RecruitingPhase 1Drug trialAutologous CD22 CAR T Cells Following Commercial CD19 CAR T Cells in B Cell MalignanciesThe primary purpose of this study is to determine safety, feasibility, and the Maximum Tolerated Dose (MTD)/Recommended Phase 2 Dose (RP2D) of CD22 Chimeric Antigen Receptor T-Cell Therapy (CART) cells when administered 28 to 42 days after an infusion of a commercial CAR called Tisagenlecleucel, to children and young adults with relapsed or refractory B-cell leukemia.