Inclusion Criteria: Donors: Apheresis and Manufacturing

          -  Age ≥ 18 years old

          -  At least single haplotype matched (≥ 3/6) family member

          -  HIV negative

          -  For females of childbearing age:

          -  Not pregnant as confirmed by negative serum or urine pregnancy test within 14 days
             prior to enrollment AND Not lactating with intent to breastfeed

        Regarding donation eligibility, is identified as either:

          1. Completed the process of donor eligibility determination as outlined in 21 CFR 1271
             and agency guidance; OR

          2. Does not meet 21 CFR 1271 eligibility requirements but has a declaration of urgent
             medical need completed by the principal investigator or physician sub-investigator per
             21 CFR 1271.

        Identified recipient with relapsed and/or refractory CD19-positive leukemia who is not
        suitable to receive autologous CD19-CAR T-cell therapy as defined by the following:

          1. Relapsed and/or refractory disease despite prior treatment with autologous CD19-CAR
             T-cell therapy

          2. History of prior autologous leukapheresis failure

          3. History of prior autologous CAR T-cell manufacturing failure

          4. Unable to undergo autologous leukapheresis in the opinion of the study PI (s):
             examples may include - patient small size/low weight, inadequate T-cell counts,
             rapidly progressive leukemia, clinical status not amenable to apheresis Inclusion
             Criteria: Treatment

               -  Age ≤ 21 years old

               -  Not suitable to receive autologous CD19-CAR T-cell therapy as defined in section
                  3.1.6

               -  Relapsed and/or refractory CD19-positive leukemia*: *CD19-positivity confirmed
                  within 2 months and after receipt of any CD19-directed therapy

        Refractory disease (defined as any of the following):

        1. Primary refractory disease despite at least 2 cycles of an intensive chemotherapy
        regimen designed to induce remission 2. Refractory disease despite salvage therapy

        Relapsed disease (defined as any of the following):

          1. 2nd or greater relapse

          2. Any relapse after allogeneic hematopoietic cell transplantation (HCT)

          3. 1st relapse if patient requires an allogeneic HCT as part of standard of care relapse
             therapy, but is found to be ineligible and/or unsuitable for HCT

        Inclusion Criteria:Patient cohorts:

          -  Cohort A: patient has previously received a HCT from the selected CAR T- cell donor

          -  Cohort B - patient has NOT previously received a HCT from the selected CAR T-cell
             donor.

          -  Detectable medullary CD19-positive leukemia

          -  Estimated life expectancy of ≥ 8 weeks

          -  Karnofsky or Lansky performance score ≥ 50 (Appendix A)

          -  No CNS-3 disease or any level of detectable leukemia in CNS with associated neurologic
             symptoms

        If history of allogeneic HCT (regardless of donor type), prior to planned CAR T- cell
        infusion, must meet the following criteria:

          1. ≥ 3 months from HCT

          2. have recovered from prior HCT therapy

          3. have no evidence of active GVHD within prior 2 months

          4. have not received a donor lymphocyte infusion (DLI) within the 28 days prior to
             planned CAR T-cell infusion • Adequate cardiac function: left ventricular ejection
             fraction ≥ 40% or shortening fraction ≥ 25%

             • EKG without evidence of clinically significant arrhythmia

             • Adequate renal function: creatinine clearance or radioisotope GFR

             ≥ 50 ml/min/1.73m2 (GFR ≥ 40 ml/min/1.73m2 if < 2 years of age)

             • Adequate pulmonary function: forced vital capacity (FVC) ≥ 50% of predicted value;
             or pulse oximetry ≥ 92% on room air if patient is unable to perform pulmonary function
             testing

             • Total bilirubin ≤ 3 times the upper limit of normal for age, except in subjects with
             Gilbert's syndrome

               -  Alanine aminotransferase (ALT) or aspartate aminotransferase (AST) ≤ 5 times the
                  upper limit of normal for age

               -  No history of HIV infection

               -  No evidence of severe, uncontrolled bacterial, viral or fungal infection

               -  Has recovered from all NCI CTAE grade III-IV, non-hematologic acute toxicities
                  from prior therapy

             For females of childbearing age:

        1. Not pregnant with negative serum or urine pregnancy test ≤ 7 days prior to enrollment
        AND Not lactating with intent to breastfeed

          -  If sexually active, agreement to use birth control until 6 months after CAR T-cell
             infusion

          -  No history of hypersensitivity reactions to murine protein-containing products

          -  Not receiving systemic steroids therapy exceeding the equivalent of 0.5 mg/kg/day of
             methylprednisolone ≤ 7 days prior to CAR T-cell infusion

          -  Not receiving systemic therapy ≤ 14 days prior to CAR T-cell infusion, which will
             interfere with the activity of the CAR T-cell product in vivo (in the opinion of the
             study PI(s))

          -  Not receiving intrathecal chemotherapy ≤ 7 days prior to CAR T-cell infusion

          -  Agreement to participate in long-term follow-up on protocol NCT00695279

        Exclusion Criteria:

        • NA