Chimeric antigen receptor (CAR) T cells targeting CD19 will be evaluated for safety and efficacy in patients with B cell lymphoma or leukemia. The CAR consists of a CD19 targeting antibody scFv with three intracellular signaling domains derived from CD3 zeta, CD28 and 4-1BB. Autologous T cells will be gene engineered with the CAR gene using a retrovirus vector. Prior to T cell infusion, the patients will be subjected to preconditioning treatment. After T cell infusion, the patients will be evaluated for 24 months for adverse reactions, persistence of CAR T cells and efficacy.

Inclusion Criteria:

• Relapsed or refractory CD19+ B-cell lymphoma or leukemia.
• Measurable disease.
• Performance status ECOG 0-2.
• >18 years old.
• Fertile females/males must consent to use contraceptives during participation of the trial.
• Signed informed consent.

Exclusion Criteria:

• Any significant medical or psychiatric illness that would prevent the patient from giving informed consent or from following the study procedures.
• Patients with primary CNS lymphoma.
• Known human immunodeficiency virus (HIV) infection.
• Active and/or severe infection (e.g. tuberculosis, sepsis and opportunistic infections, active hepatitis B virus (HBV) or active hepatitis C virus (HCV) infection).
• Other serious underlying medical conditions, which, in the Investigator's judgment, could impair the ability of the patient.
• Treatment with an investigational product within 30 days prior to enrollment, or at least 5 half lives of that drug, which is longest.
• Patients that do not consent to that tissue and blood samples are stored in a biobank.
• Pregnancy