CD19 and B-cell chronic lymphocytic leukemia: Especially, in a recent study by Melenhorst et al., they found that CD19-specific CAR T cells not only have anti-tumor capabilities against chronic lymphocytic leukemia but also showed persistency and signaling in CD19 CAR T cells that acted as living drugs in two patients with leukemia, a decade after initial treatment, at the expenseof B-cell aplasia due to on-target off-tumor toxicity [6].