was correlated with low TNF production. Apoptosis was prevented by the addition of exogenous TNF or by concomitant stimulation with R-848, which strongly amplified endogenous TNF production. Neutralization of TNF confirmed that DC survival was mediated by autocrine TNF induced either by stimulation with R-848 or by ligation of CD40. DCs stimulated by polyinosinic acid-polycytidylic acid or IFN-β, another known inducer of DC apoptosis, were characterized by high levels and activation of the proapoptotic protein BAK. The ratio of antiapoptotic BCL-2 to BAK correlated best with the survival of activated DCs. Addition of TNF increased this ratio but had little effect on BAX and XIAP. Knockdown experiments using small interfering RNAs confirmed that the survival of activated and also of immature DCs was regulated by BAK and showed that TNF was protective only in the presence of FLIP(L). Together, our data demonstrate that the survival of DCs during differentiation and activation depends on autocrine TNF and that the inhibition of BAK plays an important role in this process.
authors.affiliation: Laboratory of Cellular Therapy, Department of Hematology and Oncology, Children's University Hospital, Friedrich-Alexander-Universität Erlangen-Nürnberg, Klinikum Erlangen, Erlangen 91054, Germany.
authors.forename: Manfred
authors.initials: M
authors.lastname: Lehner
authors.forename: Beate
authors.initials: B
authors.lastname: Kellert
authors.forename: Julia
authors.initials: J
authors.lastname: Proff
authors.forename: Martina A
authors.initials: MA
authors.lastname: Schmid
authors.forename: Philip
authors.initials: P
authors.lastname: Diessenbacher
authors.forename: Armin
authors.initials: A
authors.lastname: Ensser
authors.forename: Jan
authors.initials: J
authors.lastname: Dörrie
authors.forename: Niels
authors.initials: N
authors.lastname: Schaft
authors.forename: Martin
authors.initials: M
authors.lastname: Leverkus
authors.forename: Eckhart
authors.initials: E
authors.lastname: Kämpgen
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Holter
mesh_terms: D051017:Apoptosis Regulatory Proteins / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000502:physiology*; D019898:Autocrine Communication / Q000276:immunology*; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein / Q000096:biosynthesis / Q000378:metabolism* / Q000502:physiology; D002452:Cell Count; D002454:Cell Differentiation / Q000276:immunology; D002470:Cell Survival / Q000276:immunology; D002478:Cells, Cultured; D003713:Dendritic Cells / Q000166:cytology* / Q000276:immunology* / Q000378:metabolism; D006801:Humans; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000096:biosynthesis / Q000378:metabolism*; D014409:Tumor Necrosis Factor-alpha / Q000008:administration & dosage / Q000096:biosynthesis / Q000502:physiology*; D050998:bcl-2 Homologous Antagonist-Killer Protein / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000378:metabolism*
chemical_list: D051017:Apoptosis Regulatory Proteins; C494772:BAK1 protein, human; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein; D019253:Proto-Oncogene Proteins c-bcl-2; D014409:Tumor Necrosis Factor-alpha; D050998:bcl-2 Homologous Antagonist-Killer Protein