CXCL13 and neoplasm: During tumor targeting, CAR T cells undergo strong stimulation that can trigger activation‐induced cell death (AICD), which contributes to their reduced persistence.[37, 38] To assess the effect of AICD, we co‐cultured CAR T cells with tumor cells at various ratios and observed that CXCL13 CAR T cells consistently showed reduced apoptosis (Figure 4e).