Abstract
The expression of tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) and TRAIL receptors was investigated in resting and cytokine-activated purified primary human natural killer (NK) and CD8(+) T cells. Resting NK and CD8(+) T cells expressed the mRNA for all TRAIL receptors, but TRAIL-R4 was the only receptor clearly detectable on the surface of both cell types. NK cells were activated by interleukin 2 (IL-2) or IL-15, whereas CD8(+) T cells were activated by phytohemagglutinin (PHA) + IL-2 followed by IL-2 alone for up to 10 days. On activation, both cell types rapidly expressed TRAIL-R2 and TRAIL-R3, whose expression peaked at day 10 of culture. TRAIL-R1, however, was never expressed at any time point examined, whereas the expression of TRAIL-R4, which showed a progressive increase in CD8(+) T cells, remained constant in NK cells. Notwithstanding the expression of TRAIL-R2, recombinant TRAIL did not show any cytotoxic activity on either NK or CD8(+) T cells. Both resting and activated NK and CD8(+) T cells were found to express high levels of the 2 isoforms of c-FLIP (cellular Fas-associated death domain protein [FADD]-like IL-1-converting enzyme [FLICE]-inhibitory protein). Small interference RNA-mediated inhibition of c-FLIP expression in NK cells abrogated their resistance to the apoptotic effect of soluble TRAIL. Thus, once activated the major cytotoxic effector cells are potentially sensitive to TRAIL but are physiologically protected from its apoptotic action by intracellular level of c-FLIP.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Apoptosis Regulatory Proteins
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Apoptosis* / drug effects
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CASP8 and FADD-Like Apoptosis Regulating Protein
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CD8-Positive T-Lymphocytes / cytology
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CD8-Positive T-Lymphocytes / immunology*
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CD8-Positive T-Lymphocytes / metabolism
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Cells, Cultured
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Cytotoxicity, Immunologic / immunology*
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Dactinomycin / pharmacology
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Flow Cytometry
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GPI-Linked Proteins
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Humans
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Interleukin-2 / pharmacology
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Intracellular Signaling Peptides and Proteins / genetics
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Intracellular Signaling Peptides and Proteins / metabolism
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Killer Cells, Natural / cytology
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Killer Cells, Natural / drug effects
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Killer Cells, Natural / immunology*
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Killer Cells, Natural / metabolism
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Lymphocyte Activation*
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Membrane Glycoproteins / genetics
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Membrane Glycoproteins / metabolism*
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Membrane Glycoproteins / pharmacology
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RNA, Messenger / genetics
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RNA, Messenger / metabolism
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RNA, Small Interfering / genetics
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RNA, Small Interfering / metabolism
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Receptors, TNF-Related Apoptosis-Inducing Ligand
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Receptors, Tumor Necrosis Factor / genetics
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Receptors, Tumor Necrosis Factor / immunology
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Receptors, Tumor Necrosis Factor / metabolism*
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Receptors, Tumor Necrosis Factor, Member 10c
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TNF-Related Apoptosis-Inducing Ligand
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Transcription, Genetic / drug effects
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Tumor Necrosis Factor Decoy Receptors
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Tumor Necrosis Factor-alpha / genetics
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Tumor Necrosis Factor-alpha / metabolism*
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Tumor Necrosis Factor-alpha / pharmacology
Substances
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Apoptosis Regulatory Proteins
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CASP8 and FADD-Like Apoptosis Regulating Protein
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CFLAR protein, human
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GPI-Linked Proteins
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Interleukin-2
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Intracellular Signaling Peptides and Proteins
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Membrane Glycoproteins
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RNA, Messenger
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RNA, Small Interfering
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Receptors, TNF-Related Apoptosis-Inducing Ligand
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Receptors, Tumor Necrosis Factor
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Receptors, Tumor Necrosis Factor, Member 10c
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TNF-Related Apoptosis-Inducing Ligand
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TNFRSF10A protein, human
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TNFRSF10B protein, human
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TNFRSF10C protein, human
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TNFSF10 protein, human
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Tumor Necrosis Factor Decoy Receptors
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Tumor Necrosis Factor-alpha
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Dactinomycin