Cytotoxicity of HO-1 against Fas-positive and -negative target cells. (A) B-LCLs were established from the donor for HO-1 (Fas^+/+), the patient’s father (Fas^+/−), and the patient with Fas deficiency (Fas^−/−). Cells were stained with FITC-conjugated mouse anti-Fas MoAb (shaded histograms) or FITC-conjugated mouse IgG (open histograms). The fluorescence profiles were analyzed with a flow cytometer. (B) HO-1–induced lysis of DEK-CAN peptide-loaded (open columns) and unloaded (shaded columns) target cells was determined by⁵¹Cr release assays over 4 hours at E:T ratios of 10:1, 5:1, and 2.5:1.