Examination of the Sensitivity of T Cells to Fas Ligation

O'Flaherty, E; Ali, Simi; Pettit, Stephen; Kirby, John A.

doi:10.1097/00007890-199810270-00017

Cited by 25 publications

(15 citation statements)

References 37 publications

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“…Although activated T cells up-regulate Fas receptor (CD95) on their surfaces from the first day after activation, they become sensitive to proapoptotic triggering ligand (FasL) only at days 3-6 after stimulation (34 -36). The initial resistance to FasL-induced apoptosis is believed to be related to anti-apoptotic signals that emerge in the course of T cell stimulation (35,36). One critical anti-apoptotic protein appears to be the FLICE inhibitory protein, cFLIP (37,38,(41)(42)(43)(44).…”

Section: Discussionmentioning

confidence: 99%

CTLA-4 · FasL Induces Early Apoptosis of Activated T Cells by Interfering with Anti-Apoptotic Signals

Orbach

Rachmilewitz

Parnas

et al. 2007

The Journal of Immunology

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The fusion protein CTLA-4 · FasL, a paradigmatic “trans signal converter protein”, can attach to APC surfaces and in effect convert B7-activating costimulator signals into inhibitory Fas receptor-generated signals. The present study investigates CTLA-4 · FasL’s mechanism of action. A combination of p27kip and proliferating cell nuclear Ag Western blot and propidium iodide flow cytometric analysis showed no CTLA-4 · FasL effect on cell cycle entry and progression, pointing away from the kind of classical anergy associated with CTLA-4 · Ig. Significantly, CTLA-4 · FasL elicited apoptosis (as detected by annexin-V/propidium iodide costaining) as early as 24 h after T cell activation, suggesting that some coordinate signaling might be capacitating the Fas receptor. Significantly, CTLA-4 · FasL, but not CTLA-4 · Ig, anti-Fas mAb, or the two in combination, abrogated the usual increase in expression of the anti-apototic protein, cFLIP. Furthermore, activation of caspases 8 and 3 were not affected by CTLA-4 · FasL. These findings suggest a model for CTLA-4 · FasL action wherein there is coordinate triggering of a death receptor and suppression of a proapoptotic protein.

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Section: Discussionmentioning

confidence: 99%

CTLA-4 · FasL Induces Early Apoptosis of Activated T Cells by Interfering with Anti-Apoptotic Signals

Orbach

Rachmilewitz

Parnas

et al. 2007

The Journal of Immunology

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“…This result is in good agreement with the previous observation that antiallogeneic lymphocytes challenged with the relevant target cell showed a reduction in proliferation of approximately 35% when they were preincubated with anti-Fas antibody. 38 …”

Section: Fas-transduced T Lymphocytes Are Able To Mount a Specific Anmentioning

confidence: 99%

A Fas-based suicide switch in human T cells for the treatment of graft-versus-host disease

Thomis

Marktel

Bonini

et al. 2001

Blood

177

124

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Graft-versus-host disease (GVHD) is a major complication of allogeneic bone marrow transplantation. One strategy to treat GVHD is to equip donor T cells with a conditional suicide mechanism that can be triggered when GVHD occurs. The herpes simplex virus thymidine kinase (HSV-tk)/ganciclovir system used clinically has several limitations, including immunogenicity and cell cycle dependence. An alternative switch based on chemically inducible apoptosis was designed and evaluated. A chimeric human protein was expressed comprising an extracellular marker (⌬LNGFR), the Fas intracellular domain, and 2 copies of an FK506-binding protein (FKBP). Primary human T lymphocytes retrovirally transduced with this construct could be purified to homogeneity using immunomagnetic beads. Genetic integrity of the construct was ensured by redesigning repetitive sequences. Transduced T cells behaved indistinguishably from untransduced cells, retaining the ability to mount a specific antiallogeneic immune response. However, they rapidly underwent apoptosis with the addition of subnanomolar concentrations of AP1903, a bivalent "dimerizer" drug that binds FKBP and induces Fas cross-linking. A single 2-hour treatment eliminated approximately 80% of T cells, and multiple exposures induced further apoptosis. T cells were eliminated regardless of their proliferation state, suggesting that the AP1903/ Fas system, which contains only human components, is a promising alternative to HSV-tk for treating GVHD. IntroductionIn allogeneic bone marrow transplantation (BMT), the delayed infusion of donor lymphocytes plays a central therapeutic role in the control of disease relapse (graft-versus-leukemia effect [GVL]) 1 and in the induction of immune reconstitution, 2,3 the latter especially in the subset of T-depleted matched transplants and in the context of partially mismatched transplants. 4 However, graft-versushost-disease (GVHD) represents a frequent and often lethal complication of delayed lymphocyte infusions. 1 Managing the threat of GVHD while maximizing the beneficial GVL effect would broaden the scope and usefulness of allogeneic BMT procedures.We and others have previously demonstrated that ex vivo genetic manipulation of donor lymphocytes to insert a conditional, drug-inducible suicide gene provides a means for the specific elimination of donor T cells with the onset of GVHD while maximizing the therapeutic benefit of the GVL effect. 2,5,6 Although a number of suicide genes have been proposed, 7,8 the herpes simplex virus thymidine kinase (HSV-tk)/ganciclovir (GCV)-based suicide strategy appears to be the most effective and specific and has been widely adopted. 9,10 Cells are engineered to express HSV-tk; the addition of ganciclovir leads to cell death through tk-catalyzed metabolism of the drug to a lethal product. In the current clinical trial, 6 HSV-tk-engineered-donor T cells demonstrated an effective antileukemic effect, and GVHD could be successfully treated through GCV administration. 2,11 Despite this demonstration of efficacy, ...

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“…It has been shown that T cells only acquire sensitivity to Fas‐mediated apoptosis some days after antigen‐specific activation 14,15 . The current study was designed to investigate the molecular events that regulate apoptosis by application of an MLR system, which allows the processes of primary T‐cell activation to be modelled in vitro .…”

Section: Introductionmentioning

confidence: 99%

Regulation of T‐cell apoptosis: a mixed lymphocyte reaction model

et al. 2000

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SUMMARYDespite the capacity for antigen-speci®c activation and rapid clonal expansion, homeostatic mechanisms ensure that the mature immune system contains a relatively stable number of T cells. In recent years, it has become apparent that this stability is a consequence of apoptotic death of most of the speci®c T cells generated during an immune response. Clearly this process must be tightly regulated in order to retain suf®cient T-cell progeny to mediate an effective response, whilst allowing the rapid deletion of these cells at the end of the response to prevent lymphadenopathy and cross-reactive autoimmunity. In this study, the factors that regulate the sensitivity of T cells to apoptosis were investigated in vitro after the induction of primary T-cell activation within a mixed lymphocyte reaction (MLR). It was found that activated T cells rapidly acquire the expression of both Fas and Fas ligand (FasL) on their surface and contain high levels of the precursor form of the pro-apoptotic enzyme, caspase 8 (FLICE). However, these T cells were resistant for up to 5 days to apoptosis following the stimulation of Fas; a maximal apoptotic response was observed after 7 days. This time point coincided with a marked reduction in expression of the FLICE inhibitory protein (FLIP) and maximal activity of caspase 8. At time points beyond day 7, the number of viable cells in the MLR decreased further despite a reduction in the expression of FasL. However, the expression of interleukin-2 (IL-2) at these late time points was low, resulting in a decrease in expression of the anti-apoptotic protein Bcl-2. This can produce apoptosis by allowing leakage of cytochrome-c from mitochondria resulting in direct activation of the caspase cascade. In this study, it is shown that T cells are resistant to apoptosis for the ®rst 5 days after activation as a consequence of insensitivity of the Fas pathway and the presence of intracellular Bcl-2. After between 5 and 7 days, the cells become sensitive to Fas-mediated apoptosis while retaining Bcl-2 expression. At later time points, Fas ligation is reduced but the cells respond to a decreased availability of IL-2 by reducing Bcl-2 expression; this encourages further apoptosis by allowing the direct activation of caspase enzymes.

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Examination of the Sensitivity of T Cells to Fas Ligation

Cited by 25 publications

References 37 publications

CTLA-4 · FasL Induces Early Apoptosis of Activated T Cells by Interfering with Anti-Apoptotic Signals

CTLA-4 · FasL Induces Early Apoptosis of Activated T Cells by Interfering with Anti-Apoptotic Signals

A Fas-based suicide switch in human T cells for the treatment of graft-versus-host disease

Regulation of T‐cell apoptosis: a mixed lymphocyte reaction model

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