Activated human NK and CD8+ T cells express both TNF-related apoptosis-inducing ligand (TRAIL) and TRAIL receptors but are resistant to TRAIL-mediated cytotoxicity.
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.
Mirandola
Prisco
P
Department of Anatomy, Pharmacology and Forensic Medicine, University of Parma, Ospedale Maggiore, Via Gramsci, 14, I-43100 Parma, Italy.
Ponti
Cristina
C
Gobbi
Giuliana
G
Sponzilli
Ivonne
I
Vaccarezza
Mauro
M
Cocco
Lucio
L
Zauli
Giorgio
G
Secchiero
Paola
P
Manzoli
Francesco Antonio
FA
Vitale
Marco
M
D017209:Apoptosis / Q000187:drug effects; D051017:Apoptosis Regulatory Proteins; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein; D018414:CD8-Positive T-Lymphocytes / Q000166:cytology / Q000276:immunology* / Q000378:metabolism; D002478:Cells, Cultured; D003602:Cytotoxicity, Immunologic / Q000276:immunology*; D003609:Dactinomycin / Q000494:pharmacology; D005434:Flow Cytometry; D058851:GPI-Linked Proteins; D006801:Humans; D007376:Interleukin-2 / Q000494:pharmacology; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism; D007694:Killer Cells, Natural / Q000166:cytology / Q000187:drug effects / Q000276:immunology* / Q000378:metabolism; D008213:Lymphocyte Activation; D008562:Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D053220:Receptors, TNF-Related Apoptosis-Inducing Ligand; D018124:Receptors, Tumor Necrosis Factor / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D053320:Receptors, Tumor Necrosis Factor, Member 10c; D053221:TNF-Related Apoptosis-Inducing Ligand; D014158:Transcription, Genetic / Q000187:drug effects; D053319:Tumor Necrosis Factor Decoy Receptors; D014409:Tumor Necrosis Factor-alpha / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology
D051017:Apoptosis Regulatory Proteins; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein; C506386:CFLAR protein, human; D058851:GPI-Linked Proteins; D007376:Interleukin-2; D047908:Intracellular Signaling Peptides and Proteins; D008562:Membrane Glycoproteins; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D053220:Receptors, TNF-Related Apoptosis-Inducing Ligand; D018124:Receptors, Tumor Necrosis Factor; D053320:Receptors, Tumor Necrosis Factor, Member 10c; D053221:TNF-Related Apoptosis-Inducing Ligand; C105190:TNFRSF10A protein, human; C505639:TNFRSF10B protein, human; C108661:TNFRSF10C protein, human; C505653:TNFSF10 protein, human; D053319:Tumor Necrosis Factor Decoy Receptors; D014409:Tumor Necrosis Factor-alpha; D003609:Dactinomycin