This study aims to evaluate the safety and clinical activity of CD19 Chimeric Antigen Receptor (CAR) redirected autologous T-cells in treating patients with recurrent or refractory CD19 positive B cell ccute lymphoblastic leukemia,and dynamically observe the changes of CAR-T in patients and the residual tumor.

In this single-center, open-label, single-arm, prospective clinical trial, a total of 20 recurrent or refractory CD19+ B cell acute lymphoblastic leukemia patients will be enrolled.After recruiting eligible patients,autologous peripheral blood mononuclear cells(PBMCs) will be purified from whole blood.The CD3+ T cells were subsequently selected and re-stimulated by anti-CD3 and anti-CD28 monoclonal antibodies.T cells will be transduced with lentiviral vector for the generation of the CD19 CART cell and administered by i.v. injection.The purpose of current study is to determine the safety and clinical efficacy of CD19 CAR T cells therapy in patients with recurrent or refractory CD19+ ALL.

Inclusion Criteria:

• Recurrent or refractory B cell derived acute lymphoblastic leukemia (ALL)
• Patients who have failed at least one line of a standard treatment without effective treatment measures at present
• CD19 expression on the surface of B-ALL cells must be detected
• KPS>80
• Life expectancy >3 months
• Patients must have adequate cardiac function (no electrocardiogram with obvious abnormality, LVEF≥50%),adequate pulmonary function as indicated by room air oxygen saturation of > 90%, and adequate renal function (Cr≤2.5 times of the normal range)
• The alanine aminotransferase (ALT) and the aspartate aminotransferase (AST)≤ 3 times of the normal range, and the total bilirubin (TBIL)≤2.0mg/dl(34.2umol/L)
• Hemoglobin(Hgb)≥80g/L
• Without contraindication of apheresis and cell isolation
• Patients and their families volunteer to participate in the research with signed written informed consent

Exclusion Criteria:

.Other concurrent severe and/or uncontrolled medical conditions: patients with another primary malignant disease; another severe and/or life-threatening medical disease.

• Evidence of uncontrolled current serious active infection
• HIV/HBV/HCV infection
• Pregnancy and nursing females
• Systemic glucocorticoid therapy within one week