These include (upregulated) tumor-associated antigens like the BiTE and CAR target CD19 that are also found on healthy tissues [1, 112, 113], developmental or cancer-testis antigens whose expression is restricted to certain developmental stages or immune-excluded tissues [114, 115], as well as antigens accessible exclusively on tumor cells, including mutated neoantigens [116] and “liberated” antigens normally present in a bound, closed conformation. Here, CD19 is linked to cancer.