The present study was a prospective one-arm clinical study, in which EBV-HLH/chronic active EBV infection patients were selected as the main subjects to evaluate the effect of PD-1 antibody and lenalidomide regimens on ebv-dna and safety.

Inclusion Criteria:

1. Patients with CAEBV confirmed by 2016 Revised World Health Organization classification.
2. If the patient has previously suffered CAEBV-HLH, the HLH should be in remission.
3. A woman of childbearing age must be determined not to be pregnant by a pregnancy test and is willing to take effective measures to prevent pregnancy during the trial period and ≥12 months after the last administration of the drug; All male subjects used contraceptive methods during the study period and ≥6 months after the last administration;
4. Ages Eligible for Study: 1 Year to 65 Years.
5. Sign the informed consent.

Exclusion Criteria:

1. Heart function above grade II (NYHA).
2. Pregnancy or lactating Women.
3. Allergic to PD-1 antibody or lenalidomide.
4. Active bleeding of the internal organs.
5. uncontrollable infection.
6. Participate in other clinical research at the same time.