Cell Therapy and Immunotherapy |
From the Department of Hematology, Leiden University Medical Center, Leiden, The Netherlands
Correspondence: Jeltje F. de Vries, MSc, Department of Hematology, Leiden University Medical Center, P.O. Box 9600, 2300 RC Leiden, The Netherlands. E-mail: j.f.vries{at}lumc.nl
Background and Objectives: 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.
Design and 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 (~30% inhibition by FLIP).
Interpretation and 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.
Key words: apoptosis, cytotoxic T lymphocyte, retroviral vector, Fas, FLIP, death receptor pathway.