When Porter and colleagues infused a low dose (1.5 × 10 [5] cells per kilogram of body weight) of autologous anti-CD19 CAR-T cells in a patient with CLL, these cells expanded over 3 weeks to a level that was more than 1,000 times as high as the initial engraftment level in vivo. This evidence concerns the gene CD19 and B-cell chronic lymphocytic leukemia.