Fig. 5.

Cell death response to Fas triggering of control HUT78 cells and hybrid cell lines obtained by fusing HUT78 cells with Fas-resistant T cells from four Fas-resistant GD and three Fas-resistant HT patients. Hybrid cells are resistant to Fas-induced cell death, whereas control HUT78 cells are not. Cells were treated with the anti-Fas MoAb and cell death was evaluated after 12 h by staining cells with annexin V and propidium iodide. The FACS profiles show staining with annexin V of propidium iodide-negative cells from the untreated (grey lines) and anti-Fas MoAb treated (black lines) cells. The numbers indicate the proportion of annexin V⁺ cells in the anti-Fas MoAb-treated sample less the proportion of annexin V⁺ cells in the untreated sample. Similar results were obtained when propidium iodide-positive cells were also included to detect both early and late apoptotic cells. Fas-sensitive hybridomas could not be raised, as they were killed by the selection media (containing anti-Fas MoAb) during the early phases of hybridoma production.