Effect of sFasL on cell targeting of the FasL-containing chimeras.

<p>Panel A : Schematic description of the experimental model used. The chimera is enriched at the surface of the CD32-expressing L-cells via its HLA targeting module and an anti-HLA monoclonal antibody. Panel B: murine Fas (continuous line), human CD32 (dashed line) and IgG1 isotype-matched control (shaded histogram) staining of the CD32+ L-cell transfectant. Living cells were gated on the basis of the morphological parameters. Panel C : Fas sensitivity of the CD32+ L-cell transfectant to the indicated concentrations of the anti-Fas JO-2 antibody (circles), the HLA-pfFasL chimera expressed alone (triangle) or in the presence of 25% of the sFasL plasmid (squares), in the MTT viability assay. Panel D : The CD32+ L-cells were incubated with the HLA-pfFasL chimera produced in the presence (black bars) or in the absence (white bars) of 25% of the sFasL plasmid, together with the indicated irrelevant IgG1 isotype-matched, anti-beta-2 microglobulin or anti-Flag antibodies. The concentrations of the chimera that triggered 15% of cell death and were at 15 and 0.3 ng/ml in the absence and presence of sFasL, as estimated using the ELISA specific for the Flag-tagged FasL. Cytotoxicity was measured with the propidium iodide assay and normalized to the effect of the chimera in the absence of antibody. Are presented the mean +/- sd of three independent experiments. Panel E: reversal in the presence of the blocking anti-FasL and anti-CD32 antibodies, of the cytotoxic effect of the immune complexes between the anti-Flag antibody and HLA-pfFasL co-expressed with sFasL. Are presented the mean +/- sd of three independent experiments. ns : non significant ; ** p≤0.02.