To redirect the CD19-CAR T cells towards the ErbB2+ cancer cells, we used the CD19-4D5scFv fusion protein (#42) consisting of the extracellular CD19 domain and the herceptin-derived 4D5scFv binding domain linked to a his tag, as previously reported [18] (Figure 2A); the CD19-his tagged protein (#28) served as the control. Here, CD19 is linked to cancer.