Fas ligand exerts its pro‐inflammatory effects via neutrophil recruitment but not activation

Abstract

Fas ligand (FasL) expression induces apoptosis of activated T cells and has been suggested as a strategy to inhibit graft rejection. Unfortunately, the use of FasL to confer 'immune privilege' in this setting has been hampered by the finding that it may also provoke a destructive granulocytic response. While the Fas/FasL-mediated apoptotic pathways are well defined, the pro-inflammatory effects of FasL are poorly understood. Our aim in this study was to define in vitro the biological effects of FasL on neutrophil recruitment and activation. DAP-3 cells expressing human FasL on the cell membrane (mFasL) potently induced apoptosis in human neutrophils and in activated T lymphocytes. Recombinant human soluble FasL (sFasL), by contrast, was a very weak inducer of apoptosis, even at high concentrations. This latter observation suggests that cleavage of mFasL by naturally occurring matrix metalloproteinases may serve to down-regulate FasL activity in vivo. However, in the presence of a cross-linking antibody, the efficiency of apoptosis-induction by sFasL was greatly increased, suggesting that the lesser pro-apoptotic potency of sFasL reflects an inability to induce trimerization of the Fas receptor. With regard to pro-inflammatory effects, we found that sFasL is a potent neutrophil chemoattractant and, given that it induces little apoptosis, the dominance of sFasL over mFasL may mean that graft-infiltrating neutrophils will survive to mediate inflammation. Neither sFasL nor mFasL produced neutrophil activation as assessed by chemiluminescence assay. This suggests that neutrophils recruited to an inflammatory site by FasL will be activated by mechanisms other than Fas-FasL signalling.

Cell Death Mechanisms Induced by Cytotoxic Lymphocytes

“…In addition, apoptosis is induced when soluble FasL forms tetramers or highly arranged structures (111). Fas/FasL pathway plays an important role in graft rejection (112), where soluble FasL can be chemotactic to neutrophils, during the acute rejection of a graft transplant (113).…”

Blocking Fas Ligand on Leukocytes Attenuates Kidney Ischemia-Reperfusion Injury

“…5 Fas is known to be involved in various forms of renal injury such as IRI 6 and tubular injury in glomerulonephritis. 7,8 FasL is also believed to have a role in inflammation through recruitment of inflammatory cells, 9,10 and induction of cytokine production. 11 Previous studies have demonstrated diverse results regarding FasL effects on various inflammatory processes, [12][13][14][15] which may be related to the pleiotropic effects of FasL and expressing cell types.…”

Toll-Like Receptor 3 Signaling Induces Chronic Pancreatitis through the Fas/Fas Ligand-Mediated Cytotoxicity

“…Soluble FasL can induce apoptosis in a hexameric form (Holler et al 2003). In the present study, the soluble FasLmediated cytotoxicity in MRL/S-1 cells treated with poly I:C was examined using synthetic His-fusion FasL in the presence of Anti-His 6 to make a aggregate form according to the method previously described (Dupont and Warrens 2007). His-fusion FasL was prepared in a cell-free protein synthesis system using wheat germ ribosomal RNA to avoid a risk of contamination with LPS, which induces TLR4-mediated signaling.…”

“…All assays were performed in triplicate for each experiment. Cytotoxicity inducing activity of synthetic His-fusion FasL (10 ng/ml) were also measured by the MTT assay in the presence of mouse monoclonal antibody for the detection of His 6 -tagged recombinant proteins (Anti-His 6 ) (Roche), which makes a aggregate form of His-fusion FasL to be efficient in the induction of the Fas/FasL-mediated cytotoxicity as indicated (Dupont and Warrens 2007).…”