A Study to Assess CD19-targeted Immunotherapy T Cells in Patients With Relapsed or Refractory CD19+ B Cell Leukemia

In the conventional treatment options, B cell leukemia could be treated with chemotherapy drugs or HSCT. But chemotherapy could barely cured leukemia. And HSCT is often limited by lacking of HLA-matched donors, even if those patients who received HSCT still could be relapsed. And now, chimeric antigen receptor modified T cell infusion maybe an effective treatment to solve these problems. The investigators use a 2nd CAR- T with the optimized hinge and transmembrane domain to treat patients with relapsed or refractory B cell leukemia, including relapsed cases after HSCT. The purpose of this study is to assess the safety and efficacy of this 2nd CAR-T cells. At the same time, evaluating the possible and clinical responses of using donor-derived T cells engineered CAR-T cells. Detailed Description: This study is being conducted to assess anti-CD19-CAR-T cells safety and efficacy in treating patients with B cell leukemia. The investigators constructed a 2nd CAR, CD19 as target protein, 4-1BB as co-stimulator. And optimized the spatial conformation by a suitable hinge \& transmembrane domain sequences. The source of T cells for CAR-T is from two aspects, one is autologous, the other is donor-derived (only suitable for patients received HSCT before and relapsed). The infusion dose is (1-5)×106 CAR positive T cells/kg, and the specific cells numbers depend on the situation of individual CAR-T cells preparation.