Flow cytometry analysis of expression of Fas on COS cells transfected with Fas cDNAs.

COS cells were transfected with either the Fas cDNA, FasExo,6Del cDNA, or FasExo4,6Del cDNA and individual colonies were isolated. Single-cell suspensions were stained with either fluorescein isothiocyanate (FITC)–conjugated IgG1 isotype control mAb or FITC-conjugated anti-Fas mAb. Cytoplasmic staining was carried out by fixation of the cells with 0.5% paraformaldehyde and permeabilization with 0.1% Triton X-100 to allow entry of the antibody. Panels on the left represent surface staining; panels on the right represent cytoplasmic staining. The representative histograms show the specific binding (anti-Fas) and nonspecific binding (IgG1) as indicated.