Inclusion Criteria

          1. Age≥18 years with hematological malignancies who have undergone allogeneic transplant
             for hematological malignancy and are ≥180 days post-transplant.

          2. Relapsed disease post-allogeneic transplant defined as follows i. Acute or Chronic
             Leukemia or myelodysplastic or myeloproliferative disorders or natural killer (NK)
             cell neoplasms: Bone marrow (BM) with ≥5% disease involvement or peripheral blood
             evidence of overt relapse ii. Lymphoma: BM evidence of relapsed/persistent disease or
             PET/CT or CT evidence of persistent/progressive lymphadenopathy consistent with active
             lymphoma. Active disease defined as nodal lesions ≥ 20 mm in the long axis or
             extranodal lesions≥10 mm in long and short axis or bone marrow involvement that is
             biopsy proven

          3. Karnofsky performance status ≥70 (See Appendix A for details)

          4. Creatinine Clearance≥60 ml/min

          5. Adequate hepatic function, defined as aspartate aminotransferase (AST) and alanine
             aminotransferase (ALT) ≤3 x upper limit of normal (ULN). Serum bilirubin and alkaline
             phosphatase ≤3x x ULN, or considered not clinically significant (e.g. Gilbert's or
             indirect hyperbilirubinemia) or felt to be due to underlying disease.

          6. Without evidence of active acute or chronic graft versus host disease (GVHD)

          7. Off all immunosuppression and corticosteroids (other than replacement dose steroids
             defined as equivalent to a maximum of 10 mg Prednisone daily) for ≥28 days from first
             treatment.

          8. Off all disease targeted treatments for ≥10 days to first treatment day

          9. Able to provide written informed consent

         10. Women of child-bearing potential and men must agree to use adequate contraception for
             the duration of study participation and for 120 days after the last treatment with
             nivolumab.

         11. No FDA approved, more appropriate therapies available for disease control as
             determined by the treating physician

        Exclusion Criteria

          1. Positive beta-human chorionic gonadotropin (HCG) in female of child-bearing potential

          2. Cluster of differentiation 3 (CD3) donor chimerism <5% within 4 weeks of starting
             study treatment

          3. Prior administration of donor lymphocyte infusion post-allogeneic transplant within
             the last 6 months of study treatment

          4. History of or active autoimmune disease, or other syndrome that requires systemic
             steroids.

          5. History of allergic reactions attributed to compounds of similar chemical or biologic
             composition to nivolumab.

          6. Uncontrolled or active infections on treatment

          7. Confirmed active human immunodeficiency virus (HIV), Hepatitis B or C infection.

          8. Presence of ≥grade 3 non-hematologic toxicities as per CTCAE version 5 from any
             previous treatment unless it is felt to be due to underlying disease.

          9. Concurrent use of investigational therapeutic agents or enrollment on another
             therapeutic clinical trial at any institution.

             a. Minimum of 4 weeks from last dose of investigational agent

         10. Prior exposure to PD-1 or CTLA4 antibodies in the post-allogeneic transplant setting.
             Participants who received such agents pre-allogeneic transplant will NOT be excluded.

         11. Prior exposure to daratumumab in the post-allogeneic transplant setting within two
             months of start date of treatment with this investigational protocol. Participants who
             received this agent pre-allogeneic transplant will NOT be excluded

         12. Concurrent therapies targeted at disease relapse. However, previous treatments for
             relapsed disease are allowed.

         13. Concurrent active malignancy (exceptions: treated solid malignancy in >2 years'
             remission, treated basal or squamous cell carcinomas of the skin)

         14. History of Crohn's disease or ulcerative colitis

         15. History of demyelinating disorder

         16. Prior intolerance or allergy to tocilizumab