To control the specificity of CD40-mediated and caspase-8–dependent cell death in an in vitro assay with CD8+ T cells, human EJ138 bladder carcinoma cells, and A704 renal adenocarcinoma cells, we generated CD40−/− and caspase-8−/− variants of both lines (Fig. 6, A and B). Here, CD40 is linked to papillary renal cell carcinoma.