To evaluate the ability of anti-CD19 CAR T cells to kill CD19+ tumor cells in vivo, we next implanted balb/c mice with the same preparation of 4T1-mCD19 breast cancer cells and allowed the tumors to reach ~50 mm3 in size before infusing the mice intravenously with either saline or anti-CD19 CAR T cells. The gene discussed is CD19; the disease is breast cancer.