Flow cytometry analysis of the Fas ligand expression of activated lymph node T-cells

Modulation of TNF-α activity in tumor PC cells using anti-CD45 and anti-CD95 monoclonal antibodies

TNF-alpha is a pleiotropic cytokine produced by activated T-cytotoxic lymphocytes and NK cells that is involved in signal transduction after interacting with the appropriate cell surface receptors. The modulation of signals by TNF-alpha receptor super-family is involved in the regulation of cell activation, proliferation, differentiation and control of the cell survival including cell death by apoptosis and necrosis. We have monitored the kinetics of apoptosis/necrosis on PC cells, after TNF-alpha exposure of pre-treated cells to anti-CD95 and anti-CD45 monoclonal antibodies. The results showed that in comparison with untreated cells, TNF-alpha, after 6-24 h of incubation significantly increased apoptosis and necrosis in PC cells. These effects were significantly different in comparison to both untreated cells and cells pre-treated with anti-CD45 monoclonal antibodies. However, TNF-alpha on PC cells pre-treated with anti-CD95 monoclonal antibody significantly decreased apoptotic and necrotic form of cell death. We concluded that anti-CD45 and CD95 monoclonal antibodies modulates the effect of TNF-alpha on this cell line in vitro, and that these molecules participate in TNF-alpha cytotoxic response.

Expression of mutant non-cleavable Fas ligand on retrovirus packaging cells causes apoptosis of immunocompetent cells and improves prodrug activation gene therapy in a malignant glioma model

Recombinant retroviruses (RV) have been widely used as vectors for clinical gene therapy of malignant brain tumors. Because of the very limited stability of these vectors in vivo, RV producing cells (VPC) are routinely used for intratumoral RV release. The host immune system, however, recognizes the intratumorally grafted allogeneic or xenogeneic VPC, and mounts an immune response against them. Humoral and cellular immune responses eventually result in reduction of VPC numbers and in limited success of RV mediated gene therapy approaches. This study presents a non-pharmacological and spatially limited approach for protection of VPC grafted in the CNS against destruction by host immune responses. Murine fibroblast-derived VPC expressing herpes-simplex-virus type I thymidine kinase (HSV-tk) were genetically modified to co-express a human Fas ligand (CD95L) deletion mutant (DeltaFasL) resistant to enzymatic cleavage and shedding. Direct interactions between Fas (CD95) on lymphocytes and DeltaFasL on VPC upon cell-cell contact rapidly caused apoptosis in lymphocytes. In addition, cultured malignant brain tumor cells (U87, LN18, LN229) transduced with DeltaFasL-RV were rendered apoptotic by Fas/DeltaFasL interaction. DeltaFasL-expressing VPC grafted in a 9L rat brain tumor model survived in significantly higher numbers compared with control VPC, and did not cause an increase in neutrophil infiltration of tumors. Gene therapy of tumor bearing animals grafted with the modified DeltaFasL-VPC and given the prodrug Ganciclovir resulted in significantly increased survival rates compared to treatment with control VPC and Ganciclovir. In conclusion, prolonged intratumoral presence of DeltaFasL-VPC seems to be a direct consequence of the expression of the membrane-bound mutant FasL, and may result in increased total RV output and improved tumor transduction with RV.

Expression of Fas (CD95) and Fas ligand on peripheral blood mononuclear cells in critical illness and association with multiorgan dysfunction severity and survival

OBJECTIVE

This was an exploratory study with three goals: a) to quantify the expression of the apoptotic receptor Fas and its ligand (FasL) on peripheral blood mononuclear cells (PBMCs) in patients with, or at risk for, multiple organ dysfunction syndrome (MODS); b) to compare this expression with the respective expression in matched controls; and c) to explore the association with MODS severity and survival.

DESIGN

Repeated-measures correlational and cross-sectional design.

SETTING

The surgical, medical, and the trauma/burn intensive care unit of an academic institution.

PATIENTS

Thirty-five adult, critically ill patients meeting the diagnostic criteria for systemic inflammatory response syndrome (SIRS) with MODS, or at risk for MODS, were followed for 14 days. Thirty-five non-SIRS controls matched with patients for age, gender, and race comprised the control group.

INTERVENTIONS

Peripheral blood sampling every 48 hrs.

MEASUREMENTS/MAIN RESULTS

T cells were considerably depleted in SIRS/MODS patients (p <.001), and Fas and FasL expression on PBMCs (flow cytometric analysis) was elevated significantly compared with controls (p <.001). In contrast to controls, non-T cells were the major sources of Fas and FasL in SIRS/MODS patients (p <.01). Expression of Fas and FasL exhibited a bimodal correlation with severity (p <.03). High severity patients demonstrated increasing Fas and FasL expression with increasing severity in contrast to declining expression in moderately severe patients. Fas and FasL measurements were significantly and positively associated with the likelihood of survival (p <.05).

CONCLUSIONS

Dysregulation in the expression of apoptotic receptors Fas and FasL, at least in PBMCs, may be involved in the pathophysiology of SIRS, the related lymphocytopenia, and the onset of MODS and the related morbidity and mortality rates.