SERPINB9 and neoplasm: To rule out if Fas expression is a major contributor to tumor cell death upon FasL ligation by CAR T cells, we pre-incubated 19–41BB CAR T cells with an anti-FasL antibody and loaded them on a TIMING chip with NALM6 or NALM6-PI9 cells and excess FasL antibody (Fig. 4A).