The goal of this observation study is to test in relapsed or refractory acute lymphoblastic leukemia (R/R ALL) patients undergoing allogeneic hemopoietic stem-cell transplantation (allo-HSCT). The main question it aims to answer is:

• Effect of post-transplant blinatumomab treatment on immune reconstitution after transplantation.

Participants will undergo immune repertoire sequencing(IR-SEQ) before blinatumomab treatment, 6 months and 1 year after transplantation.

Researchers will compare patients who don't receive blinatumomab treatment after transplantation to see if TCR or BCR expression differs.

Inclusion Criteria:

1. Aged 16-65 years old
2. KPS score > 60 or ECOG score 0-2
3. diagnosed as B-ALL, a) disease status > CR1 at the time of transplantation; Patients beyond CR1 or induction failure could be free of minimal residual disease (MRD). b) any residual disease, defined as >0.01% leukemic cells by flow cytometry, BCR-ABL transcript ≥ 1 in 10000 by PCR, or high-risk genetic abnormality
4. neutrophil count ≥0.5×10^9/L and platelet count ≥20×10^9/L
5. creatinine clearance ≥30ml/min; Alanine aminotransferase/aspartate aminotransferase ≤5 times the upper detection limit; Total bilirubin ≤3 times the upper limit of detection
6. The first initiation of berintuzumab therapy was within 60-100 days after transplantation
7. without evidence of active acute graft-versus-host disease (aGvHD)

Exclusion Criteria:

1. With serious basic diseases of important organs, such as myocardial infarction, chronic cardiac insufficiency, decompensated liver dysfunction, renal dysfunction, gastrointestinal dysfunction, etc
2. With clinically uncontrolled active infection
3. Patients with central nervous system involvement before transplantation
4. Poor graft function (PGF) occurred after allo-HSCT
5. Patients with second allogeneic transplantation

Relapsed or refractory acute lymphoblastic leukemia (R/R ALL) patients undergoing allogeneic hemopoietic stem-cell transplantation (allo-HSCT).