Chimeric antigen receptor (CAR) T cells targeting CD20 will be evaluated for safety and efficacy in patients with CD20+ B cell lymphoma. The CAR consists of a CD20 targeting antibody scFv with two intracellular signaling domains derived from CD3 zeta and CD28. 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:

1. Relapsed or refractory CD20+ B-cell lymphoma.
2. Measurable disease.
3. Performance status ECOG 0-2.
4. Age:18-65.
5. Fertile females/males must consent to use contraceptives during participation of the trial.
6. Signed informed consent

Exclusion Criteria:

1. Any significant medical or psychiatric illness that would prevent the patient from giving informed consent or from following the study procedures.

2. Patients with primary CNS lymphoma.

3. Known human immunodeficiency virus (HIV) infection.

4. Active and/or severe infection (e.g. tuberculosis, sepsis and opportunistic infections, active hepatitis B virus (HBV) or active hepatitis C virus (HCV) infection).

5. Other serious underlying medical conditions, which, in the Investigator's judgment, could impair the ability of the patient.

6. Treatment with an investigational product within 30 days prior to enrollment, or at least 5 half lives of that drug, which is longest.

7. Patients that do not consent to that tissue and blood samples are stored in a biobank.

8. Pregnancy.

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