Differential activation of the death receptor pathway in human target cells induced by cytotoxic T lymphocytes showing different kinetics of killing.
OBJECTIVE
Cytotoxic T lymphocytes (CTL) may use two effector mechanisms to kill their target cells: perforin (PFN) and granzyme B (GrB)-dependent granule-mediated cell death and death receptor-mediated cell death. Controversy exists whether, in addition to PFN/GrB-mediated apoptosis, death receptor-induced apoptosis contributes to the elimination of human tumor cells by CTL.


METHODS
Since the two CTL-mediated effector mechanisms differ in time required to eliminate target cells, lysis of target cells was analyzed using CTL clones with slow and rapid kinetics of killing derived from a patient with chronic myeloid leukemia. To determine the involvement of the death receptor pathway, a retroviral construct encoding the antiapoptotic gene FLICE inhibitory protein (FLIP) was introduced into these target cells.


RESULTS
A CTL clone capable of killing 50% of the target cells within 2 hours of incubation primarily acted by release of PFN and GrB. In contrast, two CTL clones showing slower target cell killing kinetics partially used the death receptor pathway (approximately 30% inhibition by FLIP).


CONCLUSIONS
We demonstrated that the death receptor pathway contributes to T-cell-mediated cell death if not all target cells are destroyed by release of PFN and GrB.
Department of Hematology, Leiden University Medical Center, P.O. Box 9600, 2300 RC Leiden, The Netherlands. j.f.vries@lumc.nl
Jeltje F
JF
de Vries
Peter A
PA
von dem Borne
Simone A P
SA
van Luxemburg-Heijs
Mirjam H M
MH
Heemskerk
Roel
R
Willemze
J H Frederik
JH
Falkenburg
Renèe M Y
RM
Barge
D017209:Apoptosis / Q000235:genetics / Q000276:immunology*; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein / Q000235:genetics / Q000276:immunology; D053181:Caspase 8 / Q000276:immunology; D061945:Caspase Inhibitors; D016923:Cell Death / Q000235:genetics / Q000276:immunology; D053804:Granzymes / Q000276:immunology*; D006801:Humans; D007111:Immunity, Cellular / Q000235:genetics / Q000276:immunology; D015464:Leukemia, Myelogenous, Chronic, BCR-ABL Positive / Q000235:genetics / Q000276:immunology*; D054353:Perforin / Q000276:immunology*; D018124:Receptors, Tumor Necrosis Factor / Q000276:immunology; D012190:Retroviridae; D013601:T-Lymphocytes / Q000276:immunology*; D013997:Time Factors; D014161:Transduction, Genetic; D014407:Tumor Cells, Cultured
D053446:CASP8 and FADD-Like Apoptosis Regulating Protein; D061945:Caspase Inhibitors; D018124:Receptors, Tumor Necrosis Factor; D054353:Perforin; D053804:Granzymes; C505530:CASP8 protein, human; D053181:Caspase 8