To investigate whether the addition of recombinant humanized anti-CD25 monoclonal antibody to the conventional EBV-T/NK LPD conditioning regimen can prevent acute and chronic GVHD after transplantation, improve the severity of GVHD and have a corresponding impact on other related post-transplant complications such as poor engraftment, thrombotic microvascular disease, early EBV reactivation and relapse.

Inclusion Criteria:

• Meet the diagnosis of EBV-T/NK lymphoproliferative disease (EBV-T/NK LPD) according to the ICC2022 diagnostic criteria
• Plan to undergo allogeneic hematopoietic stem cell transplantation (allo HSCT) in our hospital
• Age ≤ 18 years old
• Sign informed consent form
• Meet one of the following conditions (haploid donors must meet one of the above conditions, unrelated donors must meet two of the above conditions): ① donor age≥40 years old; ② The donor source is unrelated donor or haplotype related female or collateral donor (brother sisters, etc.) with ≥ 1 point mismatch; ③ CD3≥4 x 10 ^ 8/kg before transplantation; ④ The primary disease is in an HLH (hemophagocytic lymphohistiocytosis) flare or active disease phase; ⑤ ATG (or ATLG (1:2)/ALG (1:20) equivalent dose)<10mg/kg

Exclusion Criteria:

• The expected survival period for multiple organ failure is no more than 3 months
• Not signing the informed consent form

The research results will be published in the form of an article in the future. Depending on the circumstances of the study, it may be possible to provide the relevant data upon request via email or other means.