T cell receptor‐induced Fas ligand expression in cytotoxic T lymphocyte clones is blocked by protein tyrosine kinase inhibitors and cyclosporin A

Abstract

Fas/APO-1 is a member of the tumor necrosis factor receptor family of proteins that induces apoptosis when cross-linked with monoclonal antibody (mAb) or with its physiological ligand. Recently, both a perforin-based and a Fas-based mechanism have been proposed to account for T cell-mediated cytotoxicity. In the present study we used a murine CD8+ cytotoxic T lymphocyte (CTL) clone (KB5 C20) specific for H-2Kb and a T cell receptor (TcR)-negative variant of the same clone (2005-D4) to test (i) whether the same cell can exert both cytotoxic effector mechanisms and (ii) the role of TcR engagement in the induction of Fas-based cytotoxicity. We demonstrate that both the TcR+ and TcR- clones were able to express the Fas ligand after stimulation with phorbol 12-myristate 13-acetate (PMA)/ionomycin, and that TcR engagement of the KB5.C20 clone by means of antigen-bearing cells or of its anticlonotypic mAb (Désiré-1), which leads to Ca(2+)-dependent, presumably perforin-based, cytotoxicity, was also able to induce Fas-based cytotoxicity. In addition, using inhibitors we investigated the signal transduction pathway(s) involved in the induction of Fas-based cytotoxicity and expression of the Fas ligand mRNA in the CTL clones. The involvement of src-like protein tyrosine kinases (PTK) in Fas ligand induction through TcR engagement, was strongly suggested by inhibition with the src-like PTK inhibitor herbimycin A. Inhibition of Fas ligand induction by genistein, a more general TPK inhibitor, even upon stimulation by PMA plus ionomycin, suggested the possible involvement of PTK activities downstream of protein kinase C (PKC) in Fas ligand induction in CTL. Finally, the implication of the Ca2+/calmodulin-dependent protein phosphatase calcineurin in Fas ligand induction was demonstrated by the partial inhibition of Fas ligand induction with cyclosporin A. Thus, in CTL clones, Fas ligand expression is inducible by TcR engagement through a pathway similar to that involved in expression of some lymphokine genes.

Distinct requirements for activation-induced cell surface expression of preformed Fas/CD95 ligand and cytolytic granule markers in T cells

“…This indicates that degranulation of preformed FasL occurs in response to both TCR stimulation and to stimulation with PMA. In agreement with this finding we observed that anti-CD3 stimulation induced FasL transcription, which was blocked by CsA 13,14 whereas PMA failed to do so (Figure 2d). …”

Increased soluble Fas-ligand in sera of bone marrow transplant recipients with acute graft-versus-host disease

“…The former is likely, because it has been shown that the expression of FasL transcripts is induced by T cell receptor engagement. 14 In addition, an increase in the percentage of CD8 + cells which express FasL in patients with aGVHD has been demonstrated. 15 The relationship between the Fas/FasL system and the development of aGVHD is complex.…”

Using death to one's advantage: HIV modulation of apoptosis

“…[136][137][138] Both of these types of kinases are important in T cell activation. [136][137][138][139] Consistent with this observation, Fas-L is expressed following activation of the TCR leading to the phosphorylation of these kinases and expression is inhibited by cell treatment with immunosuppressive drugs. 139 Ras signaling has also been implicated in tyrosine kinase activation and hence both the Ras and Lck pathways may contribute to the up-regulation of Fas-L transcription.…”

“…[136][137][138][139] Consistent with this observation, Fas-L is expressed following activation of the TCR leading to the phosphorylation of these kinases and expression is inhibited by cell treatment with immunosuppressive drugs. 139 Ras signaling has also been implicated in tyrosine kinase activation and hence both the Ras and Lck pathways may contribute to the up-regulation of Fas-L transcription. 140 Therefore, HIV infection may activate tyrosine kinases (via Nef) that converge in a common activation pathway leading to Fas/Fas-L interaction and the induction of apoptosis.…”