This is a single-centre, single-arm and open-label study to investigate the safety and efficacy of anti CD19 CAR NK cells in patients with relapsed refractory B cell lymphoma.

Inclusion Criteria:

1. CD19 (+) B cell lymphoma confirmed by pathological immunohistochemistry or flow cytometry
2. Previously accepted ≥ first-line regimen chemotherapy
3. Unconditional acceptance of hematopoietic stem cell transplantation or recurrence after hematopoietic stem cell transplantation
4. Over 18 years old and under 70 years old
5. The expected survival period is more than 3 months.
6. ECOG≤2
7. Important organ function is satisfied: cardiac ultrasound indicates cardiac ejection fraction ≥50%, no abnormal electrocardiogram; blood oxygen saturation ≥90%; creatinine clearance ≥40 mL/min; ALT and AST≤3 times normal range, Total bilirubin ≤ 2.0 mg / dL;
8. Blood routine: Hgb≥80 g/L, ANC≥1×109/L, PLT≥50×109/L;
9. The pregnancy test for women of childbearing age must be negative; both men and women must agree to use effective contraception during the treatment period and for the following 1 year.
10. Measurable target lesion

Exclusion Criteria:

1. Patients with extramedullary relapse

2. Burkitt's lymphoma/leukemia

3. Previously received gene product treatment, anti-CD19/anti-CD3 treatment, or any anti-CD19 treatment;

4. Liver and kidney function:

   • Total bilirubin > 2 x ULN (Gilbert Syndrome > 3 x ULN)
   • Aspartate aminotransferase (AST) and alanine aminotransferase (ALT) > 3 × ULN
   • Serum creatinine clearance >60 mL/min

5. Serological examination:

   • Absolute neutrophil count (ANC) <0.75x109/L
   • Platelet count (PLT) <50x109/L

6. Active hepatitis B (HBV-DNA > 1000 copies / mL), hepatitis C, or uncontrolled infection

7. GVHD ≥ 2 or anti-GVHD treatment

8. IM19 CAR NK cells received allogeneic cell therapy within 6 weeks before infusion, such as donor lymphocyte infusion;

9. Subject received the most recent treatment (release, chemotherapy, or other) less than 4 weeks

10. Active CNS disease (tumor cells in CSF, but < 5 WBCs/mL can be included);

11. Intracranial hypertension or unconsciousness; respiratory failure; diffuse vascular internal coagulation

12. Creatinine > 1.5 times normal upper limit or ALT / AST > 3 times normal upper limit or bilirubin > 2 times normal upper limit

13. New York Heart Association (NYHA) graded above or above

14. Uncontrollable diabetes

15. Suffering from other uncontrolled diseases, the researchers believe that it is not suitable for joining

16. Any situation that the investigator believes may increase the risk of the subject or interfere with the test results